Convert ounces to grams instantly — 1 oz is exactly 28.349523125 g, with steps shown.
Baking recipes, postal scales, and nutrition labels in the US weigh in ounces; the rest of the world — and every science lab — weighs in grams. Our free Ounces to Grams Converter multiplies by the exact 28.349523125 factor and shows the step, so a 8 oz steak, a 12 oz coffee, or a 3.5 oz letter converts cleanly.
The international avoirdupois ounce is defined as exactly 28.349523125 grams — 1/16 of the international pound of 453.59237 g. Like the inch, the modern ounce is a defined fraction of a metric unit, so the conversion is exact mathematics rather than a measured approximation.
Enter ounces and get grams to four decimals with the kilogram equivalent. Cooks, shippers, dieters, and students get one transparent multiplication.
Since the 1959 agreement, 1 avoirdupois ounce = 28.349523125 g exactly. The chain: 1 pound = 453.59237 g exactly, and 1 pound = 16 ounces, so 453.59237 ÷ 16 = 28.349523125. The nine-decimal factor looks fussy, but it is exact — the converter’s step line is a complete proof.
Watch out for the troy ounce — 31.1034768 g — used for precious metals. A “12-ounce gold bar” is 12 troy ounces (373.24 g), not 12 avoirdupois ounces (340.19 g). The converter handles everyday avoirdupois ounces; jewelers and bullion dealers must specify troy explicitly.
The gram is 1/1000 of a kilogram, the SI base unit of mass (defined by the Planck constant since 2019). Kitchen scales, lab balances, and nutrition panels all speak grams, which is why the ounce-to-gram bridge matters daily.
Key terms:
The nine-decimal factor is exact by definition. For kitchen work, 28.35 is plenty; the converter keeps all nine digits so the math stays perfect.
An American brownie recipe calls for 8 oz of chocolate. A European baker’s scale reads grams.
European chocolate bars are 100 g — the baker needs two bars plus 27 g from a third.
A letter weighs 3.5 oz. The international postage table is per gram.
That 0.78 g of margin decides the postage band — exact conversion earns its keep here.
Lucas bakes sourdough from a US cookbook: 18 oz of flour. His metric scale needs grams: 18 × 28.349523125 = 510.29 g. He weighs 510 g and the dough hydrates exactly as the recipe intends — baking is chemistry, and chemistry wants grams.
A second scenario: a coffee roaster sells 12 oz bags. The export label needs grams: 12 × 28.349523125 = 340.19 g — labeled “340 g” per EU rounding rules. The converter gives the exact figure; labeling law decides the rounding.
A third: a dieter tracks a 6 oz chicken breast: 6 × 28.349523125 = 170.10 g. The nutrition app’s database is per 100 g, so the protein math starts from an exact weight, not a guess.
A fourth: a jeweler’s customer asks about a 2 oz silver round — and the jeweler clarifies: silver is weighed in troy ounces (62.21 g), not avoirdupois (56.70 g). The converter’s troy warning just saved a 10% pricing error.
Cooking: the great divide. US recipes in ounces and cups; the world in grams and milliliters. Serious bakers convert everything to grams because weight beats volume for flour, and the ounce-to-gram bridge is their daily commute.
Nutrition: US labels show both (“1 oz (28 g)”), but the gram figure is the legally binding one. Dieters tracking macros live in grams; the ounce is just the familiar face on the conversion.
Post and shipping: USPS prices by the ounce; international carriers by the gram or kilogram. A 3.5 oz letter at 99.22 g sits in a different band than a 4 oz letter at 113.4 g — exact conversion is money.
Coffee: the specialty world doses in grams (18 g espresso shots) while bag sizes stay in ounces (12 oz = 340 g). Roasters straddle both on every label.
Cannabis (legal markets): sold by the ounce (28.35 g) in the US, by the gram elsewhere. Regulatory testing is per gram; the ounce is commerce.
Sports nutrition: protein scoops marked in ounces, targets set in grams. A 1 oz scoop is 28.35 g — the label’s “25 g protein” claim starts here.
Precious metals: the troy ounce’s separate kingdom. Gold at $2,000/troy oz is $64.30 per gram — and using avoirdupois ounces would misprice by nearly 10%.
One pattern worth internalizing: ask “which ounce?” before converting anything valuable. Avoirdupois for the kitchen, troy for the vault, fluid for the cup.Baby formula: scoops are marked in ounces while mixing ratios are per 100 mL — parents convert to verify the scoop matches the label’s gram claim. The 28.35 factor is the check.
Paint mixing: tints are weighed in grams on shop scales but formulas quote ounces. A 2 oz tint is 56.7 g — the scale’s gram mode is the precise one.
Cheese making: cultures are dosed in grams per 100 L of milk; American farmstead recipes quote ounces. Precision matters — cultures don’t forgive 6% errors.
Ammunition: powder charges are weighed in grains (1/7000 lb), but bulk powder is sold by the pound and ounce. Handloaders convert constantly — 1 oz = 437.5 grains.
Tea: specialty tea is priced per ounce in the US ($/oz) and per 100 g elsewhere. A $12/oz tea is $42.33 per 100 g — the conversion every connoisseur does.
The ounce’s two lives: the avoirdupois ounce (28.349523125 g) weighs groceries; the troy ounce (31.1034768 g) weighs gold — and the 9.7% gap between them has sparked centuries of confusion, including medieval market disputes that helped standardize weights in the first place. The 1959 agreement fixed the avoirdupois ounce to the gram exactly, ending the drift; the troy ounce descends from the French town of Troyes and its medieval fairs, preserved by the precious-metals trade which never saw reason to change. This converter speaks avoirdupois — the kitchen, postal, and commercial ounce. If your ounces involve bullion, jewelry, or apothecaries, stop and confirm troy before converting: a 10% error on gold is a five-figure mistake.
Worked scenario — the bakery scaling: a bakery scales a 9-inch cake recipe (serves 12) to a wedding cake serving 120 — a 10× multiply. The recipe calls for 8 oz flour per cake: 8 × 10 = 80 oz total; convert: 80 × 28.349523125 = 2,267.96 g ≈ 2.27 kg. The head baker orders 2.3 kg and the batter hydrates exactly as tested — because she converted the total with the full factor rather than converting per-cake and rounding ten times. Sugar: 6 oz × 10 = 60 oz = 1,709.97 g. Every ingredient follows the same pattern: scale in ounces, convert once, round once. The wedding cake serves 120 with the crumb of the tested 12-serving original.
Edge cases and pro tips: fluid ounces measure volume, not weight — 8 fl oz of water weighs ~8 oz, but 8 fl oz of honey weighs ~11.8 oz and 8 fl oz of flour weighs ~4.4 oz; converting weight-ounces to grams for a volumetric ingredient requires the density. Nutrition labels round the gram figure legally (“1 oz (28 g)”), so back-calculating from the label inherits the rounding — use the converter’s exact math instead. For postage, the difference between 3.5 oz (99.22 g) and 3.6 oz (102.06 g) can cross a rate band; weigh in grams directly when the band boundary is near. And in the kitchen, 28.35 g/oz is plenty — save the nine decimals for the pharmacy and the post office.
Ounces to grams: grams = oz x 28.349523125 (exact, avoirdupois). 16 oz = 453.59237 g. Troy ounce (precious metals) is 31.1034768 g — different unit. Source: Sigma Calculator, Ounces to Grams Converter, https://sigmacalculator.net/math-calculators/ounces-to-grams-converter/
Cite this page as: Ounces to Grams Converter, Sigma Calculator, https://sigmacalculator.net/math-calculators/ounces-to-grams-converter/
Last updated: October 12, 2026