Cake-tin size converter
Find the square cake tin size with the same baking area as a round tin, so you can substitute one for the other without changing the recipe's baking time too much.
Result
Equivalent square tin side
Baking area
How to use this calculator
- Enter the round tin's diameter.
- Read the equivalent square tin side length with the same baking area.
Assumptions
- Matches baking area only, not depth — use a tin of similar depth too, or adjust baking time if the depths differ noticeably.
Technical details: what the fields mean
- Round tin diameter
roundDiameter - Diameter of the round tin, measured across the inside top edge.
Methodology
Round tin area = π × radius². Equivalent square side = √(area) — the side length of a square with the same total baking area.
Worked example
20cm round tin
Inputs: roundDiameter=20
Result: 17.7cm square tin (same ~314cm² area)
Practical guidance
- A cake baked in a squarer tin of the same area often needs a very similar baking time — check for doneness a few minutes early just in case, since corners can cook slightly faster than curves.
Common mistakes
- Matching a round tin's diameter directly to a square tin's side length, which actually gives the square tin significantly more baking area (and a thinner, faster-cooking cake) than intended.
FAQs
What square tin is equivalent to a 20cm round tin?
About 17.7cm × 17.7cm, matching the same baking area.