Convert Deci to Atto

Deci (d) to Atto (a) SI prefix 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.

Value

From

Result

1 d = 1E+17 a

1 Deci = 1E+17 Atto

1 Atto = 1E-17 Deci

1 d in every supported prefix

Conversion chart: Deci to Atto

Conversion table

Deci (d)	Atto (a)
0.01 d	1E+15 a
0.1 d	1E+16 a
1 d	1E+17 a
2 d	2E+17 a
3 d	3E+17 a
5 d	5E+17 a
10 d	1E+18 a
20 d	2E+18 a
50 d	5E+18 a
100 d	1E+19 a
1000 d	1E+20 a

Deci (d)

Definition: An SI prefix denoting a factor of 10⁻¹ — one tenth of the base unit.

History: One of the original six metric prefixes adopted in France in 1795, from the Latin 'decimus' (tenth).

Current use: Most familiar in the deciliter (common in European recipes and beverage serving sizes) and the decibel, a logarithmic (not linear-prefix) unit that borrows the name.

Atto (a)

Definition: An SI prefix denoting a factor of 10⁻¹⁸ — one quintillionth of the base unit. From the Danish/Norwegian 'atten' (eighteen).

History: Adopted by the CGPM in 1964 alongside femto-, extending the SI down to the sub-atomic measurement scale.

Current use: Used in high-precision physics measurements, including attosecond-scale laser pulses used to study electron motion within atoms.

Supported Units

Prefix	Symbol	Multiplier (× base)
Yotta	Y	1E+24
Zetta	Z	1E+21
Exa	E	1E+18
Peta	P	1E+15
Tera	T	1E+12
Giga	G	1E+09
Mega	M	1000000
Kilo	k	1000
Hecto	h	100
Deka	da	10
None (base unit)	—	1
Deci	d	0.1
Centi	c	0.01
Milli	m	0.001
Micro	µ	1E-06
Nano	n	1E-09
Pico	p	1E-12
Femto	f	1E-15
Atto	a	1E-18
Zepto	z	1E-21
Yocto	y	1E-24

About These Parameters

Value: The number of "From" prefix units you want to re-express in the "To" prefix. Since prefixes are just multiplier scales, this value can represent anything from a physical quantity's leading digits to a plain abstract number.
From Unit: The SI prefix your value is currently scaled by — for example, the "kilo" in "kilogram" or the "nano" in "nanosecond," entered here without the base unit attached.
To Unit: The SI prefix you want the value re-expressed in. Use the swap button to flip From and To instantly, handy when converting a datasheet figure from one prefix scale to another.

How Prefix Conversion Works

The Formula

Every SI prefix is defined by a fixed power-of-ten multiplier relative to the unprefixed base value. To convert a value from one prefix scale to another:

result = value × (multiplier of "From" prefix ÷ multiplier of "To" prefix)

For Deci → Atto: multiply by 1E+17. For example, 1 d × 1E+17 = 1E+17 a.

A History of Powers of Ten

The original six metric prefixes — kilo, hecto, deka, deci, centi, milli — were adopted by the French Academy of Sciences in 1795 alongside the metric system itself. As science and industry needed to describe ever-larger and ever-smaller quantities, the CGPM (Conférence Générale des Poids et Mesures) extended the table repeatedly: mega and micro in 1960 when the modern SI was formalized, giga and nano the same year, tera and pico following soon after, then peta/femto (1975), exa/atto (1975), and finally zetta/zepto and yotta/yocto in 1991 — the classical range covered on this page. In 2022 the CGPM went further still, adding ronna/ronto and quetta/quecto to keep pace with data-storage and astrophysical quantities that had begun to outgrow even yotta.

Why a Prefix-Only Converter Is Useful

Every other unit converter on this site attaches these same prefixes to one specific base unit — grams, watts, bytes, farads — because that's how the prefix is actually used in practice. But the underlying math of "how much bigger is giga than mega" never changes no matter which unit it's modifying, so it's often faster to reason about the prefix scale on its own: quickly checking that a "giga" figure is a billion and not a million, or converting a "nano" measurement from one datasheet into the "micro" scale used by a different one, without needing to know or care what physical quantity either figure describes.

Example

1 d equals 1E+17 a. Whatever base unit these prefixes are actually attached to — grams, bytes, watts, seconds — the same multiplier ratio applies: 1 kilo- is always 1,000 times 1 (unprefixed), and 1 mega- is always 1,000 times 1 kilo-, regardless of the quantity being measured.

Frequently Asked Questions

How many Atto are in 1 Deci?

1 Deci (d) equals exactly 1E+17 Atto (a).

Is giga a billion or a million?

