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Convert Watts per Square Centimeter per Steradian (at 555 nm) to Apostilbs

Watt per Square Centimeter per Steradian (at 555 nm) (W/cm²/sr) to Apostilb (asb) luminance conversion — enter any value below to get an instant result, or use the table for common values.

Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.

The numeric value you want to convert. Decimals are accepted.

Result

1 Watt per Square Centimeter per Steradian (at 555 nm) = 21457078 Apostilbs

1 Apostilb = 4.66047E-08 Watts per Square Centimeter per Steradian (at 555 nm)

1 W/cm²/sr in every supported unit

Conversion chart: Watt per Square Centimeter per Steradian (at 555 nm) to Apostilbs

Conversion table

Watt per Square Centimeter per Steradian (at 555 nm) (W/cm²/sr) Apostilb (asb)
0.01 W/cm²/sr 214570.78 asb
0.1 W/cm²/sr 2145707.8 asb
1 W/cm²/sr 21457078 asb
2 W/cm²/sr 42914156 asb
3 W/cm²/sr 64371233 asb
5 W/cm²/sr 1.0728539E+08 asb
10 W/cm²/sr 2.1457078E+08 asb
20 W/cm²/sr 4.2914156E+08 asb
50 W/cm²/sr 1.07285E+09 asb
100 W/cm²/sr 2.14571E+09 asb
1000 W/cm²/sr 2.14571E+10 asb

Watt per Square Centimeter per Steradian (at 555 nm) (W/cm²/sr)

Definition: A radiometric luminance unit expressing radiant power per unit area per unit solid angle at 555 nanometers — the wavelength of peak human eye sensitivity — used to convert directly between physical radiant power and perceived brightness.

History: Defined using the luminous efficacy constant (683 lumens per watt at 555 nm, the photopic peak of human vision) that bridges radiometry (physical energy) and photometry (perceived brightness) at the single wavelength where the eye is most sensitive.

Current use: Used in laser safety calculations, optical radiometry, and calibration work where a source's physical radiant power must be related precisely to its perceived luminance.

Apostilb (asb)

Definition: A CGS-system luminance unit defined so that a perfectly diffusing surface illuminated at one lux has a luminance of one apostilb — related to the lambert by a factor of 10,000.

History: Introduced in early 20th-century European photometry (the name from Greek "apo-" plus "stilb") as a more conveniently scaled alternative to the stilb for typical illuminated, rather than self-luminous, surfaces.

Current use: Still used in some European ophthalmology and vision science literature, particularly in perimetry equipment that measures visual field sensitivity in apostilbs.

Supported Units

Unit Symbol In cd/m²
Candela per Square Meter cd/m² 1 cd/m²
Candela per Square Centimeter cd/cm² 10000 cd/m²
Candela per Square Foot cd/ft² 10.76391 cd/m²
Candela per Square Inch cd/in² 1550.0031 cd/m²
Kilocandela per Square Meter kcd/m² 1000 cd/m²
Stilb sb 10000 cd/m²
Lumen per Square Meter per Steradian lm/m²/sr 1 cd/m²
Lumen per Square Centimeter per Steradian lm/cm²/sr 10000 cd/m²
Lumen per Square Foot per Steradian lm/ft²/sr 10.76391 cd/m²
Watt per Square Centimeter per Steradian (at 555 nm) W/cm²/sr 6830000 cd/m²
Nit nt 1 cd/m²
Millinit mnt 0.001 cd/m²
Lambert L 3183.0989 cd/m²
Millilambert mL 3.1830989 cd/m²
Foot-Lambert fL 3.4262591 cd/m²
Apostilb asb 0.31830989 cd/m²
Blondel bd 0.31830989 cd/m²
Bril bril 3.1831E-08 cd/m²
Skot sk 0.0003183099 cd/m²

About These Parameters

Value
The luminance value you want to convert, expressed in the "From" unit. Accepts decimals, so you can enter anything from a faint scotopic reading in skots to a display's rated brightness in nits.
From Unit
The unit your input value is currently measured in — a monitor spec sheet's nits, a cinema calibration report's foot-lamberts, or a scientific instrument's candela per square meter.
To Unit
The unit you want the result converted into. Use the swap button to flip From and To instantly and compare figures across display, cinema, and scientific contexts.

