Convert Degree Fahrenheit-seconds per Btu (th) to Degree Fahrenheit-seconds per Btu (IT)
Degree Fahrenheit-second per Btu (th) (°F·s/Btu(th)) to Degree Fahrenheit-second per Btu (IT) (°F·s/Btu) thermal resistance 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.
Result
1 °F·s/Btu(th) = 1.0006692 °F·s/Btu
1 Degree Fahrenheit-second per Btu (th) = 1.0006692 Degree Fahrenheit-seconds per Btu (IT)
1 Degree Fahrenheit-second per Btu (IT) = 0.9993312 Degree Fahrenheit-seconds per Btu (th)
1 °F·s/Btu(th) in every supported unit
Conversion chart: Degree Fahrenheit-second per Btu (th) to Degree Fahrenheit-seconds per Btu (IT)
Conversion table
| Degree Fahrenheit-second per Btu (th) (°F·s/Btu(th)) | Degree Fahrenheit-second per Btu (IT) (°F·s/Btu) |
|---|---|
| 0.01 °F·s/Btu(th) | 0.010006692 °F·s/Btu |
| 0.1 °F·s/Btu(th) | 0.10006692 °F·s/Btu |
| 1 °F·s/Btu(th) | 1.0006692 °F·s/Btu |
| 2 °F·s/Btu(th) | 2.0013385 °F·s/Btu |
| 3 °F·s/Btu(th) | 3.0020077 °F·s/Btu |
| 5 °F·s/Btu(th) | 5.0033462 °F·s/Btu |
| 10 °F·s/Btu(th) | 10.006692 °F·s/Btu |
| 20 °F·s/Btu(th) | 20.013385 °F·s/Btu |
| 50 °F·s/Btu(th) | 50.033462 °F·s/Btu |
| 100 °F·s/Btu(th) | 100.06692 °F·s/Btu |
| 1000 °F·s/Btu(th) | 1000.6692 °F·s/Btu |
Degree Fahrenheit-second per Btu (th) (°F·s/Btu(th))
Definition: The thermochemical-Btu, per-second variant of the same unit family, differing from the IT-Btu version by the same small factor as their hour-based counterparts.
History: Follows the same International-Table-versus-thermochemical Btu split as the hour-based units, applied to the second-based time scale.
Current use: Rarely used outside of specialized thermochemistry calculations that explicitly require the thermochemical Btu definition.
Degree Fahrenheit-second per Btu (IT) (°F·s/Btu)
Definition: The same US thermal resistance concept as °F·h/Btu but scaled to seconds instead of hours, for contexts working with instantaneous rather than hourly heat rates.
History: A natural time-unit variant of °F·h/Btu, used wherever heat-flow calculations are expressed per second (matching the watt's own per-second basis) rather than per hour.
Current use: Used in scientific and short-duration engineering calculations that need a Fahrenheit/Btu-based resistance figure consistent with second-based power units.
Supported Units
| Unit | Symbol | In Kelvin per Watt |
|---|---|---|
| Kelvin per Watt | K/W | 1 K/W |
| Degree Celsius per Watt | °C/W | 1 K/W |
| Degree Fahrenheit-hour per Btu (IT) | °F·h/Btu | 1.8956342 K/W |
| Degree Fahrenheit-hour per Btu (th) | °F·h/Btu(th) | 1.8969028 K/W |
| Degree Fahrenheit-second per Btu (IT) | °F·s/Btu | 0.0005265651 K/W |
| Degree Fahrenheit-second per Btu (th) | °F·s/Btu(th) | 0.0005269175 K/W |
About These Parameters
- Value
- The thermal resistance value you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in — an electronics datasheet's K/W or °C/W, or a US insulation R-value's °F·h/Btu.
- To Unit
- The thermal resistance unit you want the result converted into. Use the swap button to flip From and To instantly.
How Thermal Resistance Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to kelvin per watt. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Degree Fahrenheit-second per Btu (th) → Degree Fahrenheit-second per Btu (IT): multiply by 1.0006692. For example, 1 °F·s/Btu(th) × 1.0006692 = 1.0006692 °F·s/Btu.
Predicting a Chip's Temperature
Electronics datasheets specify a component's thermal resistance (often junction-to-ambient, RθJA) in K/W or °C/W. Multiplying that figure by the power the component actually dissipates gives the temperature rise above ambient — a 50°C/W chip dissipating 0.5 W will run about 25°C hotter than the surrounding air. This is the calculation behind every heat-sink sizing decision in electronics design.
Thermal Resistance vs. R-value
US building insulation is rated with an "R-value" expressed in °F·h·ft²/Btu — technically a resistance per unit AREA rather than a single-point resistance like K/W, since insulation performance scales with how much wall or roof area it covers. This page handles the per-watt (not per-area) form of thermal resistance used in electronics and single-component heat-transfer calculations; the site's Heat Transfer Coefficient Converter covers the closely related per-area quantity used in building and HVAC engineering.
Example
A thermal resistance of 1 °F·s/Btu(th) equals 1.0006692 °F·s/Btu. For scale, a typical unheatsinked small transistor package might have a junction-to-ambient resistance around 60-100°C/W, while a well-designed heat sink can bring that down to just a few °C/W.
Frequently Asked Questions
How many Degree Fahrenheit-seconds per Btu (IT) are in 1 Degree Fahrenheit-second per Btu (th)?
1 Degree Fahrenheit-second per Btu (th) (°F·s/Btu(th)) equals exactly 1.0006692 Degree Fahrenheit-seconds per Btu (IT) (°F·s/Btu).
Why are K/W and °C/W numerically identical?
Thermal resistance is an interval-based quantity (a temperature DIFFERENCE per watt), and a one-kelvin difference is exactly the same size as a one-degree-Celsius difference. The fixed offset between the Kelvin and Celsius scales cancels out completely, so the two units are always numerically equal.
What's the difference between the two Btu-based units on this page?
"IT" refers to the International Table Btu, based on the international steam-table calorie; "th" refers to the thermochemical Btu, based on the thermochemical calorie. They differ by less than 0.1%, which rarely matters in practice, but scientific and engineering references sometimes specify one explicitly.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized relationship between the underlying temperature and energy units — results are limited only by floating-point display precision, not by rounded conversion constants.