Cooking Conversions: Metric Recipes for Imperial Kitchens

By UnitConvert · August 10, 2026 · 6 min read

The kitchen is where the metric-imperial divide gets personal. A Paris cookbook calls for 200 grams of flour; a New York blog calls for 1½ cups. The two measure the same ingredient in different units, and converting between them is not a single multiplication — it depends on what you are measuring and whether the recipe used weight or volume. This article covers the conversions a cook needs, and the one principle that makes them accurate: weigh, don't scoop.

Weight vs Volume in Cooking

Cooking measures ingredients two ways: by weight (grams, ounces) and by volume (cups, tablespoons, milliliters). The two are not interchangeable without knowing the ingredient's density, and this is the source of most kitchen conversion errors. A cup of flour and a cup of sugar weigh very different amounts — about 120 g for all-purpose flour, about 200 g for granulated sugar — because flour is fluffy and sugar is dense. A "cup" is a unit of volume, not of mass.

Professional bakers almost always weigh. A kitchen scale reads grams to the nearest gram, and 200 g of flour is 200 g regardless of how tightly it was scooped. A measuring cup, by contrast, can vary by 20% or more depending on whether the flour was spooned or dipped, sifted or not. For savory cooking where ratios are forgiving, the difference rarely matters; for baking, where chemistry drives the result, it is the difference between a good loaf and a failed one.

Common Conversions: Grams, Ounces, Cups, and Milliliters

The core weight conversion is simple: 1 ounce = 28.3495 g, and 1 pound = 453.592 g. For volume, 1 US cup = 236.588 ml (often rounded to 240 ml), 1 US tablespoon = 14.787 ml (rounded to 15 ml), and 1 US teaspoon = 4.929 ml (rounded to 5 ml). These are exact definitions; the rounding introduces a small error acceptable in cooking but not in baking at scale.

The harder conversions cross between weight and volume, because they depend on the ingredient:

• All-purpose flour: 1 cup ≈ 120 g (spooned and leveled); 1 oz ≈ 28 g.
• Granulated sugar: 1 cup ≈ 200 g; 1 oz ≈ 28 g.
• Brown sugar (packed): 1 cup ≈ 220 g.
• Butter: 1 cup ≈ 227 g; 1 stick = 4 oz = 113 g.
• Water and milk: 1 cup ≈ 240 g (water's density makes 1 ml ≈ 1 g, so volume and weight nearly coincide).
• Honey and syrups: 1 cup ≈ 340 g (dense — about 40% heavier than water by volume).

These are approximations, not exact — flour varies by brand and humidity, sugar by crystal size — but they are close enough to adapt a recipe. The safest approach is to find a source that gives weights and convert the volume equivalents from those weights, rather than relying on a generic "1 cup = X grams" table that ignores the ingredient.

Why Weight Is More Accurate Than Volume for Baking

Baking is chemistry with a timer. The ratio of flour to water to leavening to fat determines the structure and texture of the finished bake, and a 10% error in flour — easily produced by scooping directly from the bag, which packs the flour — is enough to turn a tender cake dry or a risen loaf flat. Volume measurement makes that error invisible: two cooks can measure "1 cup of flour" and hold 120 g and 150 g respectively, with no way to tell from the cup which is which.

Weight measurement removes the ambiguity. A scale that reads 120 g delivers 120 g of flour, packed or not, humid or dry, sifted or spooned. This is why professional recipes, serious baking books, and most non-US cookbooks give ingredients in grams. If you bake regularly and have not yet bought a kitchen scale, the roughly twenty dollars it costs is the single highest-leverage investment you can make in your results. Once you weigh, you stop converting cups to grams — you just use the grams.

Oven Temperature: Celsius to Fahrenheit

Oven temperatures are a special case of temperature conversion because they are quoted in round numbers in each system, and a direct conversion gives an awkward number. A recipe that says "180°C" converts to 356°F, but no US oven has a 356°F setting — the nearest standard mark is 350°F. So cooks round to the nearest common oven setting rather than converting exactly:

• 120°C ≈ 250°F (slow, for drying or meringues)
• 150°C ≈ 300°F (low, for slow baking)
• 180°C ≈ 350°F (moderate, the most common baking temperature)
• 200°C ≈ 400°F (hot, for roasts and bread)
• 220°C ≈ 425°F (hotter, for initial crust)
• 230°C ≈ 450°F (very hot, for pizza and high-heat roasting)
• 260°C ≈ 500°F (maximum, for broiling and fast pizza)

The exact formula is °F = °C × 9/5 + 32, covered in our temperature conversion article, but in the kitchen the rounded table is what you want. Ovens cycle around their set point by 10–25°F anyway, so the few degrees lost in rounding are within the oven's own variation.

Adapting International Recipes

The practical workflow for adapting a recipe from one system to the other:

1. Convert weights first. If the recipe gives grams and you think in ounces, divide by 28.35; if it gives ounces and you think in grams, multiply by 28.35. For pound-based recipes, multiply by 453.6 to get grams.
2. Convert liquid volumes. Multiply milliliters by 0.0338 to get fluid ounces, or divide fluid ounces by 0.0338 to get milliliters. For cups, use 1 cup = 240 ml as a working conversion.
3. Convert oven temperature. Use the rounded table above, not the exact formula, because ovens have stepped settings.
4. Convert pan sizes by area, not diameter. A 20 cm round pan has area π × 10² ≈ 314 cm²; an 8-inch round pan has π × 4² ≈ 50 in² ≈ 323 cm² — close enough to substitute. A 23 cm round pan is not the same as a 23 cm square pan — the square has about 27% more area. Match by area, not by one dimension.
5. Adjust for altitude separately. High-altitude changes (lower boiling point, faster leavening) are not a unit conversion — they are a recipe change. Convert the units first, then apply altitude corrections to the converted recipe.

One trap: do not convert a recipe twice. If a French recipe gives 200 g of flour and you convert it to 1⅔ cups for an American audience, do not let someone convert those cups back to grams using a generic table — the round-trip will not give 200 g. Keep the original weight as the source of truth, and treat the volume as an approximation for readers without a scale.

Summary

Cooking conversion is mostly about crossing between weight and volume, and the key fact is that the two are not interchangeable without knowing the ingredient. A cup of flour weighs about 120 g; a cup of sugar about 200 g; a cup of water about 240 g — the same volume holds different masses because density varies. Weight is more accurate than volume, especially for baking, because a scale removes the packing and settling error a cup introduces. Oven temperatures convert with °F = °C × 9/5 + 32, but in practice cooks round to the nearest standard oven setting (180°C ≈ 350°F) because ovens cycle well beyond the rounding error. Adapting international recipes means converting weights, then volumes, then oven temperature, then pan size by area — and keeping the original weight as the source of truth so the recipe does not drift on a round-trip. The single best upgrade most home cooks can make is a kitchen scale: it eliminates most of these conversions by making them unnecessary.