How Luminance Conversion Works

The Formula

Every unit here is defined by a fixed multiplier relative to candela per square meter. To convert a value from one unit to another:

result = value × (factor of "From" unit ÷ factor of "To" unit)

For Watt per Square Centimeter per Steradian (at 555 nm) → Apostilb: multiply by 21457078. For example, 1 W/cm²/sr × 21457078 = 21457078 asb.

Nits vs. Candela per Square Meter

A nit and a candela per square meter are exactly the same physical quantity — "nit" is simply the shorter, everyday name adopted by the display and consumer electronics industry. When a phone, TV, or monitor spec sheet quotes "1,000 nits," that number is identical to 1,000 cd/m² in a scientific paper. The two names exist for context, not physics: engineers and physicists tend to write cd/m², while marketing copy, review sites, and display datasheets almost universally write nits.

CGS vs. SI Luminance Units

Several units on this page — the stilb, lambert, apostilb, blondel, bril, and skot — predate the modern SI system and come from the centimeter-gram-second (CGS) system of photometric units used in early 20th-century physics. They were built around the idea of a perfectly diffusing ("Lambertian") surface rather than the candela directly, which is why their conversion factors to cd/m² involve π-related constants (a lambert, for instance, equals 1/π candela per square centimeter). Most of these CGS units have been superseded by candela-per-square-meter and its nit alias in modern engineering, but they still surface in legacy scientific literature, older photometric instruments, and specialized fields like vision research that never fully migrated to SI.

Example

A luminance of 1 W/cm²/sr equals 21457078 asb. For scale, a typical smartphone screen runs around 500-1,000 nits, a calibrated cinema screen is set to roughly 14-16 foot-lamberts, an overcast sky reads around 2,000-4,000 cd/m², and the full moon's surface luminance is only about 2,500 cd/m² despite looking far brighter against a dark night sky.

Frequently Asked Questions

How many Apostilbs are in 1 Watt per Square Centimeter per Steradian (at 555 nm)?

1 Watt per Square Centimeter per Steradian (at 555 nm) (W/cm²/sr) equals exactly 21457078 Apostilbs (asb).

What's the difference between luminance and brightness?

Luminance is the objective, physically measured quantity — candela per square meter, or nits — while "brightness" is often used loosely to describe the subjective perception of how light a surface looks, which also depends on surrounding contrast and the viewer's eye adaptation. Luminance is what a light meter measures; brightness is what a person reports seeing.

Is a nit the same as a candela per square meter?

Yes — a nit and a candela per square meter (cd/m²) are exactly the same unit under two different names. "Nit" is the informal name used throughout the display and consumer electronics industry, while cd/m² is the formal SI name used in scientific and engineering contexts.

Why do cinema screens use foot-lamberts instead of nits?

The film and projection industry standardized on foot-lamberts decades before nits became common in consumer electronics, and SMPTE calibration standards for theatrical and home-theater screens (typically 14-16 foot-lamberts) are still written in that unit today. Converting to nits (1 fL ≈ 3.43 cd/m²) shows that cinema screens are actually much dimmer than a modern smartphone or TV display, which is intentional for a dark viewing room.

Why are there so many old CGS luminance units like the stilb and apostilb?

Before the SI system standardized photometry around the candela and candela-per-square-meter in the mid-20th century, different countries and scientific traditions developed their own luminance units within the centimeter-gram-second (CGS) system — the stilb and lambert in general use, the apostilb and its French-system twin the blondel for illuminated surfaces, and the extremely small bril and skot for vision research into low-light perception. Most have fallen out of everyday use but still appear in older instruments, legacy literature, and specialized scientific fields.

