Baking tin sizes
22 common tins with their real area and volume, and the substitution each one allows.
A recipe is written for an area, not a name
This is the whole thing. Batter poured into a wider tin is shallower; a shallower cake cooks through sooner and browns more at the edges. So the question is never "is my tin close enough in inches" but "how much does the area change".
A 20 cm round is 314 cm² and a 23 cm round is 415 — 32% more. Three centimetres of diameter sounds like nothing and is a third of the tin, because area goes with the square of the radius. The same batter comes out 0.76 times as deep and wants checking ten minutes early.
The familiar substitution works for the same reason: a 9 × 13 inch tin is 755 cm² and two 23 cm rounds are 831 — within 9%, which is why so many recipes offer both.
The rule of thumb
| Area difference | What to do |
|---|---|
| Within 10% | Nothing. Bake as written. |
| 10–25% larger | Shallower and faster — start checking 10 minutes early. |
| 10–25% smaller | Deeper and slower — add 10 to 15 minutes, and drop the temperature 10 °C if the top browns first. |
| More than 25% either way | Scale the recipe rather than the time. |
Every tin
| Tin | Size | Area | Volume |
|---|---|---|---|
| 15 cm / 6 in round | 15 cm across | 177 cm² | 0.9 L |
| 18 cm / 7 in round | 18 cm across | 254 cm² | 1.3 L |
| 20 cm / 8 in round | 20 cm across | 314 cm² | 1.6 L |
| 23 cm / 9 in round | 23 cm across | 415 cm² | 2.1 L |
| 25 cm / 10 in round | 25 cm across | 491 cm² | 2.5 L |
| 28 cm / 11 in round | 28 cm across | 616 cm² | 3.1 L |
| 30 cm / 12 in round | 30 cm across | 707 cm² | 3.5 L |
| 18 cm / 7 in square | 18 × 18 cm | 324 cm² | 1.6 L |
| 20 cm / 8 in square | 20 × 20 cm | 400 cm² | 2.0 L |
| 23 cm / 9 in square | 23 × 23 cm | 529 cm² | 2.6 L |
| 23 × 33 cm / 9 × 13 in | 23 × 33 cm | 755 cm² | 3.8 L |
| 20 × 30 cm traybake | 20 × 30 cm | 600 cm² | 2.7 L |
| Loaf 21.5 × 11.5 cm / 8½ × 4½ in | 22 × 12 cm | 247 cm² | 1.6 L |
| Loaf 23 × 13 cm / 9 × 5 in | 23 × 13 cm | 299 cm² | 2.1 L |
| Springform 18 cm / 7 in | 18 cm across | 254 cm² | 1.7 L |
| Springform 20 cm / 8 in | 20 cm across | 314 cm² | 2.0 L |
| Springform 23 cm / 9 in | 23 cm across | 415 cm² | 2.7 L |
| Springform 26 cm | 26 cm across | 531 cm² | 3.5 L |
| Bundt 25 cm / 10 in | 25 cm across | 491 cm² | 4.7 L |
| Tart 23 cm / 9 in | 23 cm across | 415 cm² | 1.0 L |
| Swiss roll 25 × 38 cm | 25 × 38 cm | 950 cm² | 1.9 L |
| Half sheet 33 × 46 cm / 13 × 18 in | 33 × 46 cm | 1,518 cm² | 3.8 L |
"20 cm" and "8 inch" are not the same tin
Eight inches is 203 mm and 20 cm is 200. Tins are sold under both names, manufacturers build to whichever their market uses, and the two are 3 mm apart in diameter and about 3% apart in area. The same goes for 25 cm against 10 inches (250 vs 254 mm) and 30 cm against 12 (300 vs 305).
Three per cent is inside the tolerance of any recipe, so it never matters on its own. It matters when it compounds — a European 20 cm tin used for an American recipe written for 8 inches, baked in an oven running 10 °C cool, with a fan the recipe did not account for. Each of those is small and the three together are not.
Depth matters as much as width
Two tins with the same area are not always interchangeable. A tart tin is 25 mm deep and a springform is 65 mm; the same filling in the shallower one is spread three times as thin and behaves completely differently. Where a recipe specifies a tart tin or a Swiss roll tin, the depth is the reason, and a cake tin of the same diameter will not do.