Giga is always a billion (10⁹) times the base unit — a common point of confusion is with "mega," which is a million (10⁶). The two are frequently mixed up in casual conversation about data storage and computing speed, which is exactly the kind of mistake this converter is designed to catch.

Does this converter work for any unit, like grams or bytes?

Yes — this converter deliberately ignores the underlying unit and works purely with the multiplier scale. "1 kilo- to mega-" gives the same ratio (0.001) whether you mentally attach it to grams, watts, bytes, or any other quantity, because the prefix's multiplier is independent of what it's modifying.

What does "None (base unit)" mean in the unit list?

"None (base unit)" represents a value with no prefix attached at all — a plain gram, meter, or watt rather than a kilogram, kilometer, or milliwatt. It's included so you can convert directly between an unprefixed value and any prefixed scale, such as figuring out how many kilo- units equal one plain (unprefixed) unit.

Are ronna, ronto, quetta, and quecto included here?

Not yet — this page covers the classical SI prefix range from yotta (10²⁴) down to yocto (10⁻²⁴), which was complete from 1991 until 2022. The newer 2022 additions (ronna/ronna-, quetta/quecto) sit beyond even yotta and yocto and aren't included in this table.

Convert Deci to Other Prefixes

Possible Prefix Conversions

Zepto to Deka Micro to Pico Peta to Yocto Femto to Micro Nano to Femto Centi to Mega Peta to Giga Kilo to Peta Kilo to Zepto Nano to Giga Deka to Nano Kilo to Mega Atto to Nano None (base unit) to Yotta Zepto to Mega Centi to Micro None (base unit) to Femto Hecto to Femto Pico to Hecto Deci to Atto Exa to Micro Micro to Yotta Exa to Milli Femto to Hecto Deci to None (base unit) Centi to Zepto Pico to None (base unit) None (base unit) to Centi Femto to Kilo Yocto to Kilo Zepto to Micro Yocto to Centi Deka to Micro Kilo to Yocto Zepto to Milli Tera to Kilo Zetta to Peta None (base unit) to Nano Deka to Peta Centi to Atto Giga to Femto Kilo to Zetta Micro to Zepto Milli to Deci Zepto to Giga Hecto to Nano Femto to Mega Centi to Yocto Mega to None (base unit) Pico to Zetta Milli to Zepto Micro to Peta Zetta to Femto Tera to Yocto Femto to Nano Deci to Exa Zetta to Yotta Femto to Tera Zetta to Mega Tera to Yotta Centi to Deci Peta to Micro Hecto to None (base unit) Peta to Milli Exa to None (base unit) Exa to Deci Mega to Zepto Zetta to Centi None (base unit) to Tera None (base unit) to Peta Femto to Zetta Milli to Nano Deci to Micro Atto to Giga Exa to Kilo Pico to Zepto Pico to Giga Centi to Giga Exa to Zepto None (base unit) to Zetta Deci to Tera Yocto to Femto Nano to Pico Deci to Zepto Tera to Milli Femto to Deka Zetta to Atto Deci to Yocto Femto to Atto Femto to Peta Milli to Hecto Deci to Giga Giga to None (base unit) Nano to Centi Femto to Yocto Femto to Milli Tera to Pico Kilo to Femto Deka to Hecto None (base unit) to Micro Yocto to Deci Exa to Yocto Mega to Micro Pico to Kilo Zepto to Pico Milli to Zetta Centi to Exa Kilo to Centi Giga to Yotta Atto to Exa Zepto to Deci Exa to Femto Micro to Centi Nano to Yotta Mega to Hecto Deka to Tera Yotta to Pico Tera to Nano Atto to Femto Yocto to Micro Hecto to Zetta Yotta to Zepto Yocto to Nano None (base unit) to Pico Pico to Yotta Deka to Femto Deci to Zetta Giga to Deci Yocto to Milli Nano to Kilo Zepto to Nano Giga to Hecto Micro to Exa Zepto to Centi Hecto to Centi Giga to Milli Femto to Yotta None (base unit) to Hecto Peta to Exa Zetta to Yocto Tera to Peta Pico to Tera Atto to Milli Femto to None (base unit) Peta to Atto Centi to Deka Yotta to Tera Tera to Hecto Milli to Tera Atto to Hecto Tera to Deci Zepto to Hecto Atto to Zepto Mega to Tera Nano to Zepto Micro to Deci Zetta to Deka Mega to Yocto Deka to Giga Zetta to Deci Micro