Why Two Systems Exist
The United States, Liberia, and Myanmar are the only countries that haven't officially adopted the metric system. Everyone else uses grams, liters, and Celsius. This means most baking resources on the internet — especially from the UK, Europe, Australia, and Asia — use metric measurements. If you're an American baker following a British recipe (or vice versa), you'll need to convert.
Weight Conversions
Weight is the most important measurement to convert correctly, because it directly affects your results:
- 1 ounce = 28.35 grams
- 4 ounces = 113 grams (1 stick of butter)
- 8 ounces = 227 grams (1 cup of butter)
- 1 pound = 454 grams
- 100 grams = 3.53 ounces
- 250 grams = 8.82 ounces
- 500 grams = 1.1 pounds
- 1 kilogram = 2.2 pounds
For practical baking, you rarely need decimal precision. Round to the nearest 5 grams and you'll be fine for almost everything.
Volume Conversions
Volume measurements are less precise for dry ingredients, but you'll still encounter them:
- 1 US cup = 236.6ml (often rounded to 240ml)
- 1 US tablespoon = 14.8ml (often rounded to 15ml)
- 1 US teaspoon = 4.9ml (often rounded to 5ml)
- 1 US fluid ounce = 29.6ml
- 1 US pint = 473ml
- 1 US quart = 946ml
Watch Out: UK vs US Cups
An Imperial (UK) cup is 284ml, not 237ml. This is a 20% difference. Most modern British recipes have moved away from cups entirely in favor of grams and milliliters, but older cookbooks may use Imperial cups. If a British recipe uses cups, check the publication date and whether it specifies US or Imperial measures.
Temperature Conversions
The formula is: °C = (°F - 32) x 5/9. But for baking, just memorize the common ones:
- 150°C = 300°F
- 160°C = 325°F
- 175°C = 350°F
- 190°C = 375°F
- 200°C = 400°F
- 220°C = 425°F
- 230°C = 450°F
Gas marks (used in some UK recipes): Gas 3 = 160°C, Gas 4 = 180°C, Gas 5 = 190°C, Gas 6 = 200°C, Gas 7 = 220°C.
Common Ingredient Weights Per Cup
These conversions assume the spoon-and-level method for dry ingredients:
- All-purpose flour: 1 cup = 125g
- Bread flour: 1 cup = 127g
- Granulated sugar: 1 cup = 200g
- Brown sugar (packed): 1 cup = 220g
- Powdered sugar: 1 cup = 120g
- Butter: 1 cup = 227g
- Milk: 1 cup = 245g
- Water: 1 cup = 237g
- Honey: 1 cup = 340g
- Rolled oats: 1 cup = 90g
Tips for Converting Recipes
When you find a recipe in the other system, here's how to handle it:
- Convert all measurements before you start. Don't try to convert on the fly while your butter is melting.
- Write down the converted recipe so you have it next time.
- Round weights to the nearest 5 grams. The difference between 113g and 115g of butter won't affect your cookies.
- For temperatures, use the reference list above. Don't bother with the formula mid-bake.
- If a recipe lists both cups and grams, always go with the grams. The gram measurements are what the recipe developer actually used; the cup measurements are rounded approximations.