Ingredient scale calculator
Ingredients scale; cooking does not. Doubling a cake batter does not double the baking time; it adds perhaps a third, and the tin size matters more than the clock. Doubling a stew barely changes the simmer. Salt and strong spices often want slightly less than the factor suggests, and yeast in a large batch works faster because the dough holds its own heat. Scale the quantities here, then use judgement on the method.
The scaling factor is target servings divided by original servings. Going from 4 to 6 is a factor of 1.5, so 250 g becomes 375 g. Every ingredient takes the same multiplication; almost nothing about the method does.
How to scale a recipe
Ingredients scale by multiplication because they are quantities. Cooking does not, because it is governed by geometry and by heat, and neither of those grows the way a shopping list does. A pan holds volume and browns across an area, and doubling the contents of one pan doubles the volume while leaving the area exactly where it was. Food that used to sear now releases more water than the same surface can drive off, the pan cools, and what should have browned steams instead. The fix is a second pan or a bigger one, never a longer time.
Baking is the same problem measured vertically. Heat reaches the middle of a cake by conduction from the outside, and the time that takes grows with the square of the distance rather than in proportion to it. Double a batter into the same tin and you have not made a cake that needs twice as long; you have made one twice as deep, whose centre is four times as far away in thermal terms, and whose edges will be dry before the middle sets. Two tins keeps the depth and therefore keeps roughly the original bake time. If you must go up a tin size, note that area grows with the square of the diameter too: a 20 cm round tin is 314 cm² and a 23 cm is 415, which is 1.32 times, not the 1.5 you were after. You would need about 24.5 cm for that.
A few ingredients have their own reasons for not scaling. Chemical leavening tracks the flour and behaves. Yeast does not, because a larger mass of dough holds its own fermentation heat and works faster than a small one at the same room temperature, so watch the dough rather than the clock. A sauce being reduced evaporates from its surface, so twice the sauce in the same pan takes roughly twice as long to reduce rather than the same time. And eggs are simply discrete: beat one, weigh it, and use the fraction you need, remembering that a US large egg is about 50 g out of the shell while a European large is nearer 55.
What people use it for
- Cooking for more people than a recipe was written for
- Halving a recipe down to two portions
- Working out whether a batch fits the tin you own
- Converting a recipe to a different tin size without guessing
- Batch cooking for the freezer
- Scaling a bread formula to the flour you have left
Questions
Multiply every ingredient by two, then leave the method alone until you have thought about the pan. Cooking time rises far less than the quantity does, and the vessel usually has to change.
No, and it fails in a specific way. A doubled cake split across two tins bakes in roughly the original time. Poured into one deep tin it may need half as long again and will still be uneven, because heat has twice as far to travel to the middle.
By area, not by diameter. A 20 cm round tin is 314 cm² and a 23 cm one is 415, so stepping up a size gives you a third more capacity rather than a half. For 1.5 times the batter you want about 24.5 cm.
Scale a little short of the factor for salt and anything strongly flavoured, then taste and correct at the end. Adding is easy and removing is not.
The weight does; the timing does not. A larger dough retains its own heat and ferments faster than a small one in the same kitchen, so judge by how the dough looks and feels rather than by the recipe’s clock.
The awkward one, because they come in whole units. Beat an egg thoroughly and weigh out the share you need. A US large egg is about 50 g without its shell and a European large egg nearer 55, which matters if you are following an American recipe closely.
They reduce at the same rate per unit of surface, so a doubled sauce in the same pan takes about twice as long. A wider pan reduces faster than a longer wait does.
Several. Anything that needs a minimum depth to work, such as a caramel deep enough to read a thermometer in, or a braise where the liquid has to cover the meat. Below a certain size the method stops being the same method.