to Tera Yotta to Peta Yotta to Deci Micro to Deka Atto to Kilo Nano to Micro Milli to Exa Exa to Atto Centi to Pico Kilo to Micro Zetta to Nano Yotta to Hecto Mega to Pico Hecto to Kilo Peta to Deka Tera to Mega Deci to Mega Mega to Kilo Yocto to Exa Hecto to Mega Deka to Zepto Mega to Yotta Pico to Nano Yotta to Centi Kilo to Deci Exa to Peta Pico to Femto Deci to Deka Yocto to Hecto Deka to Atto Zepto to Yocto Yocto to Tera Kilo to Exa Nano to None (base unit) Giga to Kilo Kilo to Giga Yocto to Atto Peta to Yotta Tera to Zetta Deka to Deci Deka to Pico Yocto to Mega Giga to Yocto Micro to Atto Milli to Deka Atto to Yocto Giga to Tera Deka to Yocto Kilo to Yotta Peta to Deci None (base unit) to Atto Tera to Atto Nano to Mega Hecto to Atto Centi to Hecto None (base unit) to Kilo Femto to Deci Nano to Deka Peta to Zetta None (base unit) to Giga Exa to Yotta Hecto to Deci Deka to Kilo Centi to Kilo Milli to Yotta Zetta to Micro Mega to Deci Zepto to Yotta Tera to Micro Exa to Centi Kilo to Deka Giga to Zetta Micro to Zetta Nano to Hecto Zepto to Zetta Pico to Atto Nano to Exa Zepto to Femto Pico to Mega Hecto to Yotta Exa to Tera Yocto to Giga Mega to Exa Atto to Centi Yocto to Yotta Exa to Mega Yocto to Zepto Zetta to Giga Yocto to Deka Exa to Giga Micro to None (base unit) Milli to Mega None (base unit) to Milli Yocto to Pico Micro to Femto None (base unit) to Deka Nano to Atto Atto to Tera Nano to Milli Zepto to Atto Atto to Deka Nano to Zetta Giga to Zepto Tera to Exa Peta to Kilo Hecto to Milli Deka to Zetta Tera to Femto Mega to Deka Deci to Centi Yotta to Mega Deka to None (base unit) Giga to Nano Milli to Centi Atto to Yotta Micro to Hecto Pico to Exa Yotta to Zetta Centi to Nano Centi to Femto Nano to Deci Peta to Hecto Milli to Giga Deci to Peta Zetta to Exa Femto to Giga Peta to Mega Micro to Nano Pico to Centi Pico to Micro Peta to Femto Yotta to Milli Milli to Atto Yotta to Exa Exa to Deka Centi to Yotta Yotta to Yocto Kilo to Pico Zepto to Exa Zetta to Tera Peta to Pico Hecto to Pico Mega to Nano None (base unit) to Exa Mega to Centi Hecto to Zepto Deka to Yotta Centi to Peta Femto to Pico Yocto to Peta Tera to Giga Giga to Mega None (base unit) to Yocto Mega to Zetta Giga to Micro Exa to Hecto Zepto to None (base unit) Hecto to Yocto Tera to Centi Tera to Deka Yotta to Deka Atto to Zetta Yotta to Atto Yocto to None (base unit) Milli to Pico Pico to Deka Atto to Pico Atto to Mega Zepto to Kilo Zepto to Tera Yocto to Zetta Nano to Peta Atto to None (base unit) Micro to Yocto Deci to Yotta Micro to Mega Milli to Femto Yotta to None (base unit) Milli to Yocto Peta to Tera None (base unit) to Deci Micro to Milli Zetta to Hecto Deci to Pico Peta to Centi Deka to Mega Atto to Peta Deka to Centi Nano to Tera Zetta to Milli Femto to Zepto Giga to Peta Milli to Micro Peta to Nano Deka to Milli Hecto to Tera Milli to Peta Centi to None (base unit) Centi to Tera Mega to Peta Zetta to Zepto Pico to Peta Yotta to Giga Kilo to Atto Exa to Pico Femto to Centi Yotta to Kilo Yotta to Femto Kilo to Nano Giga to Centi Hecto to Deka Pico to Yocto Zepto to Peta Mega to Atto Peta to None (base unit) Kilo to None (base unit) Mega to Giga Mega to Milli Giga to Exa Zetta to Pico Exa to Zetta Deci to Kilo Deci to Nano Hecto to Peta Zetta to Kilo Pico to Milli Hecto to Exa Micro to Kilo Hecto to Giga Deci to Femto Kilo to Tera Giga to Pico Yotta to Micro Femto to Exa Hecto to Micro None (base unit) to Mega Atto to Micro Deci to Milli Pico to Deci Nano to Yocto Kilo to Hecto Kilo to Milli Micro to Giga Deka to Exa Giga to Deka Yotta to Nano Giga to Atto Zetta to None (base unit) Centi to Milli Atto to Deci Milli to Kilo Exa to Nano Tera to None (base unit) Centi to Zetta Peta to Zepto Deci to Hecto Mega to Femto Tera to Zepto None (base unit) to Zepto Milli to None (base unit)