One metric carat equals exactly 0.2 g, so to convert carat to grams you divide the carat number by 5. One ounce is about 28.35 g, which makes an ounce roughly 141.7 carats.
| Carats | Grams |
|---|---|
| 1 ct | 0.2 g |
| 5 ct | 1.0 g |
| 10 ct | 2.0 g |
| 25 ct | 5.0 g |
| 50 ct | 10.0 g |
| 100 ct | 20.0 g |
What each unit means
Grams (g) are the everyday metric unit and the easiest to work with in a kitchen. Recipes, nutrition labels and coffee ratios all speak grams.
Ounces (oz) on a kitchen scale are avoirdupois ounces. The National Institute of Standards and Technology (NIST) lists one at 28.349523 g, which rounds to 28.35 g. Sixteen of them make a pound, about 453.6 g.
Carats (ct) are used for gemstones. NIST notes the carat started out as the weight of a carob seed and was later standardized at 0.2 g, or 200 mg. Don't confuse it with karat, spelled with a k, which describes the purity of gold, not its weight.
Grains (gr) are a very small unit, exactly 64.79891 mg, or about 0.0648 g.
Converting carat to grams and back
The math is friendly because 0.2 is a clean number:
- Carats to grams: multiply by 0.2, or divide by 5. So 35 ct is 7 g.
- Grams to carats: multiply by 5. So 3 g is 15 ct.
- Ounces to carats: 28.35 g times 5 is about 141.7 ct per ounce.
Here's a handy detail if your display reads in 0.1 g steps. Each step is half a carat, because 0.1 g times 5 is 0.5 ct. So when you convert a gram reading to carats, the answer moves in 0.5 ct jumps. For jewelry appraisals or buying gems, use a jeweler's scale and a professional, not a kitchen tool.
Troy ounces and other units you might see
| Unit | In grams |
|---|---|
| 1 grain (gr) | 0.0648 g |
| 1 carat (ct) | 0.2 g |
| 1 pennyweight (dwt) | 1.555 g |
| 1 ounce (oz) | 28.35 g |
| 1 troy ounce (ozt) | 31.1 g |
| 1 pound (lb) | 453.6 g |
The troy ounce is the one that trips people up. Precious metals are priced in troy ounces, which are about 31.1 g, heavier than the 28.35 g ounce your kitchen scale uses. If a scale offers both oz and ozt, make sure you're on the right one before you write a number down.
Which unit to use in the kitchen
Grams, nearly every time. They're small enough for a pinch of yeast and big enough for a bag of flour, and you never have to deal with fractions. A reading of 4.1 g is clearer than 0.14 oz, and recipes written in grams are easy to scale up or down.
Ounces are fine if your recipe uses them. Just don't mix units halfway through. If you switch from grams to ounces in the middle of a recipe, write down which unit each number came from.
A practical tip: a MeasureMate digital measuring spoon switches between grams, ounces and other units with a button press, reads in 0.1 g steps, and weighs up to 500 g. Glance at the unit label on the display before you start, then press tare to zero the reading and scoop.
Quick questions
How many carats are in a gram?
Five. One carat is 0.2 g, so 1 g equals 5 ct.
How many grams are in an ounce?
About 28.35 g in a regular ounce. A troy ounce, used for precious metals, is about 31.1 g.
How many ounces can a 500 g scale weigh?
About 17.6 oz, since 500 divided by 28.35 is roughly 17.6. In carats that's 2,500 ct.
Weights based on NIST Special Publication 811 conversion factors and the NIST Office of Weights and Measures.