Attogram is 1e-18 gram units.
Attograms to Kilograms Converter — ag to kg
Convert Attogram (ag) to Kilogram (kg) using the exact conversion factor (1 attogram = 1e-21 kilogram). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Attograms to Kilograms converter
Converter
Mass/Weight Converter
Convert SI mass, imperial weight, jewelry, atomic, and astronomy mass units.
Context values
Some unit families need one extra value for a physically accurate result.
Kilogram is 1000 gram units.
Result = input x 1e-21 / 1.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Attograms to Kilograms
Weight conversions between Attogram and Kilogram come up constantly in everyday commerce, shipping, and cooking, since US packaging is usually labeled in pounds while most of the rest of the world uses kilograms. Attogram is typically associated with used in specialized scientific measurement, not everyday contexts, while Kilogram is typically associated with used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound..
Formula
kilograms = attograms × 1e-21
This factor comes from each unit's defined relationship to the category's base unit: 1 attogram equals 1e-21 base units, and 1 kilogram equals 1 base unit, so dividing one by the other gives the direct attogram-to-kilogram factor of 1e-21.
Simple example
1 ag × 1e-21 = 1e-21 kg
1 attogram = 1e-21 kilograms.
Real-world example
50 ag × 1e-21 = 5e-20 kg
50 attograms = 5e-20 kilograms.
Conversion table
| Attogram (ag) | Kilogram (kg) |
|---|---|
| 1 ag | 1e-21 kg |
| 5 ag | 5e-21 kg |
| 10 ag | 1e-20 kg |
| 25 ag | 2.5e-20 kg |
| 50 ag | 5e-20 kg |
| 100 ag | 1e-19 kg |
Reverse conversion: Kilogram to Attogram
1e-21 kg × 1e+21 = 1 ag
1e-21 kilograms = 1 attograms.
attograms = kilograms × 1e+21
For a page dedicated to this direction, see Kilogram to Attogram.
Attogram vs. Kilogram
| Aspect | Attogram | Kilogram |
|---|---|---|
| Family | SI derived (metric prefix) unit | SI base unit |
| Typical use | Nanotechnology and single-molecule mass measurement | Pricing and labeling goods sold by weight in retail and commodity trade |
| Where it's used | Used in specialized scientific measurement, not everyday contexts | Used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound. |
Understanding the Attogram
Attogram (ag) measures mass. An attogram is 10⁻¹⁸ grams (10⁻²¹ kilograms) — 'atto-' is the SI prefix for one quintillionth. It is classified as a SI derived (metric prefix) unit.
Where it's used: Used in specialized scientific measurement, not everyday contexts
Uses of the Attogram today
- Nanotechnology and single-molecule mass measurement
- Analytical chemistry at extremely small mass scales
- Comparing against atomic-scale mass units like the atomic mass unit
History of the Attogram
The attogram is simply the gram combined with the SI prefix 'atto-' (10⁻¹⁸), one of the small-scale metric prefixes introduced by the International Committee for Weights and Measures as part of the broader SI prefix system, not a unit with its own separate history.
Historical origin. Attogram was not the invention of a single named person; it developed through the process described above.
Understanding the Kilogram
Kilogram (kg) measures mass. The kilogram is the SI base unit of mass; every other SI mass unit is a decimal multiple or fraction of it. It is classified as a SI base unit.
Where it's used: Used as the standard mass unit in nearly every country except the United States and a few others that primarily use the pound.
Uses of the Kilogram today
- Pricing and labeling goods sold by weight in retail and commodity trade
- Dosing calculations in medicine, especially for pediatric and weight-based prescriptions
- Structural and material specification in metric-system engineering
- Scientific measurement of mass across chemistry, physics, and materials research
History of the Kilogram
The kilogram's direct predecessor was the 'grave,' defined by the French Academy of Sciences in 1793 as the mass of one cubic decimeter of water at its temperature of maximum density. Because 'grave' echoed the aristocratic title 'graf,' revolutionary France's decree of 18 Germinal, Year III (7 April 1795) renamed the system: the gram became the reference unit, defined as the mass of one cubic centimeter of water at the melting point of ice, and the kilogram — one thousand grams — took over the grave's practical role.
Turning that water-based definition into a physical object required real experimental work: chemist Louis Lefèvre-Gineau was tasked in 1795 with measuring precisely how much a cubic decimeter of water weighed, and former royal jeweller Marc-Étienne Janety then fabricated a platinum cylinder to embody that measured mass. Deposited in the French National Archives in 1799, it became known as the Kilogramme des Archives.
The metric system spread unevenly — Napoleon briefly restricted its use — but France made it compulsory in 1840, and the 1875 Metre Convention (signed by seventeen nations including the US) established the BIPM and a shared international prototype. The platinum-iridium International Prototype of the Kilogram, adopted in 1889 and nicknamed 'Le Grand K,' served as the world's mass reference for over a century.
On 20 May 2019, the kilogram was redefined by fixing the Planck constant at exactly 6.62607015 × 10⁻³⁴ joule-seconds, so it can now be realized in a laboratory (via a Kibble balance) without reference to any physical object.
Historical origin. Kilogram was not the invention of a single named person; it developed through the process described above.
Attogram — sources
- BIPM SI Brochure — SI prefixes — Defines 'atto-' as the prefix for 10⁻¹⁸.
Kilogram — sources
- BIPM — The kilogram (SI base unit) — Official definition and history since the 2019 redefinition.
- NIST — Kilogram: The Past — History of the kilogram standard from the grave to the International Prototype Kilogram.
- SI Brochure, 9th edition (2019), Appendix 2 — BIPM — Official text of the Planck-constant-based definition of the kilogram.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilograms are in 1 attogram?
1 attogram equals 1e-21 kilograms, using the exact defined conversion factor rather than an estimate.
How do I convert attogram to kilogram?
Multiply the attogram value by 1e-21. The converter above does this instantly to whatever precision you set.
How do I convert kilogram back to attogram?
Use the reverse factor: 1 kilogram equals 1e+21 attograms. You can also use the swap control in the converter above to flip the direction instantly.
What is a attogram?
Attogram (ag) measures mass. An attogram is 10⁻¹⁸ grams (10⁻²¹ kilograms) — 'atto-' is the SI prefix for one quintillionth. It is classified as a SI derived (metric prefix) unit.
What is a kilogram?
Kilogram (kg) measures mass. The kilogram is the SI base unit of mass; every other SI mass unit is a decimal multiple or fraction of it. It is classified as a SI base unit.
Is the attogram to kilogram conversion exact?
Yes. Both attogram and kilogram are defined by fixed standards rather than physical artifacts, so the factor of 1e-21 used above is exact to as many digits as you choose to display.
Where is the attogram still used today?
Used in specialized scientific measurement, not everyday contexts