How accurate are these conversions?

Every conversion factor used here is the exact, internationally recognized relationship between the underlying luminance units — results are limited only by floating-point display precision, not by rounded conversion constants.

Convert Watt per Square Centimeter per Steradian (at 555 nm) to Other Luminance Units

Possible Luminance Conversions

Skot to Watts per Square Centimeter per Steradian (at 555 nm) Lumen per Square Meter per Steradian to Candela per Square Inch Lumen per Square Centimeter per Steradian to Lumens per Square Meter per Steradian Lumen per Square Meter per Steradian to Candela per Square Centimeter Millilambert to Lumens per Square Meter per Steradian Blondel to Apostilbs Watt per Square Centimeter per Steradian (at 555 nm) to Lumens per Square Foot per Steradian Lambert to Candela per Square Meter Nit to Millinits Lumen per Square Foot per Steradian to Millinits Candela per Square Centimeter to Blondels Nit to Candela per Square Inch Kilocandela per Square Meter to Candela per Square Meter Candela per Square Centimeter to Lumens per Square Meter per Steradian Lumen per Square Centimeter per Steradian to Candela per Square Foot Kilocandela per Square Meter to Apostilbs Foot-Lambert to Brils Millilambert to Apostilbs Lumen per Square Centimeter per Steradian to Candela per Square Inch Bril to Candela per Square Meter Stilb to Nits Blondel to Nits Stilb to Lumens per Square Centimeter per Steradian Lambert to Lumens per Square Meter per Steradian Kilocandela per Square Meter to Stilbs Watt per Square Centimeter per Steradian (at 555 nm) to Lumens per Square Centimeter per Steradian Blondel to Stilbs Blondel to Candela per Square Meter Candela per Square Centimeter to Lamberts Candela per Square Centimeter to Nits Candela per Square Centimeter to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Meter to Lumens per Square Foot per Steradian Kilocandela per Square Meter to Skots Watt per Square Centimeter per Steradian (at 555 nm) to Brils Stilb to Lumens per Square Foot per Steradian Millinit to Brils Skot to Stilbs Millilambert to Lamberts Candela per Square Foot to Candela per Square Inch Candela per Square Meter to Apostilbs Candela per Square Foot to Nits Lumen per Square Centimeter per Steradian to Nits Blondel to Millilamberts Stilb to Watts per Square Centimeter per Steradian (at 555 nm) Nit to Candela per Square Meter Foot-Lambert to Lumens per Square Foot per Steradian Kilocandela per Square Meter to Lumens per Square Centimeter per Steradian Blondel to Lumens per Square Foot per Steradian Skot to Candela per Square Inch Bril to Nits Nit to Foot-Lamberts Stilb to Blondels Candela per Square Foot to Lumens per Square Centimeter per Steradian Candela per Square Centimeter to Lumens per Square Centimeter per Steradian Apostilb to Brils Bril to Lamberts Watt per Square Centimeter per Steradian (at 555 nm) to Nits Candela per Square Foot to Lamberts Candela per Square Meter to Blondels Millinit to Nits Candela per Square Centimeter to Millinits Candela per Square Meter to Nits Skot to Apostilbs Candela per Square Foot to Brils Candela per Square Foot to Lumens per Square Foot per Steradian Kilocandela per Square Meter to Blondels Candela per Square Foot to Skots Millilambert to Nits Candela per Square Meter to Lumens per Square Meter per Steradian Watt per Square Centimeter per Steradian (at 555 nm) to Skots Nit to Blondels Candela per Square Centimeter to Apostilbs Skot to Candela per Square Centimeter Millinit to Candela per Square Foot Millilambert to Watts per Square Centimeter per Steradian (at 555 nm) Apostilb to Millilamberts Candela per Square Foot to Candela per Square Centimeter Blondel to Brils Lumen per Square Meter per Steradian to Watts per Square Centimeter per