Ounces to Grams Converter

ounces to grams — quick reference

The formula, worked line by line

This conversion is a multiplication by a constant that was chosen, not discovered. Before 1959 the United States and the United Kingdom each maintained a pound against their own physical prototype, and the two differed slightly. The International Yard and Pound Agreement replaced both with one exact figure, and every ounce, grain and stone now falls out of it by simple division.

Split that pound sixteen ways and the ounce is exactly 28.349523125 grams. The decimal terminates because 0.45359237 kilograms divided by 16 terminates, which is the whole appeal of a defined constant: the conversion introduces no error of its own, and any inaccuracy in your answer came from the scale rather than the arithmetic.

grams = ounces × 28.349523125
28.349523125 = 453.59237 ÷ 16   (the pound, split sixteen ways)
8 oz → 8 × 28.349523125 = 226.796185 g
ounces = (pounds × 16) + leftover ounces
kilograms = grams ÷ 1000

Why 28 and 30 both fail

Two rounded factors circulate in recipe books. Using 28 runs about 1.23 percent light, and using 30 runs about 5.82 percent heavy. The second one is the dangerous one, because it is close enough to look deliberate and far enough out to change a dough. On a 16 ounce quantity, 30 adds 26 grams that were never in the recipe.

What your scale can and cannot tell you

A domestic kitchen scale typically resolves to 1 gram, which is about 0.035 ounces, and a jewelry scale resolves to 0.01 grams. Reading a converted figure to more decimals than the instrument supports does not make the measurement better; it only records the arithmetic more precisely than the thing being measured was ever known.

Scales also drift. Most have a tare function and an internal calibration routine, and both are worth using before a batch that depends on ratios, such as bread or pastry. Where a percentage matters more than an absolute figure, weighing everything against the flour rather than converting each ingredient separately removes the conversion from the critical path entirely.

How to use the ounces to grams converter

The reader this page is built for has an American number and a metric scale. A recipe printed in ounces, a bag of coffee sold in ounces, a shipping band written in ounces, a supplement dose on a US label: all of them expect a unit the scale on your counter does not display. One multiplication fixes it, and the multiplier is exact.

Type the ounces and the grams appear as you type. The tool multiplies by 28.349523125, the avoirdupois ounce written out in full. That number is one sixteenth of the pound the 1959 International Yard and Pound Agreement fixed at 0.45359237 kilograms, so there is no measurement anywhere in it and no error to inherit.

Baking is where the conversion earns its keep, because weight is the only honest way to measure flour and American recipes are the last major tradition to publish by volume. An 8 ounce block of cream cheese is 226.80 grams, a 4 ounce stick of butter is 113.40 grams, and a 12 ounce bag of chocolate chips is 340.19 grams.

Fractions are the other quiet source of error. US recipes write quarters and halves rather than decimals, so an entry box needs 0.25 for a quarter ounce and 0.5 for a half. A half ounce is 14.17 grams, close enough to the 15 gram measure sold in metric kitchens that substituting one for the other adds about six percent.

Which ounce does your recipe mean?

The two units share a name and nothing else. An ounce is a unit of mass, one sixteenth of a pound. A fluid ounce is a unit of volume, one sixteenth of a US pint and one one-hundred-and-twenty-eighth of a US gallon, which works out to exactly 29.5735295625 milliliters. Neither one converts into the other without knowing the density of what is being measured.

Water is the only ingredient where the confusion is almost harmless. A US fluid ounce of water weighs about 29.57 grams, which is 1.04 ounces by weight rather than 1.00, so even water is out by four percent. For flour the gap is enormous: a cup of all-purpose flour is 8 fluid ounces of space but only about 4.2 ounces of weight, taking the 120 gram spooned cup King Arthur Baking publishes.

A practical test settles it almost every time. If the ingredient could be poured, the recipe probably means fluid ounces; if it would need a scale or comes in a block, it means weight. When a recipe lists both a cup and an ounce figure for the same ingredient, the ounce figure is nearly always weight, because that is the reason the author bothered to print it.

Shipping weights and net quantity on labels

Postal and courier pricing in the United States is banded in ounces up to a pound and in pounds above that, so anyone shipping from a metric scale has to convert in the direction this page runs. Rounding matters at the edges: the 3.5 ounce ceiling on United States Postal Service letter mail is 99.22 grams, and carriers round up to the next whole band rather than to the nearest one.

Weigh the packed item, not the contents. Padding, tape and the box itself routinely add 20 to 60 grams, which is up to two ounces of headroom you did not budget for, and a band crossed by a single gram costs the same as a band crossed by a hundred.

Consumer packaging runs the same arithmetic in public. NIST Handbook 130, through its Uniform Packaging and Labeling Regulation, requires the net quantity of contents to be declared in both inch-pound and metric units in the United States, which is why a bag reads 12 oz (340 g). The metric figure is rounded for the label, so the true conversion of 12 oz is 340.19 g.

Every ounces value, worked out

29 common ounces figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Questions people ask