How to convert cooking measurements

You’re halfway into a French pastry recipe when it asks for 250g of flour and your measuring cups are in US customary units. You eyeball it, the dough turns into glue, and now you’re angry at the internet. Cooking conversions look simple until you hit the three traps that ruin batches: volume vs weight for dry ingredients, the US/UK/metric cup drift, and oven temperatures that nobody agrees on. This guide covers the unit systems you’ll actually encounter, when precision matters (baking) versus when it doesn’t (soups), the flour-and-sugar weight tables that professional kitchens use, and the temperature conversions that keep your cakes from turning into bricks.

The three cup sizes that trip people up

A “cup” is not one unit. The US customary cup is 240ml, the US legal cup (used on nutrition labels) is 240ml rounded from 236.588ml, the metric cup used in Australia, New Zealand, and Canada is 250ml, and the historical UK imperial cupwas 284ml — though modern UK recipes almost always use grams instead. If a recipe says “1 cup flour” and you use a 250ml cup where a 240ml was intended, you’ve added 4% extra. For bread or macarons that’s enough to wreck the hydration ratio.

Teaspoons and tablespoons

These are more consistent globally. A teaspoon is 5ml everywhere except Australia where it’s sometimes 5ml and sometimes not. A tablespoon is 15ml in the US and UK, 20ml in Australia. That 33% difference in tablespoons matters for anything with salt, leavener, or strong spices — a tablespoon of baking soda when you meant 15ml will taste like soap.

1 tsp  = 5 ml
1 tbsp = 15 ml (US/UK) or 20 ml (AU)
1 fl oz = 29.5735 ml
1 US cup = 16 tbsp = 48 tsp = 240 ml
1 metric cup = 250 ml
1 pint (US) = 473 ml, 1 pint (UK) = 568 ml

Volume vs weight for flour

This is the biggest source of recipe failure. A cup of flour can weigh anywhere from 120g to 155g depending on how it’s scooped. A packed cup (scoop-and-shake) is ~150g. A spooned-and-leveled cup is ~125g. That’s a 20% variance in the core ingredient, which is why every serious baking recipe now lists flour by weight. Use a kitchen scale for baking — a $15 scale pays for itself the first time your cookies stop being a lottery.

Reference weights: all-purpose flour 125g/cup, bread flour 130g/cup, cake flour 115g/cup, whole wheat flour 130g/cup. These assume the spoon-and-level method.

Sugar, butter, and other dense staples

Granulated sugar is denser and more consistent than flour: 200g per US cup. Brown sugar depends on how it’s packed — a packed cup is ~220g, a loose cup is ~170g. Recipes that say “1 cup packed brown sugar” mean push it down with the back of a spoon so it holds the cup shape when dumped. Butter in the US comes in 113g sticks (quarter-pound), subdivided into 8 tablespoons per stick. In Europe, butter is almost always measured in grams.

Liquids are simpler but watch the ounce

Fluid ounces measure volume. Weight ounces measure mass. For water they’re nearly equal (8 fl oz = 236g of water), which is where the confusion comes from. For anything denser — honey, molasses, heavy cream — 8 fl oz weighs more than 8 oz. A recipe that asks for “8 oz honey” is ambiguous; assume weight unless context says volume.

Oven temperatures: Fahrenheit, Celsius, gas marks

The common conversion is C = (F − 32) × 5/9, but memorize these landmarks because they come up constantly: 350°F = 175°C = gas mark 4 (classic baking), 375°F = 190°C = gas mark 5, 400°F = 200°C = gas mark 6, 425°F = 220°C = gas mark 7 (pizza), 450°F = 230°C = gas mark 8.

F     C     Gas  Common use
250   120   1/2  Meringues, slow drying
300   150   2    Slow roasts
350   175   4    Most baking (default)
375   190   5    Muffins, quick breads
400   200   6    Roast vegetables
425   220   7    Pizza, hot-roasting
450   230   8    Bread crust, broiling
500   260   10   Neapolitan pizza (domestic max)

Convection (fan) ovens run hotter. Drop the temperature 15–20°C (~25°F) or reduce the time by 20% when converting from a conventional recipe.

Regional recipe language

American recipes use cups, sticks of butter, and Fahrenheit. British recipes use grams, milliliters, and Celsius — and call self-rising flour what Americans call self-rising flour (same thing, different name). Australian recipes use the 20ml tablespoon. French recipes almost always weight-based, with butter in grams and temperatures in Celsius. When you find a recipe you love, take 10 minutes to write in the conversions next to the original measurements — future-you will thank you.

When precision matters and when it doesn’t

Baking, pastry, and confectionery are chemistry — ratios of flour:fat:liquid:leavener determine whether the thing rises or collapses. Weigh everything. Soups, stews, stir-fries, and braises are forgiving — eyeballed is fine. Candy-making and sugar work require a thermometer, not measuring cups — temperature stages (soft-ball, hard-crack) matter more than weights. Sourdough is weight-obsessed because baker’s percentages define the dough.

Converting a whole recipe

Don’t convert piece by piece — you’ll accumulate rounding errors. Convert the largest ingredient (usually flour or liquid) first, then scale others proportionally. For doubling or halving, rewrite the whole recipe in the target units before you start, and double-check the egg count — you can’t halve an egg without beating and measuring, and 30g of beaten egg is roughly half a large egg.

Common mistakes

Using fl oz and oz interchangeably. Fluid ounces are volume, weight ounces are mass. They’re only equal for water.

Scooping flour instead of spooning. Plunging the cup into the bag packs the flour and adds 20–30g. Spoon into the cup, then level with a knife.

Converting oven temps without adjusting convection. Fan ovens run hot — subtract 20°C from the conventional temperature or your cake browns before it sets.

Assuming 1 cup = 250ml everywhere. In US recipes it’s 240ml. The 4% difference wrecks bread hydration.

Using the wrong tablespoon. Australian tablespoons are 20ml, not 15ml. For salt, baking soda, or baking powder that’s enough to ruin the dish.

Trusting conversions for brown sugar without packing. Packed and loose cups of brown sugar differ by 30%. Recipes almost always mean packed.

Ignoring altitude. Above 3,000ft, leaveners over-rise and liquids evaporate faster. Conversion tables don’t cover this — look up altitude-specific adjustments.

Run the numbers

Convert cups, grams, tablespoons, and oven temperatures in one place with the cooking converter. Pair with the unix timestamp converter for tracking fermentation and proofing start times across timezones, and the time zone converter for coordinating multi-step bakes with collaborators.