18 cm / 7 in round vs 20 cm / 8 in round
| 18 cm / 7 in round | 20 cm / 8 in round | |
|---|---|---|
| Size | 18 cm across | 20 cm across |
| Base area | 254.5 cm² | 314.2 cm² |
| Usual depth | 5 cm | 5 cm |
| Holds | 1.27 L | 1.57 L |
Can you swap them?
Scale the mixture, or accept a flatter cake. 20 cm / 8 in round has 23.5% more area, so a 18 cm / 7 in round mixture poured straight in sits 81% as deep. It still bakes, and it browns more at the edges for being shallower. Multiplying by 1.23 restores the depth the recipe was written for.
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 |
|---|---|---|---|
| 18 cm / 7 in round | 20 cm / 8 in round | 1.23 | 81% of the depth |
| 20 cm / 8 in round | 18 cm / 7 in round | 0.81 | 123% 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
A mixture 81% as deep is done earlier, not cooler. Leave the temperature alone, start testing at about 81% of the stated time, and let the skewer decide. Why depth sets the time and diameter barely does →
Frequently asked questions
Can I use a 20 cm / 8 in round instead of a 18 cm / 7 in round?
Yes, with the mixture multiplied by 1.23. 20 cm / 8 in round has 314.2 cm² of base against 254.5 cm², so an unscaled 18 cm / 7 in round recipe sits 81% as deep and bakes faster.
What is the difference between a 18 cm / 7 in round and a 20 cm / 8 in round?
18 cm / 7 in round has a base area of 254.5 cm² and 20 cm / 8 in round has 314.2 cm² — 20 cm / 8 in round is 23.5% larger. At their usual depths they hold 1.27 L and 1.57 L.
Do I need to change the baking time between a 18 cm / 7 in round and a 20 cm / 8 in round?
Yes. Moving a 18 cm / 7 in round mixture into 20 cm / 8 in round makes it 81% as deep, so start checking at about 81% of the stated time. Depth drives baking time far more than tin diameter does.
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