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Metric vs. US Customary: Converting Recipes Between Systems
How to convert recipes between grams and cups in both directions, which unit differences actually matter, and why weight-based recipes travel better.
Por Ali RazaAtualizado em 7 min de leitura
Most of the world bakes by weight. The United States bakes by volume. If you cook from recipes on both sides of that divide, you are translating constantly — and the translation is not symmetrical.
Why the two systems developed differently
It is largely a question of when home scales became cheap. European home baking standardised around the kitchen scale early; American home baking standardised around nested measuring cups, which were cheaper and needed no calibration. Both work, but volume measurement carries a variability that weight does not.
This is why professional and modern recipe development, including in the US, has moved steadily toward weights.
Converting metric to US: the harder direction
Going from grams to cups requires knowing the ingredient's density, so there is no single conversion factor. You need a per-ingredient value.
| Ingredient | 1 cup = | 100 g = | 250 g = |
|---|---|---|---|
| Granulated sugar | 200 g | ½ cup | 1¼ cups |
| All-purpose flour | 120 g | ⅚ cup | 2 cups + 1 tbsp |
| Butter | 227 g | 7 tbsp | 1 cup + 2 tbsp |
| Powdered sugar | 120 g | ⅚ cup | 2 cups + 1 tbsp |
| Cocoa powder | 85 g | 1⅕ cups | 2⅘ cups |
| Milk | 245 g | 0.41 cup | 1 cup |
| Water | 236.6 g | 0.42 cup | 1 cup + 1 tbsp |
Notice how rarely the answers are clean. This is the fundamental awkwardness of metric-to-volume conversion, and the reason it is worth just buying a scale if you regularly cook from European recipes.
Converting US to metric: the easier direction
This direction is more pleasant, because you are multiplying a fraction by a round number rather than dividing an awkward number.
| Cups | Sugar | Flour | Butter |
|---|---|---|---|
| ¼ cup | 50 g | 30 g | 57 g |
| ⅓ cup | 67 g | 40 g | 76 g |
| ½ cup | 100 g | 60 g | 113 g |
| ⅔ cup | 133 g | 80 g | 151 g |
| ¾ cup | 150 g | 90 g | 170 g |
| 1 cup | 200 g | 120 g | 227 g |
| 1½ cups | 300 g | 180 g | 340 g |
| 2 cups | 400 g | 240 g | 454 g |
The volume differences that matter
| Unit | US | Metric / Europe | Australia |
|---|---|---|---|
| Cup | 236.6 ml | 250 ml | 250 ml |
| Tablespoon | 14.79 ml | 15 ml | 20 ml |
| Teaspoon | 4.93 ml | 5 ml | 5 ml |
- Teaspoons are effectively identical everywhere — ignore the difference.
- Tablespoons are identical except in Australia, where they are 35% larger.
- Cups differ by 5.7%, which matters at volume: four US cups is 946 ml, four metric cups is 1,000 ml.
Temperature, which trips up as many recipes
| Fahrenheit | Celsius | Fan / convection | Gas mark |
|---|---|---|---|
| 300°F | 150°C | 130°C | 2 |
| 325°F | 165°C | 145°C | 3 |
| 350°F | 175°C | 160°C | 4 |
| 375°F | 190°C | 170°C | 5 |
| 400°F | 200°C | 180°C | 6 |
| 425°F | 220°C | 200°C | 7 |
| 450°F | 230°C | 210°C | 8 |
Fan ovens run hotter at the same setting because moving air transfers heat faster. Reduce by about 20°C from the conventional figure, and start checking earlier than the recipe says.
Tin sizes, the last trap
A 9-inch round tin is 23 cm; an 8-inch is 20 cm. These sound close and are not — a 9-inch tin has 27% more area than an 8-inch, so the same batter bakes shallower and faster. If you substitute, adjust the time and start checking well before the stated minimum.
The genuinely good news
Once converted, write the metric figures directly onto your copy of the recipe. Do it once and you never do it again — and a weight-based version of a recipe is more reproducible than the volume-based original ever was.