20 cm / 8 in square tin
400 cm² · 2.0 litres
20 × 20 cm · 62.0 in² · 50 mm deep · rectangular
About this tin
The standard brownie and traybake tin. Its area is close to a 23 cm round, which is why recipes often offer both.
The numbers
| Dimensions | 20 × 20 cm · 7.9 × 7.9 in |
| Depth | 50 mm · 2.0 in |
| Base area | 400 cm² · 62.0 in² |
| Volume to the rim | 2.0 litres |
| Usable batter | about 1.2 litres — filled to roughly two thirds |
What can replace a 20 cm / 8 in square
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 |
|---|---|---|---|
| 23 cm / 9 in round | 415 cm² | +4% | Interchangeable — no change needed |
| Springform 23 cm / 9 in | 415 cm² | +4% | Interchangeable — no change needed |
| Tart 23 cm / 9 in | 415 cm² | +4% | Interchangeable — no change needed |
| 18 cm / 7 in square | 324 cm² | -19% | Batter 1.23× as deep — allow 9–19 minutes longer |
| 20 cm / 8 in round | 314 cm² | -21% | Batter 1.27× as deep — allow 11–21 minutes longer |
| Springform 20 cm / 8 in | 314 cm² | -21% | Batter 1.27× as deep — allow 11–21 minutes longer |
| 25 cm / 10 in round | 491 cm² | +23% | Batter 0.81× as deep — check 11–23 minutes early |
| Bundt 25 cm / 10 in | 491 cm² | +23% | Batter 0.81× as deep — check 11–23 minutes early |
Frequently asked questions
What is the area of a 20 cm / 8 in square tin?
400 cm² (62.0 in²), holding roughly 2.0 litres filled to 50 mm.
Can I use a different tin instead of a 20 cm / 8 in square?
The closest here is 23 cm / 9 in round at 415 cm² — 4% more area, so the mixture sits shallower and bakes faster. 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 square tin hold?
About 2.0 litres to a depth of 50 mm. Cake batter is normally filled to between half and two thirds, so 1.2 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 square for a 23 cm / 9 in round changes the depth by a factor of 0.96.
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