Why does tin size affect baking time?

When you use a different tin size with the same amount of batter, the depth changes. A larger tin gives shallower batter that bakes faster. A smaller tin gives deeper batter that needs longer, often at a slightly lower temperature, to cook through without burning the outside.

Should I change the oven temperature too?

For significantly deeper batters (a much smaller tin), reduce the temperature by 10-15°C to give the centre time to cook without over-browning the crust. For a larger, shallower tin, keep the same temperature and simply start checking earlier — increasing the heat is not recommended as it risks burning the top before the inside is set.

How accurate is this calculation?

This gives an indicative estimate only — the exact timing depends on your oven, the recipe and the tin material. Always check your cake 5-10 minutes before the calculated time. Insert a skewer into the centre — if it comes out clean, the cake is done. Ovens vary significantly, so visual and skewer checks are essential.

Does this work for any type of cake?

Yes, the principle applies to sponges, fruit cakes, and brownies. However, very dense cakes like fruit cakes are more sensitive to depth changes and may need proportionally more extra time when made deeper.

Should I adjust the temperature as well as the time?

For small changes in tin size (within 5cm), adjusting the time alone is usually enough. Moving to a much smaller, deeper tin gives a deeper batter, so reduce the temperature by 10-15 degrees C and allow a little more time to stop the outside overcooking before the centre is done. Moving to a larger, shallower tin bakes faster, so keep the same temperature and reduce the time, checking early with a skewer.

Baking Time Adjustment Calculator — Free Online Tool

How We Calculate This

Baking time is influenced by the depth of the batter. When you change tin size, the batter depth changes even if the recipe quantity stays the same. This calculator estimates the new baking time based on the area ratio between the original and new tin. The result is an indicative estimate, not an exact figure — ovens, recipes and tin materials all vary, so always check with a skewer.

The Approach

Round tin area = π × (diameter ÷ 2)²; square tin area = side². A square tin holds about 27% more than a round of the same dimension (its corners add area).
Calculate the area ratio: new tin area ÷ original tin area
A ratio above 1 means a larger, shallower bake (less time needed)
A ratio below 1 means a smaller, deeper bake (more time needed)
Time adjustment follows a diminishing-rate power curve on the inverse of the area ratio (default exponent 0.3, tunable in advanced options)

Temperature Notes

Larger, shallower tin: keep the same temperature and start checking earlier
Significantly smaller, deeper tin: reduce the temperature by 10-15°C so the centre cooks before the crust over-browns, and allow a little more time

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Last updated: February 2026

All calculations are based on standard ratios and conversions. Results may vary with specific ingredients, equipment, and conditions.

Baking Time Adjustment Calculator

Original Recipe

New Tin