15 cm / 6 in round vs 18 cm / 7 in round
| 15 cm / 6 in round | 18 cm / 7 in round | |
|---|---|---|
| Size | 15 cm across | 18 cm across |
| Base area | 176.7 cm² | 254.5 cm² |
| Usual depth | 5 cm | 5 cm |
| Holds | 0.88 L | 1.27 L |
Can you swap them?
Scale the mixture, or accept a flatter cake. 18 cm / 7 in round has 44% more area, so a 15 cm / 6 in round mixture poured straight in sits 69% as deep. It still bakes, and it browns more at the edges for being shallower. Multiplying by 1.44 restores the depth the recipe was written for.
Scaling the recipe
| Recipe written for | Baked in | Multiply by | Or leave it and get |
|---|---|---|---|
| 15 cm / 6 in round | 18 cm / 7 in round | 1.44 | 69% of the depth |
| 18 cm / 7 in round | 15 cm / 6 in round | 0.69 | 144% 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 69% as deep is done earlier, not cooler. Leave the temperature alone, start testing at about 69% 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 18 cm / 7 in round instead of a 15 cm / 6 in round?
Yes, with the mixture multiplied by 1.44. 18 cm / 7 in round has 254.5 cm² of base against 176.7 cm², so an unscaled 15 cm / 6 in round recipe sits 69% as deep and bakes faster.
What is the difference between a 15 cm / 6 in round and a 18 cm / 7 in round?
15 cm / 6 in round has a base area of 176.7 cm² and 18 cm / 7 in round has 254.5 cm² — 18 cm / 7 in round is 44% larger. At their usual depths they hold 0.88 L and 1.27 L.
Do I need to change the baking time between a 15 cm / 6 in round and a 18 cm / 7 in round?
Yes. Moving a 15 cm / 6 in round mixture into 18 cm / 7 in round makes it 69% as deep, so start checking at about 69% of the stated time. Depth drives baking time far more than tin diameter does.
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