Steradian (at 555 nm) Kilocandela per Square Meter to Nits Foot-Lambert to Candela per Square Foot Millinit to Apostilbs Stilb to Candela per Square Centimeter Lumen per Square Foot per Steradian to Candela per Square Foot Bril to Candela per Square Centimeter Candela per Square Centimeter to Brils Candela per Square Meter to Brils Candela per Square Centimeter to Candela per Square Meter Apostilb to Blondels Kilocandela per Square Meter to Foot-Lamberts Candela per Square Centimeter to Millilamberts Millinit to Lamberts Lumen per Square Centimeter per Steradian to Apostilbs Nit to Candela per Square Centimeter Skot to Millilamberts Skot to Millinits Apostilb to Lumens per Square Foot per Steradian Watt per Square Centimeter per Steradian (at 555 nm) to Millilamberts Candela per Square Inch to Lumens per Square Meter per Steradian Candela per Square Meter to Stilbs Lumen per Square Centimeter per Steradian to Candela per Square Meter Lumen per Square Centimeter per Steradian to Brils Bril to Kilocandela per Square Meter Skot to Brils Lambert to Brils Lumen per Square Meter per Steradian to Candela per Square Foot Candela per Square Inch to Millilamberts Kilocandela per Square Meter to Brils Millilambert to Blondels Millinit to Blondels Foot-Lambert to Apostilbs Stilb to Apostilbs Watt per Square Centimeter per Steradian (at 555 nm) to Foot-Lamberts Bril to Millilamberts Bril to Skots Millinit to Skots Stilb to Foot-Lamberts Kilocandela per Square Meter to Millinits Candela per Square Inch to Candela per Square Centimeter Lumen per Square Meter per Steradian to Skots Lambert to Foot-Lamberts Foot-Lambert to Watts per Square Centimeter per Steradian (at 555 nm) Nit to Watts per Square Centimeter per Steradian (at 555 nm) Lumen per Square Centimeter per Steradian to Watts per Square Centimeter per Steradian (at 555 nm) Foot-Lambert to Candela per Square Meter Skot to Lumens per Square Foot per Steradian Blondel to Lamberts Candela per Square Inch to Apostilbs Nit to Lumens per Square Foot per Steradian Lumen per Square Centimeter per Steradian to Lumens per Square Foot per Steradian Millinit to Candela per Square Centimeter Bril to Stilbs Foot-Lambert to Candela per Square Centimeter Lumen per Square Centimeter per Steradian to Lamberts Candela per Square Centimeter to Candela per Square Foot Lumen per Square Foot per Steradian to Apostilbs Lambert to Candela per Square Foot Lambert to Skots Lumen per Square Meter per Steradian to Kilocandela per Square Meter Millinit to Candela per Square Meter Candela per Square Inch to Skots Stilb to Lumens per Square Meter per Steradian Candela per Square Centimeter to Stilbs Watt per Square Centimeter per Steradian (at 555 nm) to Millinits Kilocandela per Square Meter to Lumens per Square Meter per Steradian Lumen per Square Centimeter per Steradian to Kilocandela per Square Meter Skot to Candela per Square Meter Millinit to Lumens per Square Meter per Steradian Millilambert to Candela per Square Meter Nit to Lumens per Square Meter per Steradian Blondel to Lumens per Square Meter per Steradian Candela per Square Inch to Lamberts Watt per Square Centimeter per Steradian (at 555 nm) to Lamberts Lumen per Square Meter per Steradian to Millilamberts Watt per Square Centimeter per Steradian (at 555 nm) to Candela per Square Inch Candela per Square Meter to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Foot to Stilbs Foot-Lambert to Nits Foot-Lambert to Kilocandela per Square Meter Candela per Square Inch to Lumens per Square Centimeter per Steradian Bril to Millinits Blondel to Candela per Square Foot Bril to Watts per Square Centimeter per Steradian (at 555 nm) Lumen per Square Meter per Steradian to Candela per Square Meter Foot-Lambert to Lamberts Candela per Square Inch to Nits Kilocandela per