Explanation
Scale a recipe up or down
To cook for more or fewer people, multiply every ingredient by the same scale factor: servings wanted divided by servings in the recipe. The amount keeps whatever unit you use, whether grams, cups or teaspoons. Work backwards to find the original amount from a scaled one.
Q′ = Q × s₂ ÷ s₁
| Q | Amount in the original recipe |
|---|---|
| Q′ | Amount in the scaled recipe |
| s₁ | Recipe serves (servings) |
| s₂ | You want to serve (servings) |
250 g of flour in a 4-serving recipe, cooked for 12
| Ingredient amount | 250 |
|---|---|
| Recipe serves | 4 |
| You want to serve | 12 |
| Result | 750 |
Q′ = Q × s₂ ÷ s₁ = 250 × 12 ÷ 4 = 750
k = s₂ ÷ s₁
| k | Scale factor |
|---|---|
| s₁ | Recipe serves (servings) |
| s₂ | You want to serve (servings) |
Turning a 4-serving recipe into 12 servings
| Recipe serves | 4 |
|---|---|
| You want to serve | 12 |
| Result | ×3 |
k = s₂ ÷ s₁ = 12 ÷ 4 = 3
Q = Q′ × s₁ ÷ s₂
| Q | Amount in the original recipe |
|---|---|
| Q′ | Amount in the scaled recipe |
| s₁ | Recipe serves (servings) |
| s₂ | You want to serve (servings) |
750 g in a recipe tripled from 4 to 12 servings
| Scaled amount | 750 |
|---|---|
| Recipe serves | 4 |
| You want to serve | 12 |
| Result | 250 |
Q = Q′ × s₁ ÷ s₂ = 750 × 4 ÷ 12 = 250
Diagram of this result
The diagram writes the scaling as one equation: the original amount, the factor (servings wanted divided by servings in the recipe) and the scaled amount.
Every number in the equation also appears in the answer and the steps, in the unit you entered.
Common mistakes
Cooking time, pan size and oven temperature do not scale by the same factor as ingredients. A deeper pan needs longer, not hotter. Scale each ingredient separately and round only when you measure. Salt, spices and leavening are often reduced slightly in very large batches; taste as you go.
Assumptions and limits
The amount may be zero; both serving counts must be more than zero and may be fractional, since half a batch is meaningful. The calculation is exact proportional arithmetic. It does not adjust timing, fermentation, seasoning or equipment capacity.
Can I scale eggs and other whole items?
Yes, but round to something you can use. Scaling 2 eggs by 1.5 gives 3 eggs; scaling 3 eggs by 1.5 gives 4.5, so beat 5 eggs and leave out about half of one, or weigh them (a large egg is roughly 50 g without the shell).
Sources
Measurement conventions: NIST SP 811, https://www.nist.gov/pml/special-publication-811.