20 cm / 8 in round vs 18 cm / 7 in square
| 20 cm / 8 in round | 18 cm / 7 in square | |
|---|---|---|
| Size | 20 cm across | 18 × 18 cm |
| Base area | 314.2 cm² | 324 cm² |
| Usual depth | 5 cm | 5 cm |
| Holds | 1.57 L | 1.62 L |
Can you swap them?
Swap them freely. The areas are within 3.1% of each other, which is less than the variation between two tins of the same nominal size from different manufacturers. Use the recipe as written.
Scaling the recipe
| Recipe written for | Baked in | Multiply by | Or leave it and get |
|---|---|---|---|
| 20 cm / 8 in round | 18 cm / 7 in square | 1.03 | 97% of the depth |
| 18 cm / 7 in square | 20 cm / 8 in round | 0.97 | 103% of the depth |
Multiply every ingredient, including the eggs — round to the nearest half egg and adjust the liquid rather than rounding a whole one up.
Baking time
The depths work out the same here, so use the time as written. Why depth sets the time and diameter barely does →
Frequently asked questions
Can I use a 18 cm / 7 in square instead of a 20 cm / 8 in round?
Yes, with the mixture multiplied by 1.03. 18 cm / 7 in square has 324 cm² of base against 314.2 cm², so an unscaled 20 cm / 8 in round recipe sits 97% as deep and bakes faster.
What is the difference between a 20 cm / 8 in round and a 18 cm / 7 in square?
20 cm / 8 in round has a base area of 314.2 cm² and 18 cm / 7 in square has 324 cm² — 18 cm / 7 in square is 3.1% larger. At their usual depths they hold 1.57 L and 1.62 L.
Do I need to change the baking time between a 20 cm / 8 in round and a 18 cm / 7 in square?
No. The two areas are within 3.1%, so the batter sits at effectively the same depth and bakes in the same time.
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