Recipe Scaler
Paste your ingredient list, set the servings you want, and every quantity rescales — including fractions like 1½ and ranges like 2–3.
Scaling a recipe
Multiply every ingredient by the ratio of the servings you want to the servings the recipe makes. Going from 4 to 6 servings is a factor of 1.5, so 250 g of flour becomes 375 g and 2 eggs become 3. Most ingredients scale linearly and cause no trouble. The exceptions matter though: cooking time, pan size, salt and strong spices do not scale in a straight line, and doubling a cake recipe into the same tin is the most common way a scaled recipe fails.
What does not scale linearly
| Ingredient or factor | How it scales |
|---|---|
| Flour, sugar, liquid, fat | Directly — no adjustment needed |
| Salt | Scale to about 75–80%, then taste. Salt is easy to add and impossible to remove |
| Strong spices, chilli, garlic | Scale to about 75%, then adjust |
| Yeast | Scale to about 75% for large batches — more dough ferments faster |
| Baking powder and soda | Directly up to 2×, then reduce slightly |
| Alcohol and vanilla extract | About 75% — flavour concentrates as volume grows |
| Cooking time | Does not scale. Same temperature, check earlier and often |
| Pan size | Scale by area, not by length. See below |
The pan size trap
This catches almost everyone who doubles a cake recipe. A tin twice as wide holds four times as much, because area grows with the square of the dimension.
| Round tin | Area | Relative capacity |
|---|---|---|
| 15 cm (6 in) | 177 cm² | 1× |
| 20 cm (8 in) | 314 cm² | 1.8× |
| 23 cm (9 in) | 415 cm² | 2.4× |
| 25 cm (10 in) | 491 cm² | 2.8× |
So doubling a recipe made for a 20 cm tin does not mean moving to a 40 cm tin — it means a 28 cm tin, or simply two 20 cm tins. Two tins is usually the safer choice, since batter depth affects how evenly a cake bakes.
Halving a recipe with three eggs
Awkward quantities are the other common problem, and eggs are the worst offender.
To use half an egg: beat one whole egg, weigh it (a large egg is about 50 g without the shell), and use half. Whisking and measuring by tablespoon works too — one large egg is roughly 3 tablespoons.
For anything below about a quarter teaspoon, measuring is not realistic. Use the smallest amount you can manage and taste. This tool switches from fractions to decimals when a quantity gets small, precisely so you can see when you have reached that point.
How to use the Recipe Scaler
- Paste your ingredient list into the left box, one ingredient per line.
- Set what the recipe currently serves and what you want.
- The scaled list appears on the right, with fractions kept readable.
- Copy the result, or press use result as input to scale again.
Frequently asked questions
How do I halve a recipe?
Set "you want to serve" to half the original, or press the Half button. Every quantity is divided, with fractions rendered in cooking-friendly form.
Does cooking time scale too?
No. Keep the same temperature and start checking early. A doubled tray bake in a bigger dish may need slightly longer, but doubling the time will burn it.
What about salt and spices?
Scale them to around 75% of what the maths suggests, then taste and adjust. Seasoning perception does not grow linearly with volume.
Can it handle fractions like 1½?
Yes. Unicode fractions (½, ¾, ⅓), written fractions (1 1/2) and decimals are all understood, and results come back as readable fractions.
What if my recipe uses cups and I want grams?
Scale it here first, then use the cooking converter, which carries per-ingredient densities — a cup of flour and a cup of honey differ by nearly three times in weight.
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Last reviewed September 4, 2026. Results are estimates for general information only.