Enter carats or ounces into the calculator to convert to the other value, supporting carats, points, grams, and both avoirdupois and troy ounces.
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Carat to Ounces Formula
The calculator converts between carats and ounces by going through grams as the common base unit. One metric carat is exactly 0.2 grams. The ounce value depends on which ounce you pick.
ounces = (carats * 0.2) / g_per_oz
carats = (ounces * g_per_oz) / 0.2
- carats: weight in metric carats (ct)
- ounces: weight in the chosen ounce type
- g_per_oz: 28.349523125 g for an avoirdupois ounce, 31.1034768 g for a troy ounce
- 0.2: grams in one metric carat (fixed by international agreement, 1907)
Assumptions: the calculator uses the metric carat, not the older variable carat values. Points are 1/100 of a carat (0.002 g). Pounds use the avoirdupois pound (453.59237 g). Pick troy ounces when weighing precious metals like gold or silver. Pick avoirdupois ounces for everyday weight.
The two tabs swap the direction of the formula. The "Carats to ounces" tab applies the first equation and lets you change the input unit (carats, points, milligrams, grams) and the ounce type. The "Ounces to carats" tab applies the second equation and accepts avoirdupois ounces, troy ounces, pounds, or grams. The decimal places dropdown only changes display rounding, not the underlying calculation.
Reference Tables
Use these for quick checks before running the calculator.
| Carats | Grams | Avoirdupois oz | Troy oz |
|---|---|---|---|
| 1 ct | 0.2 | 0.007055 | 0.006430 |
| 5 ct | 1.0 | 0.035274 | 0.032151 |
| 25 ct | 5.0 | 0.176370 | 0.160754 |
| 100 ct | 20.0 | 0.705479 | 0.643015 |
| 141.7476 ct | 28.3495 | 1.000000 | 0.911458 |
| 155.5174 ct | 31.1035 | 1.097143 | 1.000000 |
| Use case | Pick this ounce | Why |
|---|---|---|
| Diamonds and gemstones | Avoirdupois | Stones are usually quoted in carats, but conversion to common ounces is the default outside the metals trade. |
| Gold, silver, platinum | Troy | Bullion markets use troy ounces. A troy oz is heavier than a regular oz. |
| Food, postage, retail | Avoirdupois | All standard US and UK weight uses this ounce. |
| Karat (gold purity) | Neither | Karat is a purity ratio, not a weight. Do not confuse with carat (ct). |
Worked Examples and FAQ
Example 1: A 2 ct diamond in ounces.
Grams: 2 × 0.2 = 0.4 g.
Avoirdupois ounces: 0.4 ÷ 28.349523125 = 0.014110 oz.
A 2 carat stone weighs about 0.0141 oz.
Example 2: A 1 oz gold coin in carats.
A 1 troy oz coin weighs 31.1034768 g.
Carats: 31.1034768 ÷ 0.2 = 155.5174 ct.
A standard 1 ozt gold coin is about 155.52 ct.
Example 3: 50 points to grams.
50 pt = 0.5 ct = 0.1 g. That is the weight of a half-carat stone.
Is a carat the same as a karat? No. Carat (ct) is the weight of a gemstone. Karat (kt) is the purity of gold, where 24 kt is pure gold.
Why are there two ounce values? The avoirdupois ounce (28.35 g) is the common ounce. The troy ounce (31.10 g) is used only for precious metals and gunpowder. They are not interchangeable. A troy ounce is roughly 10 percent heavier.
How accurate is the conversion? The constants used (0.2 g per carat, 28.349523125 g per avoirdupois ounce, 31.1034768 g per troy ounce) are exact by definition. Any error in your result comes from rounding the displayed decimals or from the precision of your input weight.
What is a point? A point is 1/100 of a carat. A 0.25 ct stone is a 25 point stone. Jewelers use points so they can describe small stones without decimals.
How many carats are in an ounce? One avoirdupois ounce holds about 141.7476 carats. One troy ounce holds about 155.5174 carats.
