Latte Milk Steaming Calculator
Work out how much cold milk to start with for a latte, cappuccino or flat white so the steamed, foamed volume fills your cup.
How it works
Milk volume = drink − espresso · Cold milk = milk volume ÷ (1 + expansion) · Foam = milk volume − cold milk
Steaming stretches milk by whipping air into it, so the frothed volume is larger than the cold milk you poured in. To fill a cup exactly you work backward: subtract the espresso from the drink size to get the finished milk volume, then divide by one plus the expansion factor for the style. A flat white uses thin microfoam (about 15% growth), a latte a bit more (about 30%), and a cappuccino a thick, airy foam (roughly 60%).
Worked example
For a 350 ml latte with a 60 ml double shot, the milk should end up at 350 − 60 = 290 ml. At 30% expansion you start with 290 ÷ 1.30 ≈ 223 ml of cold milk, which whips up to about 67 ml of foam.
Frequently asked questions
How much milk for a latte vs a cappuccino?
Both start from the finished milk volume, but a cappuccino incorporates much more air. For the same cup you pour slightly less cold milk for a cappuccino because it expands more into foam — roughly 60% growth versus about 30% for a latte.
Why start with less milk than the cup holds?
Because steaming adds air and volume. If you filled the pitcher to the final drink size cold, it would overflow once foamed. Starting below the target leaves room for the foam to form.
Does the milk type change the numbers?
Somewhat. Whole dairy milk foams richly and predictably; skim froths more but drier; many plant milks (especially barista oat) foam well while others expand less. Treat the expansion factors as starting points and adjust to your milk.
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This calculator is for educational purposes. Double-check important results before acting on them.