Find the ingredient multiplier when changing baking pan size
When you do not have the pan size a recipe calls for, you need to adjust the ingredient quantities proportionally to the change in pan area. The batter depth should remain approximately the same — if you put the same amount of batter in a larger pan, it will be too shallow and overcook; in a smaller pan, it will be too deep and undercook.
Multiplier = Target pan area ÷ Original pan area
For round pans: Area = π × radius². For rectangular/square pans: Area = length × width.
| Original pan | Target pan | Multiplier | Time adjustment |
|---|---|---|---|
| 20cm (8") | 23cm (9") | × 1.32 | −5 min |
| 20cm (8") | 25cm (10") | × 1.56 | −8 min |
| 23cm (9") | 20cm (8") | × 0.76 | +5 min |
| 23cm (9") | 25cm (10") | × 1.18 | −3 min |
| 2 × 20cm rounds | 1 × 33×23cm sheet | × 1.0 | Same time |
| Pan diameter | Area (cm²) | Area (in²) |
|---|---|---|
| 15cm (6") | 177 cm² | 28 in² |
| 20cm (8") | 314 cm² | 50 in² |
| 23cm (9") | 415 cm² | 64 in² |
| 25cm (10") | 491 cm² | 79 in² |
| 28cm (11") | 616 cm² | 95 in² |
| 30cm (12") | 707 cm² | 113 in² |
When you change pan size, baking time changes because the batter depth changes. A larger pan produces a shallower batter that bakes faster; a smaller pan produces deeper batter that takes longer. As a guideline, start checking 10–15% earlier when using a larger pan and add 10–15% time when using a smaller pan. Always check doneness with a skewer or thermometer rather than relying only on time.
Deeper batter in a smaller pan sometimes benefits from a slightly lower temperature (reduce by 10–15°C) to allow the centre to cook before the edges over-brown. This is particularly relevant for dense cakes and brownies. Shallower batter in a larger pan rarely needs temperature adjustment.
A 20cm (8") square pan has an area of 400 cm², compared to 314 cm² for a 20cm round pan — the square is about 27% larger. For a recipe written for a 20cm round pan, use a 18cm square pan (area 324 cm²) for the closest match, or scale up ingredients by 1.27 for the 20cm square.
Yes — if the combined area of the two pans equals the original pan area, no ingredient adjustment is needed. Two 20cm round pans (2 × 314 = 628 cm²) are approximately equivalent to one 28cm round pan (616 cm²). Baking time will be shorter since the batter is shallower.
Yes — dark metal pans absorb more heat and brown food faster than light metal pans. Glass and ceramic pans retain heat longer and may require reducing temperature by 10–15°C. Non-stick pans reduce sticking but may produce slightly different browning. For best results, use the pan material the recipe specifies.
Calculate the area of both pans and use the ratio as your multiplier. For rectangular pans, multiply length by width. For round pans, multiply π (3.14159) by the radius squared. Then adjust quantities accordingly.
A standard 23×13cm loaf pan has approximately 300 cm² of base area. A 12-cup muffin tin produces 12 individual portions — scale the loaf recipe by 0.8–0.9 for a 12-cup tin (muffins are typically smaller). Baking time will be much shorter — 18–22 minutes instead of 50–60 minutes.