20 cm / 8 in round tin
314 cm² · 1.6 litres
20 cm across · 48.7 in² · 50 mm deep · round
About this tin
One of the two sizes almost every cake recipe is written for. If a recipe says "an 8-inch tin" without qualification, this is it.
The numbers
| Diameter | 20 cm · 7.9 in |
| Depth | 50 mm · 2.0 in |
| Base area | 314 cm² · 48.7 in² |
| Volume to the rim | 1.6 litres |
| Usable batter | about 0.9 litres — filled to roughly two thirds |
What can replace a 20 cm / 8 in round
A recipe is written for an area, because area sets the depth and depth sets the baking time. Anything within about 10% needs no adjustment. Past that, change the time first and only then the temperature.
| Tin | Area | vs this one | Effect |
|---|---|---|---|
| Springform 20 cm / 8 in | 314 cm² | +0% | Interchangeable — no change needed |
| 18 cm / 7 in square | 324 cm² | +3% | Interchangeable — no change needed |
| Loaf 23 × 13 cm / 9 × 5 in | 299 cm² | -5% | Interchangeable — no change needed |
| 18 cm / 7 in round | 254 cm² | -19% | Batter 1.23× as deep — allow 10–19 minutes longer |
| Springform 18 cm / 7 in | 254 cm² | -19% | Batter 1.23× as deep — allow 10–19 minutes longer |
| Loaf 21.5 × 11.5 cm / 8½ × 4½ in | 247 cm² | -21% | Batter 1.27× as deep — allow 11–21 minutes longer |
| 20 cm / 8 in square | 400 cm² | +27% | Batter 0.79× as deep — check 14–27 minutes early |
| 23 cm / 9 in round | 415 cm² | +32% | Batter 0.76× as deep — check 16–32 minutes early |
Frequently asked questions
What is the area of a 20 cm / 8 in round tin?
314 cm² (48.7 in²), holding roughly 1.6 litres filled to 50 mm.
Can I use a different tin instead of a 20 cm / 8 in round?
The closest here is Springform 20 cm / 8 in at 314 cm² — 0% less area, so it sits deeper and needs longer. As a rule, anything within about 10% needs no change; beyond that, adjust the time before the temperature.
How much does a 20 cm / 8 in round tin hold?
About 1.6 litres to a depth of 50 mm. Cake batter is normally filled to between half and two thirds, so 0.9 litres of mixture is a working figure.
Why does tin size change the baking time?
Because a recipe is written for a depth, not a name. Heat reaches the centre of a shallow cake sooner, so the same mixture in a wider tin is done earlier and browns more at the edges. The area ratio tells you how much shallower: swapping a 20 cm / 8 in round for a Springform 20 cm / 8 in changes the depth by a factor of 1.00.
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