Custard Ratio Calculator

A typical home pouring-custard ratio is about 3 whole eggs per 600ml of milk, with 2-3 tablespoons of caster sugar and a teaspoon of vanilla extract — this gives a smooth, pourable custard with good body. There is no single official ratio: richer recipes use yolks rather than whole eggs (Delia Smith's "Proper Custard" uses 6 egg yolks per 570ml of cream, and BBC Good Food uses 4 yolks across roughly 900ml of milk and cream). Switching from whole eggs to yolks changes the count because yolks alone are the thickening, enriching part. Whichever ratio you start from, custard scales linearly — double the dairy, double the eggs and sugar.

Whole eggs give a lighter custard that sets firmer — good for baked custards and custard tarts. Egg yolks alone produce a richer, silkier, more golden custard — perfect for creme anglaise and pouring custard. For a balanced approach, use a mix: 2 whole eggs plus 2 extra yolks per 600ml for the best of both worlds.

Curdling happens when the eggs get too hot too quickly. To prevent this: temper the eggs by gradually adding hot milk to them while whisking (not the other way round), cook on a gentle heat stirring constantly, and never let it boil. If cooking on the hob, the custard is ready when it coats the back of a wooden spoon and a line drawn through it holds. Remove from heat immediately.

Yes, replacing some or all of the milk with single or double cream makes a richer custard. A common ratio for creme anglaise is 300ml milk and 300ml double cream with 6 egg yolks. For a baked custard, half-and-half milk and single cream works well. Pure cream custard is very rich and is typically reserved for creme brulee.

Traditional custard thickens from the egg proteins coagulating when heated gently. More eggs will give a thicker custard. If you prefer using cornflour for reliability, add 1 tablespoon per 600ml of milk — this creates a more stable custard that is less likely to curdle and is closer to a creme patissiere in consistency.