Recipe Scaler

What scales and what does not

Multiplying the ingredients is the easy part. The things that catch people out are the ones that do not scale linearly.

Cooking time does not scale

Double a cake and it does not take twice as long. Heat travels from the outside in, so what matters is depth, not total volume. A double batch spread across two tins takes almost exactly the original time; the same batter in one deep tin takes considerably longer and risks a raw middle.

Start checking at the original time and keep going until it tests done.

Temperature does not scale either

Keep it the same. For a noticeably deeper bake, dropping 10–20  °C and extending the time gives the middle a chance to catch up before the outside burns.

Tin size scales by area, not by diameter

This is the one people get wrong most often. Going from a 20 cm to a 23 cm round tin sounds like a small change and is a 32 % increase in area. The tin converter does that arithmetic.

Eggs are the awkward one

You cannot use 1.5 eggs from a shell. Options, in order of preference:

• Adjust the batch to land on a whole number of eggs. A recipe for six when you wanted five is rarely a problem.
• Beat one and weigh half. A large egg is about 50 g out of its shell — roughly 30 g white and 20 g yolk.
• Round up rather than down. Slightly more egg is usually more forgivable than slightly less.

Salt, spices and raising agents need judgement

Salt and strong spices often scale sub-linearly — tripling a recipe and tripling the chilli frequently gives something harsher than intended. Add two-thirds of the scaled amount, taste, and adjust.

Raising agents are the opposite: they should scale properly, because the ratio to flour is what makes the structure work. Too little and it will not rise; too much and it rises then collapses, with a soapy taste.

Pan size and browning

Halving a recipe in the same sized pan spreads it thinner, which means it cooks faster and browns more. For anything fried or roasted, use a smaller pan or the liquid will evaporate too quickly.

Common uses

• Cooking for a different number of people.
• Halving a recipe that makes too much.
• Batch cooking for a freezer.
• Adjusting to the tin you own rather than the one the recipe assumes.

The working, step by step

Questions people ask

Does cooking time scale with the recipe?

No. Heat travels from the outside in, so depth matters more than volume. A double batch in two tins takes about the original time.

What do I do about half an egg?

Beat one and weigh half — a large egg is about 50 g out of the shell. Or adjust the batch to a whole number of eggs.

Should I scale the salt and spices?

Use about two-thirds of the scaled amount, taste, and adjust. Strong flavours often scale sub-linearly.

Should I scale the baking powder?

Yes, properly. The ratio to flour is what creates the structure. Too much makes a bake rise and then collapse.

Do I need a bigger tin?

Scale the area, not the diameter. Going from 20 cm to 23 cm round is a 32 % increase in area.

Worked out in the page

The arithmetic runs in your browser. Nothing you type is sent anywhere, and the site works with no connection once the page has loaded — which is the point when you are in a kitchen with floury hands and a patchy signal.