Cake pan sizes: capacities, swaps and how much batter each one holds
Key takeaways
- Pans are volumes: base area times depth decides what a batter experiences.
- Round 20 cm ≈ square 18 cm is the classic safe swap; diameter alone misleads.
- Never fill beyond two-thirds — the last third belongs to the rise.
- Surplus batter has a home: muffins, at about two-thirds the time.
A recipe's pan size is not a serving suggestion — it is part of the formula. The same batter spread thin bakes in twenty minutes and dries; piled deep, it domes, cracks and stays raw-hearted. Yet cupboards hold the pans they hold, and recipes ask for the one you lack with suspicious regularity.
This guide gives the working capacities of the pans home bakers actually own, the swaps that are safe, the swaps that change the bake, and the one measurement — depth — that decides which is which.
Capacity is the number that matters
Pans are labelled by their top measurement — a '20 cm round' — but a batter experiences a pan as a volume: base area times depth. A 20 cm round at 5 cm deep holds roughly 1.6 litres of batter comfortably (filled two-thirds). Move that batter to a 23 cm square and it covers the base at barely 3 cm deep; it needs about a third more mixture to bake at the same depth, or it bakes as a different, thinner cake.
This is why lists of 'equivalent pans' that match only surface area mislead: two pans can share an area and differ in depth by half. The converter on this site holds both dimensions for each pan and ratios the volumes, which is the comparison a batter actually makes.
The safe swaps
Within a family, swaps are gentle. A 20 cm round and an 18 cm square hold near enough the same — a long-standing equivalence that works because their base areas are close and their depths usually match. A 23 cm round exchanges with a 20 cm square on the same basis. Springform for solid round, at the same diameter, changes nothing except your afternoon's washing up and the cake's exit strategy.
Loaf pans swap by weight of dough: a 900 g (2 lb) loaf tin suits doughs of 800 g to 1 kg total, a 450 g tin about half that. A recipe giving total dough weight has quietly given you its pan size, whatever tin it pictures.
The swaps that change the bake
Shape changes heat. A bundt's central tube pushes heat into the middle of a ring of batter, so bundt mixtures are formulated rich and moist to suit it; pour an ordinary sponge into a bundt and it can dry at the edges before the ring sets. A traybake spreads a cake mixture across a wide, shallow pan — wonderful for feeding a class, but the same mixture wants a shorter bake and gives a bar, not a slice.
Muffin tins are the forgiving destination for surplus: any cake batter becomes muffins at roughly two-thirds the original time, checked by eye. Conversely, batter designed for muffins, risen quickly and baked hot, makes a coarse full-size cake. Direction matters.
Filling, lining and the two-thirds rule
Whatever the conversion says, fill a pan no more than two-thirds. The remaining third is the rise's room and the insurance against the oven's enthusiasm; a pan filled to the brim does not produce a bigger cake, it produces an oven floor to clean and a cake with a muffin top it never wanted.
Lining is part of capacity, in a small way: a paper collar standing above a fruit cake's tin both protects the top and effectively deepens the pan for a long bake. And when a recipe matters, the surest capacity check is water: fill the intended pan to the depth the recipe implies, measure the water, compare it with the original pan the same way. Kitchens measured things long before charts.
| Pan | Base area | Approx. batter |
|---|---|---|
| Round 15 cm / 6 in | 177 cm² | 0.6 L |
| Round 20 cm / 8 in | 314 cm² | 1.0 L |
| Round 23 cm / 9 in | 415 cm² | 1.4 L |
| Square 20 cm / 8 in | 400 cm² | 1.3 L |
| Square 23 cm / 9 in | 529 cm² | 1.8 L |
| Loaf 900 g / 2 lb | 299 cm² | 1.2 L (dough 800 g–1 kg) |
| Rectangular 33 × 23 cm | 759 cm² | 2.5 L |
| Muffin tin, 12 cups | — | 0.9 L total |
Working capacities (batter, two-thirds full)
The 20 cm round that became a 23 cm square
A birthday sponge is written for a 20 cm round: 200 g each of flour, sugar and butter, 4 eggs. Your only clean tin is a 23 cm square. Areas: 314 cm² against 529 cm² would demand ×1.7 at identical depth — too much; but the square tin is shallower (5 cm against the round's deeper sandwich tins), and on volume at working depth the ratio settles near ×1.35. Scale by 1.35 — 270 g lines, eggs to 5½ by weight — check five minutes early, and the square cake eats like the round one, corners included.
Common mistakes
Swapping by diameter alone. A 23 cm pan is not ‘a bit bigger’ than a 20 cm — its area is a third larger. Judging by the number on the box under-converts almost every swap.
Filling to the top to compensate. Overfilling to fake depth gives overflow and a sunken centre. If there is not enough batter for the pan, the honest answers are a smaller pan or a scaled recipe.
Ignoring the muffin-tin escape route. Leftover batter from an undersized swap has a perfect home: two or three muffins, baked alongside. Throwing it away, or cramming it in, are both worse.
Questions, answered
Can I bake a round recipe in a square tin for the corners?
Yes — corners are a legitimate ambition. Use the volume ratio, scale the recipe, and expect the corners to bake a touch faster; they are also the cook’s tax.
My tin is 21 cm, between sizes. Which conversion do I use?
Treat it as the 20 cm figure plus a tenth: add roughly 10% to the recipe, or accept a slightly thinner cake at the standard amounts. Mid-size tins are forgiving within that margin.
How deep should batter be?
For most sponges, 3–5 cm of raw batter is the happy range. Below that it bakes dry and quick; above it, allow more time and a little less heat.
The short version
Once pans are thought of as volumes rather than names, swaps stop being gambles. Compare capacities, scale to keep depth constant, fill to two-thirds, and check a little early — and the cupboard you have becomes the cupboard every recipe was written for.
Put it into practice
The tool this article leans on: Baking Pan Converter — Move a recipe to a different pan without overflowing it. Open it alongside “Cake pan sizes: capacities, swaps and how much batter each one holds” and run the numbers for your own bake.
Open the Baking Pan Converter →