Ounces vs Grams Explained
Ounces and grams measure small masses; one avoirdupois ounce equals 28.3495 grams.
Quick answer
1 US customary ounce (avoirdupois) = 28.3495 grams. 1 gram ≈ 0.03527 oz. Sixteen ounces make one pound. Fluid ounces measure volume, not mass—do not swap fl oz for weight oz without density. Multiply oz by 28.35 for grams.
Overview
Recipe globalization made grams-on-a-scale the precision standard for baking while US home cooks still meet cups and ounces in legacy cookbooks. Weight ounces (oz) differ from fluid ounces (fl oz)—only weight ounces convert to grams directly without knowing ingredient density. Nutrition labels in the US list serving size in grams alongside oz for compliance. Small package shipping, coffee dosing, and supplement capsules frequently bounce between 28 g and 1 oz nominal sizes that are close but not identical for strict tracking.
Avoirdupois ounce vs troy ounce
Kitchen and postal ounces use avoirdupois: 28.3495 g per oz. Troy ounce for precious metals is heavier: ~31.103 g. Jewelry contexts require troy; flour does not.
Always confirm ounce type in financial or specialty domains before converting to grams for inventory valuation.
Cooking and baking precision
Professional baking formulas in grams scale linearly; volume cups do not. Converting 8 oz butter (by weight) to 227 g matches stick labeling better than water cup volume.
Coffee specialty recipes quote 18 g dose vs 0.63 oz—same shot, different unit habit. Use scale tare in one unit consistently.
Weight ounce vs fluid ounce
US fluid ounce (volume) ≈ 29.57 mL for water-like density only. Eight fl oz water ≈ 236 g, but 8 fl oz honey weighs more grams—volume-to-mass needs density.
Recipe saying 6 oz chocolate chips usually means weight; 6 fl oz milk means volume. Context and ingredient type disambiguate.
Relating to pounds and kilograms
16 oz = 1 lb ≈ 453.592 g. 1 kg ≈ 35.274 oz. Bulk meat or produce priced per lb converts to per-kg by dividing lb price by 0.4536 kg equivalent.
Nutrition panels show 28 g serving ≈ 1 oz reference for snack comparison across US and EU packaging.
Practical conversion habits
Memorize anchors: 1 oz ≈ 28 g, 4 oz ≈ 113 g, 8 oz ≈ 227 g. For spices under 10 g, gram precision beats 0.3 oz rounding on cheap scales.
Import recipes by converting entire ingredient list to grams once, save scaled template, cook from grams thereafter to reduce repeated conversion error.
Examples
Chocolate bar 3.5 oz
3.5 × 28.35 ≈ 99.2 g—EU label may round 100 g; check net weight statement.
Espresso dose 18 g
18 ÷ 28.35 ≈ 0.63 oz—communicate with US roasters using oz nomenclature.
Common mistakes and edge cases
- Treating fluid ounces as weight ounces in baking.
- Using troy ounce factor for food.
- Rounding 28.35 to 30 g repeatedly across many ingredients, skewing totals.
- Converting volume cups to grams without ingredient-specific density.
Related resources
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Last reviewed: 2026-05-23