Cake Tin Size Converter
Enter the tin the recipe asks for and the tin you actually own to see how much to scale the recipe.
Answer
Multiply every ingredient by 1.27 (about 27% more mixture).
The detail
Tins are compared by the area of their base, not their width, which is why a 20 cm square tin holds noticeably more than a 20 cm round one.
Reference and detail
Area, not width
Tins are compared by the area of their base. A 20 cm square tin has about 27% more area than a 20 cm round tin, so the same mixture would come out noticeably shallower.
Timing
Keep the oven temperature the same. A shallower cake bakes faster and a deeper one slower, so check with a skewer rather than trusting the original time.
Questions and answers
Questions about converting cake tin sizes
Can I use a 23cm tin instead of a 20cm tin?
Yes, but you need to scale the recipe rather than just baking it as written. A 23cm round tin holds noticeably more than a 20cm one, because the difference in area is bigger than the difference in width suggests.
Enter both sizes above to get the multiplier for every ingredient and how the baking time is likely to change.
Can I convert a round tin size to a square tin?
Yes. The calculator compares the base area of the two tins, whatever their shape, so you can convert round to square or square to rectangular in one step.
A square tin holds more cake than a round tin of the same width, so swapping shapes at the 'same' size still changes the amount of mixture you need.
Does the depth of the tin matter, not just the width?
The multiplier above is based on the base area, because that is what most recipes are written against. A much deeper or shallower tin than the one specified will still change how full it gets and how long the middle takes to set, so watch the mixture level once it goes in and don't fill any tin more than about two-thirds full.
Do I need to change the oven temperature for a different tin size?
No. Keep the oven temperature the same as the recipe states. What changes is the baking time: a wider, shallower tin bakes faster, and a smaller, deeper tin takes longer.
The advice above tells you which way to adjust your timing and when to start checking.
How much more mixture does a larger tin need?
Enter your two tin sizes above for the exact multiplier. It depends on both tins, so there's no single figure that fits every swap.
As a rule of thumb, a small increase in width can mean a much bigger increase in area, which is why tins that look similar in size can need noticeably different amounts of batter.
Guidance
Read the full guide
- Cake Tin Sizes and Recipe ScalingHow to bake a recipe in the tin you actually own: matching area rather than width, adjusting batter quantity, and what happens to the baking time.