Cooking Converter

How this is worked out

Volume to weight is density × volume, and density is a property of the ingredient — not of the cup:

grams = millilitres × density

A US cup is 236.588 ml. Fill it with plain flour (density about 0.53 g/ml) and you have 125 g. Fill the same cup with honey (1.42 g/ml) and you have 336 g. They are not close, and no single conversion factor can serve both — which is why this tool asks what you are measuring and refuses to answer for an ingredient it has no density for, rather than quietly applying water's.

The second problem is the scoop. Flour compresses. Spooned gently into a cup it might weigh 100 g; scooped and packed it can reach 150 g. That is a fifty per cent spread on the same nominal measure, and it is the single biggest reason a baking recipe fails for one person and works for another. The calculator shows that range rather than a single confident number.

Oven temperatures convert with the standard Celsius-Fahrenheit formula, and gas marks are a fixed lookup. A fan or convection oven runs hotter than the dial implies — the conventional adjustment is 20 °C lower than a recipe written for a conventional oven.

A worked example

Why bakers weigh and cooks do not have to

A stew tolerates being twenty per cent out on the carrots. A cake does not tolerate being twenty per cent out on the flour, because baking is a set of ratios — flour to fat to sugar to liquid to raising agent — and changing one of them changes the structure rather than the seasoning.

That is the whole distinction. Savoury cooking is forgiving and volume measures are fine. Baking is chemistry with a tolerance, and the tolerance is smaller than the error a cup of flour introduces. A kitchen scale costs very little and removes the problem entirely.

If you are following a volume-based recipe and cannot weigh, the best available technique is to spoon flour lightly into the cup and level it with a knife rather than scooping with the cup itself. That gets you toward the low end of the range consistently, which at least makes your results repeatable.

A cup is three different sizes

A US cup is 236.6 ml. A metric cup, used in Australia and much of Europe, is 250 ml. An old imperial cup is 284 ml. A recipe that says "1 cup" without saying which is ambiguous by up to twenty per cent before you have even considered what is in it.

In practice, American recipes mean the US cup, Australian recipes mean 250 ml, and British recipes mostly avoid cups entirely and give weights — which is one reason British baking recipes travel better than American ones.

The Australian tablespoon is a separate trap: it is 20 ml, where almost everywhere else it is 15 ml. On a recipe using four tablespoons of something potent, that is a third more than intended.

Fan ovens, and why things burn on the outside

A fan oven circulates air, which transfers heat to food far more efficiently than still air at the same temperature. The result is that a fan oven at 180 °C cooks roughly like a conventional oven at 200 °C, so a recipe written for a conventional oven and followed literally in a fan oven overcooks.

The conventional correction is 20 °C, and it is worth applying by default unless a recipe explicitly says "fan". Some manufacturers suggest reducing the time instead, which works for thin items and not for anything that needs to cook through — a cake at too high a temperature sets its crust before the middle has risen.

Oven thermostats are also frequently inaccurate by 10–20 °C in either direction, and they drift with age. An oven thermometer is the cheapest way to find out whether your oven is telling the truth, and it explains a surprising number of recipe failures.

Scaling a recipe, and what does not scale

Ingredients scale linearly and the calculator handles that. Several other things do not, and this is where doubled recipes go wrong.

Cooking time does not scale with quantity — it scales with thickness. A cake mixture doubled into the same size tin takes far longer than twice as long and will likely burn outside before setting inside; the right move is two tins, not one deeper one. A doubled stew in a wider pan may take barely longer at all.

Salt and strong spices often want slightly less than a straight doubling, and raising agents in baking are the one thing to scale exactly — halving a cake recipe and rounding the baking powder up is a reliable way to produce something that rises and then collapses.

Assumptions and sources

Densities

Grams per millilitre for each ingredient as normally scooped. Where an ingredient compresses, the scoop variance is stated alongside.

Cup sizes

US cup 236.5882365 ml, metric cup 250 ml, imperial cup 284.130625 ml. US tablespoon 14.787 ml; metric 15 ml; Australian 20 ml.

Oven temperatures

Standard Celsius–Fahrenheit conversion with the conventional gas mark lookup. Fan adjustment of 20 °C is the usual manufacturer guidance.

Not modelled

Altitude, which meaningfully changes baking above roughly 1,000 m, and humidity, which changes how much liquid flour absorbs.