Guide · In the kitchen
Recipe Scaling Calculator
Updated: June 2026
A recipe written for four can feed six, or two, without any guesswork — every ingredient is in direct proportion to the number of servings. The rule of three turns “how much flour for 6 instead of 4?” into a one-line calculation. This guide shows the scaling factor method, how to halve and double cleanly, and the few things that do not scale.
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The scaling factor
Find one number — the scaling factor — and apply it to every ingredient. It is simply the new servings divided by the original:
new amount = original amount × factor
Going from 4 to 6 servings, the factor is 6 ÷ 4 = 1.5. So 200 g flour becomes 200 × 1.5 = 300 g, 2 eggs become 3, 100 ml milk becomes 150 ml. Because all ingredients share the same factor, the balance of the recipe — and the taste — is preserved.
Per-ingredient rule of three
If you prefer not to compute a factor, the rule of three handles each ingredient directly:
6 servings → x g flour
x = 200 × 6 ÷ 4 = 300 g
Drop the three numbers into the calculator's Direct mode and read the answer. Repeat for each ingredient, or just reuse the single factor — both give the same result.
Doubling and halving
The most common adjustments have tidy factors. To double, multiply everything by 2; to halve, multiply by 0.5; for one-and-a-half batches, by 1.5. Halving sometimes lands on awkward amounts — half an egg, for instance. There, beat one egg and use half by weight, or round to the nearest sensible quantity, since baking tolerates small deviations in the binding ingredients better than in the leavening.
Scaling by pan size
To fit a different tin, scale by area, not by length. A round tin's capacity grows with the square of its diameter. Moving from an 8-inch to a 10-inch round, the area ratio is 10² ÷ 8² = 100 ÷ 64 ≈ 1.56, so multiply the batter by about 1.5. For rectangular tins, compare length × width. Getting this right stops a batter from overflowing or baking too thin.
What does not scale
- Cooking and baking time — a double batch is not cooked in double the time; check for doneness instead.
- Oven temperature — stays the same regardless of batch size.
- Strong seasonings — salt, spices, chilli and yeast often need slightly less than a strict scale, so taste as you go when scaling up a lot.
- Pan depth — more batter in the same tin changes the bake; spread across more tins where possible.
A quick scaling table
| Original (4 servings) | ×1.5 (6) | ×0.5 (2) | ×2 (8) |
|---|---|---|---|
| 200 g flour | 300 g | 100 g | 400 g |
| 2 eggs | 3 | 1 | 4 |
| 150 ml milk | 225 ml | 75 ml | 300 ml |
| 80 g sugar | 120 g | 40 g | 160 g |
Frequently asked questions
How do I scale a recipe to different servings?
For each ingredient: new amount = original × new servings ÷ original servings. The servings ratio is the scaling factor for everything.
How do I double or halve a recipe?
Multiply every ingredient by 2 to double or by 0.5 to halve, keeping the ratios between ingredients the same.
Does cooking time scale too?
No. Ingredients scale directly, but cooking and baking times do not. A bigger batch may need a little longer — check for doneness rather than doubling the clock.