Grams to Ounces
Convert grams to ounces and back for cooking, post and precious metals — including the troy ounce for gold, which is heavier than the ordinary one.
One ounce is about 28.35 grams. These are weight ounces — fluid ounces measure volume and are a different unit.
| Grams | Ounces |
|---|---|
| 1 | 0.04 |
| 5 | 0.18 |
| 10 | 0.35 |
| 28 | 0.99 |
| 50 | 1.76 |
| 100 | 3.53 |
| 250 | 8.82 |
| 500 | 17.64 |
| 1000 | 35.27 |
The conversion factor here is exact — it is a definition, not a measurement
Since 1959 the international pound has been defined as exactly 0.45359237 kilograms. Divide by sixteen and an ounce is exactly 28.349523125 grams — a number with an exact decimal expansion, because nobody weighed it. It was declared. The factor this page multiplies by, 0.035273961949580414, is precisely the reciprocal of that figure to the last bit a computer can hold. So none of the error you can find on this page comes from the constant. All of it comes from the display.
Both boxes show 6 decimal places, and 6 decimals mean very different things at the two ends. An ounce is twenty-eight times a gram, so the same decimals buy 3 more significant figures on one side than the other.
| Convert | Shown as | Significant figures |
|---|---|---|
| 1 gram | 0.035274 oz | 5 |
| 1 ounce | 28.349523 g | 8 |
964 of the first 1000 whole grams do not survive a round trip
Type 1 into the grams box, read 0.035274 out of the ounces box, and type that back in: you get 1.000001 grams. Repeating that for every whole gram from 1 to 1000, 964 of them fail to come back. Going the other way, not one of the first 200 whole ounces fails. The two directions are not alike, because the smaller unit needs more decimals to hold the same relative precision and does not get them.
The failures are harmless and measuring them says why. Every one lands within 1.40e-5 grams of the input, which is under half of one display step in ounces converted back to grams (1.42e-5 g). The error is bounded by the rounding that caused it and cannot be anything else.
They also do not accumulate. I expected a one-directional drift — a fixed rounding step ought to push consistently one way — and there isn't one. 483 of the 964 come back high and 481 come back low, and the net error across all 1000 conversions is 4.0e-6 grams. Round-to-nearest is unbiased by construction, so chaining conversions cancels rather than compounds.
| Direction | Tested | Failed | High | Low |
|---|---|---|---|---|
| Grams → ounces → grams | 1000 | 964 | 483 | 481 |
| Ounces → grams → ounces | 200 | 0 | 0 | 0 |
“28 grams to the ounce” is 1.23% low at every quantity
The kitchen shorthand is a consistent underestimate, and the same one every time — it is a fixed proportional error, so it does not wash out at larger quantities, it scales with them. Dividing grams by 28 instead overstates by 1.25%. The two are not mirror images, because inverting a ratio does not invert its percentage.
| Ounces | Exact grams | At 28 g/oz | Short by | Error |
|---|---|---|---|---|
| 1 | 28.35 | 28 | 0.35 g | -1.23% |
| 4 | 113.40 | 112 | 1.40 g | -1.23% |
| 8 | 226.80 | 224 | 2.80 g | -1.23% |
| 12 | 340.19 | 336 | 4.19 g | -1.23% |
| 16 | 453.59 | 448 | 5.59 g | -1.23% |
A pound of flour measured this way is 5.59 grams light, which no recipe will notice. Scale it to a commercial batch, or apply it somewhere the ratio matters rather than the amount, and it stops being nothing. Going the other way, 100 g reads as 3.57 oz when the true figure is 3.53 oz.
How to use
- Type a value in grams or ounces.
- Read the result to the precision you need.
- Check whether you want ounces of weight or fluid ounces of volume.
- For gold and silver, use troy ounces, not the standard ounce.
Frequently asked questions
How many grams are in an ounce?
Exactly 28.349523125 grams for the avoirdupois ounce, the one used for food, post and body weight. Most people round it to 28.35 or simply 28, which is fine for cooking and not fine for anything sold by weight.
Is a troy ounce different?
Yes, and expensively so. A troy ounce, used for gold, silver and platinum, is 31.1035 grams — about 10% heavier than the standard ounce. Quoting a gold price per ordinary ounce rather than per troy ounce introduces a 10% error, which is why bullion is always specified as troy.
What is 100 grams in ounces?
3.527 ounces, or a little over three and a half. For recipes, 100 g of most dry ingredients sits close to a half cup by volume, though volume varies with the ingredient and weight does not — which is the whole argument for a kitchen scale.
Are fluid ounces the same as ounces?
No, and they are not even the same kind of quantity. An ounce measures weight; a fluid ounce measures volume. They coincide only for water, and only approximately, and only in the imperial system — the US fluid ounce and the imperial fluid ounce differ by 4% as well.
Why do recipes mix grams and ounces?
Because cookbooks are published across markets and often list both. The conversions are frequently rounded to convenient numbers rather than exact ones, so 8 oz might appear as 225 g in one book and 230 g in another. For baking, where ratios matter, follow one column throughout rather than mixing them.
How do I convert quickly in my head?
Divide grams by 30 for a rough ounce figure, or multiply ounces by 30 going the other way. 500 g divided by 30 is about 16.7 oz against a true 17.6 — around 5% low, so it works for a shopping estimate and not for a recipe.
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