A metric carat is exactly 200 milligrams.
Carats to Attograms Converter — ct to ag
Convert Carat (ct) to Attogram (ag) using the exact conversion factor (1 carat = 2e+17 attogram). See the formula, worked examples, conversion table, history, and common uses.
Carats 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 0.0002 / 1e-21.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Carats to Attograms
Weight conversions between Carat 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. Specifically: A metric carat is exactly 200 milligrams, and attogram is 1e-18 gram units.
Formula
attograms = carats × 2e+17
This factor comes from each unit's defined relationship to the category's base unit: 1 carat equals 0.0002 base units, and 1 attogram equals 1e-21 base units, so dividing one by the other gives the direct carat-to-attogram factor of 2e+17.
Simple example
1 ct × 2e+17 = 2e+17 ag
1 carat = 2e+17 attograms.
Real-world example
50 ct × 2e+17 = 1e+19 ag
50 carats = 1e+19 attograms.
Conversion table
| Carat (ct) | Attogram (ag) |
|---|---|
| 1 ct | 2e+17 ag |
| 5 ct | 1e+18 ag |
| 10 ct | 2e+18 ag |
| 25 ct | 5e+18 ag |
| 50 ct | 1e+19 ag |
| 100 ct | 2e+19 ag |
Reverse conversion: Attogram to Carat
2e+17 ag × 5e-18 = 1 ct
2e+17 attograms = 1 carat.
carats = attograms × 5e-18
For a page dedicated to this direction, see Attogram to Carat.
Understanding the Carat (ct)
A metric carat is exactly 200 milligrams.
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.
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 carat?
1 carat equals 2e+17 attograms, using the exact defined conversion factor rather than an estimate.
How do I convert carat to attogram?
Multiply the carat value by 2e+17. The converter above does this instantly to whatever precision you set.
How do I convert attogram back to carat?
Use the reverse factor: 1 attogram equals 5e-18 carats. You can also use the swap control in the converter above to flip the direction instantly.
What is a carat?
Carat (ct) is a unit of mass/weight.
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 carat to attogram conversion exact?
Yes. Both carat and attogram are defined by fixed standards rather than physical artifacts, so the factor of 2e+17 used above is exact to as many digits as you choose to display.