Metric to Imperial: The Four Conversions That Matter
“Converting metric to imperial” is not one operation — it is four, and they use different maths. Get them separated in your head and the whole page becomes simple:
- Weight: 1 oz = 28.35 g, 1 lb = 453.6 g
- Volume: 1 US cup = 236.6 mL, 1 US fl oz = 29.57 mL
- Temperature: °F = (°C × 9/5) + 32
- Length (pan sizes): 1 inch = 2.54 cm
Only the first two involve ingredient-dependent judgement. The last two are pure arithmetic, and the temperature one is the only conversion in the kitchen where an error is a food-safety problem rather than a texture problem.
The One-Page Chart
| Metric | Imperial (US) | Common Kitchen Use |
|---|---|---|
| 5 g | 0.18 oz | 1 tsp of salt or baking powder |
| 15 g | 0.53 oz | 1 tbsp of butter |
| 28 g | 1 oz | 2 tbsp of most dry ingredients |
| 57 g | 2 oz | ½ stick of butter |
| 113 g | 4 oz | 1 stick of butter, 1 cup of flour |
| 227 g | 8 oz | 1 cup of butter, 2 cups of sugar |
| 454 g | 1 lb | 4 sticks of butter, ~3¾ cups flour |
| 250 mL | 1.06 cups | 1 metric cup |
| 237 mL | 1 cup | 1 US cup |
| 500 mL | 2.11 cups | 1 US pint |
| 1 L | 4.23 cups | 1 quart + 3½ tbsp |
| 15 cm | 6 in | small round cake tin |
| 20 cm | 8 in | standard round cake tin |
| 23 cm | 9 in | standard round cake tin |
| 30 cm | 12 in | half-sheet pan, 9×13 pan |
Print it, tape it inside a cabinet door. The values are rounded to a usable precision, not to the last decimal — 454 g is the practical 1 lb, and no recipe notices the missing 0.4 g.
The Multiplier Shortcuts
For everyday cooking, three multipliers cover almost everything:
- Ounces to grams: × 28 (or × 30 when you want a fast estimate)
- Grams to ounces: ÷ 28
- Cups to millilitres: × 240 (the US cup rounded up from 236.6)
- Millilitres to cups: ÷ 240
- °C to °F: × 2, then add 30 — accurate to within about 10°F in the 150–220°C baking range
That last shortcut is the one people get wrong most often. 180°C × 2 = 360, + 30 = 390°F. The real answer is 356°F, and 350°F is what most recipes call for. Real-world ovens swing more than 30°F anyway, so the shortcut is fine for setting the dial — but if you are checking a probe thermometer against a recipe’s target internal temperature, use the exact formula. The Oven Temperature Converter does the exact version, along with gas marks and fan-oven adjustments.
Why One Multiplier Never Works for Both Flour and Water
This is the part that trips up metric-to-imperial conversion more than anything else: a cup is a volume, a gram is a weight, and the bridge between them depends entirely on the ingredient.
| Ingredient | 1 US cup | 1 metric cup (250 mL) |
|---|---|---|
| Water | 237 g | 250 g |
| All-purpose flour | 120 g | 127 g |
| Granulated sugar | 200 g | 211 g |
| Brown sugar, packed | 213 g | 225 g |
| Butter, solid | 227 g | 239 g |
| Rolled oats | 90 g | 95 g |
| Honey | 340 g | 358 g |
So when a European recipe says “250 g flour” and you reach for an imperial cup measure, you are not looking for one cup — you are looking for about 2 cups, because flour is light. And a US recipe’s “1 cup of honey” is not 250 g in any system; it is 340 g. The lesson is the same in both directions: convert weight to weight and volume to volume, and only cross the boundary with an ingredient-specific density.
The Kitchen Measurement Converter is built exactly for that crossing, with densities stored for the sixteen ingredients home cooks actually convert.
Converting a Whole Recipe: Do It Once, Not Line by Line
The most common mistake with metric-to-imperial cooking is converting measurements mid-cook. You read “180 g of butter,” convert to 6.35 oz, then convert the ounces to cups, and by the third ingredient you have introduced three rounding errors and lost track of which lines are already converted.
A better workflow:
- Pick one system and commit. If your scale reads grams, convert the whole recipe to grams before you start. If you cook by cups, convert the whole recipe to cups.
- Convert weights with the scale, volumes with the chart. Never convert a weight into a volume unless the recipe is a simple liquid.
- Write it down. Rewrite the ingredient list on a notepad or a card in the target units. Future you will thank present you.
- Convert temperatures last. They are independent of the ingredients, so they can be done at the oven.
- Check the pan. Pan dimensions convert separately, and a 20 cm tin is not the same as an 8-inch tin — it is 20.32 cm, but the two are treated as equivalent because that is how the industries standardised.
If the recipe’s yield needs adjusting at the same time, hand the numbers to the Recipe Servings Calculator and it will rescale every line at once in whichever units you prefer. When a pan substitution is also involved — say an 8-inch US round tin for a 20 cm European one — the Baking Pan Converter confirms whether the batter depth stays the same or whether the bake time needs to move.
The Traps Worth Knowing About
The US fluid ounce versus the imperial fluid ounce. A US fl oz is 29.57 mL; a UK imperial fl oz is 28.41 mL. They differ by 4%, and old British cookbooks use the imperial one. A pint is worse: 473 mL in the US, 568 mL in the UK. If a recipe from a 1970s British book calls for a pint of stock, use 568 mL.
Cups are not 250 mL everywhere. US and Japanese cups are ~237 mL (the Japanese one is exactly 200 mL for rice). Australian, Canadian, and New Zealand cups are 250 mL. A recipe using 4 cups is therefore anywhere between 800 mL and 1 L.
Ounce confusion is twofold — weight or volume. “8 oz of cheese” is a weight (227 g); “8 fl oz of milk” is a volume (237 mL). Recipes that skip the “fl” are usually talking about weight, but not always, and that is exactly why the gram column matters.
Spoons differ too. A US tablespoon is 14.79 mL, a British metric tablespoon is 15 mL, and an Australian tablespoon is 20 mL. In a small batch of vinaigrette, that is a measurable difference in acidity.
If any of those traps describe a recipe you are about to cook, the Conversion Chart lists the equivalences in both directions for every unit mentioned above, and it is organised by ingredient rather than by unit, which is the order you actually need them in while cooking.
Try Our Free Tools
Stop converting by hand. The Kitchen Measurement Converter translates grams, ounces, cups, millilitres, tablespoons, and fluid ounces in both directions for sixteen ingredients. The Oven Temperature Converter handles °F, °C, gas marks, and fan ovens, and the Conversion Chart is a printable reference for the whole list. Free, no signup, instant.