A gram is one thousandth of a kilogram.
Grams to Attograms Converter — g to ag
Convert Gram (g) to Attogram (ag) using the exact conversion factor (1 gram = 1e+18 attogram). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Grams to Attograms 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.
Attogram is 1e-18 gram units.
Result = input x 0.001 / 1e-21.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Grams to Attograms
Weight conversions between Gram and Attogram 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. Gram is typically associated with standard small-mass unit worldwide, while Attogram is typically associated with used in specialized scientific measurement, not everyday contexts.
Formula
attograms = grams × 1e+18
This factor comes from each unit's defined relationship to the category's base unit: 1 gram equals 0.001 base units, and 1 attogram equals 1e-21 base units, so dividing one by the other gives the direct gram-to-attogram factor of 1e+18.
Simple example
1 g × 1e+18 = 1e+18 ag
1 gram = 1e+18 attograms.
Real-world example
50 g × 1e+18 = 5e+19 ag
50 grams = 5e+19 attograms.
Conversion table
| Gram (g) | Attogram (ag) |
|---|---|
| 1 g | 1e+18 ag |
| 5 g | 5e+18 ag |
| 10 g | 1e+19 ag |
| 25 g | 2.5e+19 ag |
| 50 g | 5e+19 ag |
| 100 g | 1e+20 ag |
Reverse conversion: Attogram to Gram
1e+18 ag × 1e-18 = 1 g
1e+18 attograms = 1 gram.
grams = attograms × 1e-18
For a page dedicated to this direction, see Attogram to Gram.
Gram vs. Attogram
| Aspect | Gram | Attogram |
|---|---|---|
| Family | SI derived (metric prefix) unit | SI derived (metric prefix) unit |
| Typical use | Cooking and nutrition labeling worldwide (including in the US, alongside ounces) | Nanotechnology and single-molecule mass measurement |
| Where it's used | Standard small-mass unit worldwide | Used in specialized scientific measurement, not everyday contexts |
Understanding the Gram
Gram (g) measures mass. A gram is one-thousandth of a kilogram, the SI base unit of mass. It is classified as a SI derived (metric prefix) unit.
Where it's used: Standard small-mass unit worldwide
Uses of the Gram today
- Cooking and nutrition labeling worldwide (including in the US, alongside ounces)
- Precious metal and small-item weighing
- Scientific and laboratory measurement
History of the Gram
Originally defined in 1795 as the mass of one cubic centimeter of water, the gram follows directly from the kilogram (1/1000 of it) under the modern SI system, inheriting the kilogram's various historical and current definitions.
Historical origin. Gram was not the invention of a single named person; it developed through the process described above.
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.
Gram — sources
- BIPM — The kilogram (SI base unit) — Basis for the gram as 1/1000 of the kilogram.
Attogram — sources
- BIPM SI Brochure — SI prefixes — Defines 'atto-' as the prefix for 10⁻¹⁸.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many attograms are in 1 gram?
1 gram equals 1e+18 attograms, using the exact defined conversion factor rather than an estimate.
How do I convert gram to attogram?
Multiply the gram value by 1e+18. The converter above does this instantly to whatever precision you set.
How do I convert attogram back to gram?
Use the reverse factor: 1 attogram equals 1e-18 grams. You can also use the swap control in the converter above to flip the direction instantly.
What is a gram?
Gram (g) measures mass. A gram is one-thousandth of a kilogram, the SI base unit of mass. It is classified as a SI derived (metric prefix) unit.
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.
Is the gram to attogram conversion exact?
Yes. Both gram and attogram are defined by fixed standards rather than physical artifacts, so the factor of 1e+18 used above is exact to as many digits as you choose to display.
Where is the gram still used today?
Standard small-mass unit worldwide