Metric vs Imperial Cooking: Conversion Guide for Home Cooks
British recipes use grams. American recipes use cups. Your oven thermometer shows Fahrenheit but the recipe says 180°C. Here is a practical guide to navigating metric and imperial in the kitchen — and why this matters more for hosting than everyday cooking.
Why This Matters More When You're Hosting
For an ordinary weeknight dinner, a rough conversion is usually fine. For a dinner party where you've scaled a recipe from 4 to 12 servings and the quantities are precise, conversion errors compound. Getting butter wrong by 20% across a tripled recipe is the difference between a successful tart shell and a crumbly disaster.
The stakes are higher, the quantities are larger, and the time pressure on the night makes stopping to look up conversions even more problematic. Having accurate conversions built into your recipe — rather than scribbled in margins — is part of good hosting preparation.
Weight: Grams and Ounces
Weight is the most reliable measurement in cooking. If a recipe gives weights (as most professional and UK recipes do), use a digital scale — it is faster and more accurate than volume measurements.
- · 1 ounce (oz) = 28.35 grams (g) — use 28 for quick mental maths
- · 100g = approximately 3.5 oz
- · 250g = approximately 9 oz
- · 500g = approximately 1 lb 2 oz
- · 1 kg = 2.2 lbs
Volume: Cups, Tablespoons, and Metric
American recipes use cup measurements extensively — a system that has no equivalent in metric cooking. The core conversions:
- · 1 US cup = 240 ml
- · ½ cup = 120 ml
- · ¼ cup = 60 ml
- · 1 tablespoon (US) = 15 ml
- · 1 teaspoon (US) = 5 ml
- · 1 fluid ounce = 30 ml
Important: cup measurements for dry ingredients (flour, sugar) vary by how packed the cup is. Weight is always more accurate for baking — if an American recipe gives cups for flour, converting to grams before you start will produce more consistent results.
Temperature: Celsius and Fahrenheit
Oven temperature conversion is where errors are most costly — cooking at the wrong temperature for 45 minutes is not recoverable. The key conversions:
- · 150°C = 300°F (low/slow oven)
- · 180°C = 350°F (moderate oven — most baking)
- · 200°C = 400°F (hot oven — roasting)
- · 220°C = 425°F (very hot oven — high-heat roasting)
- · 240°C = 475°F (maximum heat — pizza, bread)
The formula: to convert Celsius to Fahrenheit, multiply by 9/5 and add 32. For a quick approximation: double the Celsius temperature and add 30 (this gives a slightly high result but is within practical range for most oven cooking).
How Morsello Handles This Automatically
Morsello's recipe scaling tool supports both metric and imperial units and displays temperatures in both °C and °F based on your preference settings. When you import a recipe from an American website, the ingredients are shown in their original units, but you can switch to metric display throughout.
This matters especially when scaling for a dinner party: if a recipe originally serves 4 and calls for ½ cup of cream, scaling to 12 servings gives you 1½ cups — which Morsello also displays as 360 ml. No manual conversion required.