How to Adapt a Recipe to a Different Cake Tin Size
Adapting a recipe to a different tin size is one of the questions I’m asked most often. So below you’ll find the most common tin shapes used in pastry and the formulas that apply to each, so you can confidently make a cake bigger or smaller than the recipe states. These adjustments get easier and more intuitive as you gain experience.
The rule: divide the area (or volume) of the tin you want to use by the area (or volume) of the tin in the recipe. The result is the correction factor (k). Multiply every ingredient quantity by this factor. If your tin is bigger, k will be above 1; if it’s smaller, k will be below 1.
Round tins with different diameters, same height
The recipe is for a 20cm tin and you need an 18cm one. Compare the area of each circle (π × r²):
- 20cm tin: 3.14 × (10 × 10) = 314 (10 is the radius)
- 18cm tin: 3.14 × (9 × 9) = 254 (9 is the radius)
- k = 254 ÷ 314 = 0.81
Multiply every ingredient by 0.81. Going the other way – a recipe for 18cm that you want to make in a 20cm tin – k = 314 ÷ 254 = 1.23.
Square tins with different sides, same height
The recipe is for a 20cm square tin and you need an 18cm one. Compare the area of each square (side²):
- 20cm tin: 20 × 20 = 400
- 18cm tin: 18 × 18 = 324
- k = 324 ÷ 400 = 0.81
From 18cm to 20cm: k = 400 ÷ 324 = 1.23.
Round vs square tin, same height
The recipe is for a 20cm round tin and you need a 16cm square one:
- 20cm round: 3.14 × (10 × 10) = 314
- 16cm square: 16 × 16 = 256
- k = 256 ÷ 314 = 0.81
From a 16cm square to a 20cm round: k = 314 ÷ 256 = 1.22.
Round vs rectangular tin, same height
The recipe is for a 20cm round tin and you need a 35 × 25cm rectangular one:
- 20cm round: 3.14 × (10 × 10) = 314
- 35 × 25cm rectangle: 35 × 25 = 875
- k = 875 ÷ 314 = 2.78
From the rectangle to a 20cm round: k = 314 ÷ 875 = 0.36.
Tins with different heights
If the heights differ, calculate the correction factor using the volume of each tin:
- Round tin: V = π × r² × h (h is the height of the tin or finished cake)
- Cube: V = L³ (L is the side)
- Rectangular tin: V = L × W × h (length × width × height)
Example: the recipe is for a 20cm round tin, 8cm high, and you need a 35 × 25cm rectangular tin, 6cm high.
- Round: 3.14 × (10 × 10) × 8 = 2,512
- Rectangular: 35 × 25 × 6 = 5,250
- k = 5,250 ÷ 2,512 = 2.09
From the rectangular tin back to the 20 × 8cm round: k = 2,512 ÷ 5,250 = 0.48.
One last tip: baking times change with tin size, too. A larger, shallower cake bakes faster; a deeper one needs a lower temperature and more time – always check with a skewer. For more on adjusting recipes, see 5 common pastry mistakes.
Want to bake like a pro? Learn professional layered cakes step by step with our online courses and ebooks – from Red Velvet to Caramel Carrot Cake. Browse the courses →
