Convert Carats to Tonnes
1 carat is 2.00e-7 t. One carat is exactly 2e-7 tonnes.
One carat is 2.0000 × 10^-7 tonnes. To convert carats to tonnes, multiply by 2.0000 × 10^-7; to go the other way, divide by 2.0000 × 10^-7 or multiply by 5000000. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST Handbook 44. Exactly 200 milligrams, fixed by international agreement in 1907 after centuries of local carats.
Factor checked against the defining standard · How we check
- Carats × 2.0000 × 10^-7
1 * 0.00000020 t
1 carat in every weight unit
| Unit | Value | Exact factor |
|---|---|---|
| ounces | 0.00705479239 oz | × 0.00705479238992 |
| pounds | 0.0004409245244 lb | × 0.00044092452437 |
| stone | 0.00003149460888 st | × 0.0000314946088836 |
| US tons | 0.0000002204622622 ton | × 0.000000220462262185 |
| micrograms | 200,000 mcg | × 200,000 |
| milligrams | 200 mg | × 200 |
| centigrams | 20 cg | × 20 |
| grams | 0.2 g | × 0.2 |
| kilograms | 0.0002 kg | × 0.0002 |
| slugs | 0.00001370435317 slug | × 0.0000137043531714 |
| tonnes | 0.0000002 t | × 0.0000002 |
| carats (as entered) | 1 ct | — |
| troy ounces | 0.006430149314 ozt | × 0.00643014931373 |
| grains | 3.086471671 gr | × 3.08647167059 |
| long tons | 0.0000001968413055 LT | × 0.000000196841305522 |
Factors are entered by hand from NIST Handbook 44 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert carats to tonnes? The converter and the working
- 1.Take the measurement in carats.
- 2.Multiply by 2.0000 × 10^-7 — that is how many tonnes fit in one carat.
- 3.To go back the other way, divide by 2.0000 × 10^-7, or multiply by 5000000.
Worked example: 25 carats to tonnes
- Formula
- ct × 2.0000 × 10^-7 = t
- Arithmetic
- 25 × 2.0000 × 10^-7 = 0.000005 t
- Answer
- 25 ct = 0.000005 t
The factor is rounded for display; the figure above is computed from the full value.
Carats to tonnes conversion table
| Carats | Tonnes |
|---|---|
| 1 ct | 2.00e-7 t |
| 2 ct | 4.00e-7 t |
| 3 ct | 6.00e-7 t |
| 4 ct | 8.00e-7 t |
| 5 ct | 0.000001 t |
| 6 ct | 0.0000012 t |
| 7 ct | 0.0000014 t |
| 8 ct | 0.0000016 t |
| 9 ct | 0.0000018 t |
| 10 ct | 0.000002 t |
| 12 ct | 0.0000024 t |
| 15 ct | 0.000003 t |
| 20 ct | 0.000004 t |
| 25 ct | 0.000005 t |
| 50 ct | 0.00001 t |
| 100 ct | 0.00002 t |
| 200 ct | 0.00004 t |
| 300 ct | 0.00006 t |
| 500 ct | 0.0001 t |
| 1000 ct | 0.0002 t |
| 2000 ct | 0.0004 t |
| 5000 ct | 0.001 t |
| 10000 ct | 0.002 t |
What is a carat?
Exactly 200 milligrams, fixed by international agreement in 1907 after centuries of local carats. It weighs a gemstone; the karat that grades gold is a different word for a different thing — purity in twenty-fourths.
What is a tonne?
One thousand kilograms, also called the metric ton — 2,204.6 pounds.
How many tonnes are in a carat?
One carat is 2.0000 × 10^-7 tonnes. Going the other way, one tonne is 5000000 carats. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every weight unit here
The whole group — 15 units with their symbols and the size of each one in kilograms — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a carat.
Cite this page
- APA
- Rule Calculator. (2026). Convert Carats to tonnes. Rule Calculator. https://rulecalculators.com/convert/carat-to-tonne
- MLA
- "Convert Carats to tonnes." Rule Calculator, August 16, 2026, https://rulecalculators.com/convert/carat-to-tonne.
- Chicago
- Rule Calculator. "Convert Carats to tonnes." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/carat-to-tonne.
The date is when the figures on this page were last checked against their source, not the day you opened it. Add your own access date if your style needs one.
Questions people actually ask
- How many tonnes are in a carat?
- 2.0000 × 10^-7. One thousand kilograms, also called the metric ton — 2,204.6 pounds.
- How do I convert tonnes back to carats?
- Divide by 2.0000 × 10^-7, or multiply by 5000000 — they are the same operation.
Other weight conversions
Tonnes to carats — the same conversion the other way.