Baking Pan Size Converter

Pan Substitution Guide

Area is What Matters

When swapping pan sizes in a recipe, the thing to match is the base area, not the diameter or the volume. If a cake recipe is designed for a 20 cm round tin (a base area of π × 10² ≈ 314 cm²), then an 18 cm square tin (324 cm²) is a near-perfect substitute, because the batter spreads to about the same depth and bakes in about the same time. A 20 cm square tin (400 cm²) is bigger, so the cake will be shallower and bake faster; a 23 cm round tin (415 cm²) likewise. A worked example: if your recipe calls for a 23 cm round tin but you only have a 20 cm round (which is smaller), the same batter will sit deeper and bake longer — you may need to drop the oven temperature by 10°C and add 5–10 minutes, then check often. Going the other way (smaller recipe in bigger tin) cooks faster because the batter spreads thinner. The classic formula: substitute tin area ÷ original tin area gives the scaling factor, and you can multiply the recipe quantities by that factor to get a cake of the original depth in the new tin. So scaling a 20 cm round (314 cm²) recipe to a 23 cm round (415 cm²) needs about 1.32× the ingredients to give the same depth. This calculator handles the area maths for round, square, and rectangular tins. The same logic applies to loaf tins (length × width × depth gives volume; matching volume rather than length is what matters).

Batter Depth Affects Baking Time

Even after matching the base area, batter depth changes baking time significantly, and this is where many tin substitutions go wrong. More batter in a smaller pan means a deeper cake, which needs longer baking — sometimes much longer — at a slightly lower temperature so the outside doesn't burn before the inside cooks. Less batter in a larger pan means a shallower cake that bakes faster. As a rough rule of thumb: reducing the depth by 25% reduces the baking time by 20–30%; increasing the depth by 25% increases the time by 20–30% and benefits from a 10°C temperature drop. A worked example: a recipe baking at 180°C for 35 minutes in a 20 cm round tin (giving, say, 4 cm cake depth) — if you bake the same batter in a 25 cm round tin (much larger area, much shallower cake), drop the time to about 25 minutes; if you bake in a deeper 18 cm tin (smaller, deeper batter), lower the temperature to 170°C and bake for 45 minutes, checking carefully. Always check doneness with a skewer or temperature probe rather than trusting the time: a clean skewer (no wet batter) means a cake is cooked. Very deep cakes (over 6 cm) sometimes need to be baked at noticeably lower temperatures (160°C) for considerably longer (an hour or more), and may benefit from a tin liner that protects the outside while the inside catches up. For pastry-based bakes (pies, tarts, quiches), depth matters less than for cakes because the cooking is more about setting eggs and crisping pastry than baking through a thick batter.

Tin Volume Guide (UK common)

Knowing standard UK tin sizes and their volumes lets you spot substitutions quickly. Round tins: 18 cm = 254 cm² base, 20 cm = 314 cm², 23 cm = 415 cm², 25 cm = 491 cm², 28 cm = 616 cm². Square tins: 18 cm = 324 cm², 20 cm = 400 cm², 23 cm = 529 cm². Loaf tins are sold by their volume capacity rather than dimensions in the UK: a 450 g (1 lb) loaf tin holds about 450 ml; a 900 g (2 lb) loaf tin (the most common size for bread and cake loaves) holds about 900 ml; a 1.4 kg (3 lb) loaf tin holds about 1.4 litres. For loaf tins, calculate volume directly (length × width × depth in cm gives ml when multiplied), and match volumes rather than dimensions. So a recipe for a 900 g loaf tin (~900 ml) can be made in a roughly 23 × 13 × 7 cm tin (about 2,093 cm³, far too big — you'd get a flat loaf) or about 21 × 12 × 7 cm (1,764 cm³). The standard 900 g loaf tin is roughly 21 × 11 × 6 cm internally, giving ~1,400 ml — but always check, as 'standard' varies between manufacturers. For traybakes and Swiss roll tins, the area is what matters: a typical Swiss roll tin is 23 × 33 cm = 759 cm². For springform tins (releasable sides), the base area is the figure to match. Bundt and ring tins have a hollow centre, so their effective volume is less than a solid tin of the same outer diameter — usually around 2.4 litres for a standard 25 cm Bundt. This calculator helps you match tins by area or volume.

Food Safety Fundamentals

Food safety rules apply regardless of cooking method or time. The danger zone for bacterial growth is 4-60 degrees C — food should not remain in this range for more than 2 hours. Core temperature targets: poultry 74 degrees C throughout (no pink allowed), pork 71 degrees C, beef/lamb can be pink when above 63 degrees C (due to surface-only bacteria on whole cuts). Never use the same equipment for raw and cooked food without washing. Leftovers should be cooled rapidly (within 2 hours), refrigerat