Square Meter to Lumens per Square Foot per Steradian Lambert to Kilocandela per Square Meter Millinit to Foot-Lamberts Blondel to Kilocandela per Square Meter Watt per Square Centimeter per Steradian (at 555 nm) to Candela per Square Centimeter Millilambert to Candela per Square Inch Lumen per Square Meter per Steradian to Apostilbs Apostilb to Nits Candela per Square Meter to Lamberts Candela per Square Meter to Candela per Square Inch Lumen per Square Centimeter per Steradian to Millilamberts Candela per Square Foot to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Centimeter to Foot-Lamberts Watt per Square Centimeter per Steradian (at 555 nm) to Candela per Square Meter Candela per Square Inch to Brils Skot to Kilocandela per Square Meter Lumen per Square Meter per Steradian to Foot-Lamberts Stilb to Candela per Square Inch Stilb to Kilocandela per Square Meter Millilambert to Millinits Lumen per Square Foot per Steradian to Lumens per Square Centimeter per Steradian Lumen per Square Meter per Steradian to Blondels Lumen per Square Centimeter per Steradian to Blondels Millilambert to Foot-Lamberts Foot-Lambert to Lumens per Square Centimeter per Steradian Millinit to Candela per Square Inch Nit to Brils Candela per Square Meter to Candela per Square Centimeter Foot-Lambert to Candela per Square Inch Blondel to Candela per Square Inch Bril to Lumens per Square Foot per Steradian Stilb to Millilamberts Foot-Lambert to Millilamberts Blondel to Candela per Square Centimeter Lumen per Square Foot per Steradian to Nits Candela per Square Foot to Millilamberts Lambert to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Foot to Kilocandela per Square Meter Lumen per Square Foot per Steradian to Candela per Square Meter Nit to Lumens per Square Centimeter per Steradian Nit to Stilbs Bril to Candela per Square Inch Candela per Square Inch to Foot-Lamberts Watt per Square Centimeter per Steradian (at 555 nm) to Blondels Lambert to Candela per Square Centimeter Candela per Square Inch to Candela per Square Foot Apostilb to Lumens per Square Centimeter per Steradian Candela per Square Meter to Skots Blondel to Foot-Lamberts Lumen per Square Foot per Steradian to Lumens per Square Meter per Steradian Bril to Candela per Square Foot Lambert to Lumens per Square Centimeter per Steradian Stilb to Millinits Candela per Square Foot to Candela per Square Meter Kilocandela per Square Meter to Candela per Square Inch Apostilb to Skots Millilambert to Candela per Square Foot Lumen per Square Meter per Steradian to Millinits Apostilb to Millinits Candela per Square Foot to Blondels Apostilb to Watts per Square Centimeter per Steradian (at 555 nm) Millilambert to Lumens per Square Foot per Steradian Candela per Square Foot to Millinits Candela per Square Centimeter to Candela per Square Inch Candela per Square Inch to Candela per Square Meter Skot to Foot-Lamberts Foot-Lambert to Blondels Apostilb to Candela per Square Meter Millinit to Lumens per Square Centimeter per Steradian Candela per Square Foot to Apostilbs Stilb to Brils Watt per Square Centimeter per Steradian (at 555 nm) to Lumens per Square Meter per Steradian Lumen per Square Foot per Steradian to Lamberts Lumen per Square Meter per Steradian to Nits Lambert to Lumens per Square Foot per Steradian Candela per Square Inch to Blondels Nit to Apostilbs Nit to Kilocandela per Square Meter Lumen per Square Foot per Steradian to Brils Kilocandela per Square Meter to Lamberts Stilb to Skots Lambert to Apostilbs Lumen per Square Meter per Steradian to Lumens per Square Centimeter per Steradian Blondel to Lumens per Square Centimeter per Steradian Bril to Apostilbs Millilambert to Candela per Square Centimeter Kilocandela per Square Meter to Millilamberts Lumen per Square Centimeter per Steradian