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.
Nothing standard sits between these two, so this is the smallest change available in this shape.
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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- 18 cm / 7 in square vs 20 cm / 8 in square
- 18 cm / 7 in square vs 23 cm / 9 in square
- 18 cm / 7 in square vs Loaf 23 × 13 cm / 9 × 5 in
- 18 cm / 7 in square vs Springform 20 cm / 8 in
20 cm / 8 in round in full · 18 cm / 7 in square in full · All tin comparisons · All baking tin sizes