Kitchen
How to convert a cake recipe to a different tin size
Scale by area, not by the tin's diameter.
A 23 cm tin is only 15% wider than a 20 cm tin, but its area is 32% bigger. To keep the same cake depth, multiply every ingredient by the ratio of the base areas. Round tin area = π × d² ÷ 4. Square tin area = side².
Quick reference, from a 20 cm round tin (314 cm²)
| Your tin | Area | Multiply ingredients by |
|---|---|---|
| 18 cm round | 254 cm² | 0.81 |
| 22 cm round | 380 cm² | 1.21 |
| 23 cm round | 415 cm² | 1.32 |
| 25 cm round | 491 cm² | 1.56 |
| 20 cm square | 400 cm² | 1.27 |
| 23 cm square | 529 cm² | 1.68 |
Tips for scaled recipes
1
Round the eggs sensibly
For 3 eggs × 1.32 = 3.96, use 4. For awkward fractions, beat an extra egg and add part of it.
2
Keep raising agents in proportion
Scale baking powder and soda by the same factor.
3
Adjust the baking time, not the temperature
A larger tin at the same depth takes a bit longer. A deeper cake takes noticeably longer. Test with a skewer.
💡 Pro Tip: Fill a tin about two-thirds full. If a scaled batter would fill it higher, use a bigger tin or make a few cupcakes with the extra.
✨ Key Takeaways
- Multiply ingredients by new area ÷ old area.
- A square tin holds about 27% more than a round tin of the same width.
- Change the time, not the oven temperature.
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