to Candela per Square Centimeter Candela per Square Centimeter to Kilocandela per Square Meter Apostilb to Stilbs Bril to Foot-Lamberts Lumen per Square Meter per Steradian to Lamberts Lumen per Square Centimeter per Steradian to Skots Kilocandela per Square Meter to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Meter to Millilamberts Skot to Lamberts Lambert to Millinits Nit to Lamberts Lumen per Square Foot per Steradian to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Meter to Candela per Square Foot Apostilb to Kilocandela per Square Meter Lumen per Square Foot per Steradian to Millilamberts Millilambert to Stilbs Candela per Square Inch to Watts per Square Centimeter per Steradian (at 555 nm) Foot-Lambert to Lumens per Square Meter per Steradian Lumen per Square Foot per Steradian to Stilbs Lambert to Nits Apostilb to Lumens per Square Meter per Steradian Lumen per Square Centimeter per Steradian to Foot-Lamberts Millilambert to Kilocandela per Square Meter Candela per Square Foot to Foot-Lamberts Millinit to Lumens per Square Foot per Steradian Lambert to Stilbs Nit to Skots Lumen per Square Meter per Steradian to Brils Blondel to Watts per Square Centimeter per Steradian (at 555 nm) Millinit to Kilocandela per Square Meter Watt per Square Centimeter per Steradian (at 555 nm) to Kilocandela per Square Meter Bril to Lumens per Square Centimeter per Steradian Blondel to Skots Watt per Square Centimeter per Steradian (at 555 nm) to Candela per Square Foot Apostilb to Candela per Square Foot Lumen per Square Foot per Steradian to Foot-Lamberts Apostilb to Candela per Square Centimeter Candela per Square Inch to Lumens per Square Foot per Steradian Lumen per Square Meter per Steradian to Stilbs Lumen per Square Meter per Steradian to Lumens per Square Foot per Steradian Apostilb to Foot-Lamberts Lumen per Square Foot per Steradian to Candela per Square Centimeter Candela per Square Meter to Millinits Lambert to Blondels Bril to Lumens per Square Meter per Steradian Candela per Square Centimeter to Skots Foot-Lambert to Millinits Watt per Square Centimeter per Steradian (at 555 nm) to Apostilbs Millilambert to Skots Lumen per Square Centimeter per Steradian to Stilbs Millilambert to Brils Lumen per Square Foot per Steradian to Skots Skot to Nits Watt per Square Centimeter per Steradian (at 555 nm) to Stilbs Kilocandela per Square Meter to Candela per Square Foot Foot-Lambert to Skots Kilocandela per Square Meter to Candela per Square Centimeter Stilb to Lamberts Candela per Square Inch to Stilbs Candela per Square Meter to Foot-Lamberts Nit to Millilamberts Skot to Blondels Candela per Square Meter to Kilocandela per Square Meter Skot to Lumens per Square Centimeter per Steradian Candela per Square Inch to Millinits Stilb to Candela per Square Meter Nit to Candela per Square Foot Skot to Candela per Square Foot Lumen per Square Foot per Steradian to Kilocandela per Square Meter Skot to Lumens per Square Meter per Steradian Stilb to Candela per Square Foot Bril to Blondels Millinit to Watts per Square Centimeter per Steradian (at 555 nm) Candela per Square Centimeter to Lumens per Square Foot per Steradian Lambert to Candela per Square Inch Millinit to Millilamberts Blondel to Millinits Millilambert to Lumens per Square Centimeter per Steradian Millinit to Stilbs Foot-Lambert to Stilbs Lumen per Square Foot per Steradian to Candela per Square Inch Apostilb to Candela per Square Inch Lambert to Millilamberts Candela per Square Meter to Lumens per Square Centimeter per Steradian Candela per Square Inch to Kilocandela per Square Meter Apostilb to Lamberts Lumen per Square Foot per Steradian to Blondels Lumen per Square Centimeter per Steradian to Millinits Candela per Square Foot to Lumens per Square Meter per Steradian

See also