Cake Tin Size Converter
Recipes are not always written for the tin you own, and swapping between round and square tins without adjusting the size can leave your cake too shallow, too deep, or baked for the wrong amount of time. Enter your recipe's tin size below to find the equivalent.
Convert your cake tin size
Enter the tin size your recipe calls for, and the shape you actually want to use.
For the same baking area, use a square tin around:
17.5cm
Nearest common UK sizes: 15cm, 18cm.
This tin is smaller than your recipe's original, so the mixture will sit deeper and may need slightly longer in the oven.
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Frequently asked questions
Why do I need to convert between round and square tin sizes?
A round and a square tin of the same "size" hold noticeably different amounts of mixture, because a square tin has more area than a round tin with the same width. Matching the baking area rather than the labelled size keeps the depth of your bake close to what the recipe expects.
What happens if I use a bigger tin than the recipe calls for?
The same amount of mixture will spread out thinner in a larger tin, so it will cook faster and may dry out if you bake it for the full time stated. Start checking it a little earlier than the recipe suggests.
What happens if I use a smaller tin than the recipe calls for?
The mixture will sit deeper in a smaller tin, which usually means a longer bake time and a greater risk of the outside browning before the middle is fully cooked. It can help to cover the top loosely with foil partway through.
Does this conversion work for all cake types?
It works well for most sponge and traybake mixtures, where the goal is a consistent depth of batter. Very delicate bakes like soufflés or those needing precise tin proportions may need more careful adjustment beyond just matching area.
How this calculator works
The calculator first determines the surface area of your original round cake tin. We use the formula: Surface Area = π * (radius)² where ‘π’ is approximately 3.14159 and the radius is half the diameter of the tin. It then calculates the equivalent surface area for a square tin using the formula: Surface Area = side * side, where ‘side’ is the length of one side of the square. Finally, it uses these calculated areas to determine the scaling factor needed to adjust your recipe quantities. The calculator assumes that you are converting between tins with identical heights.
Square Tin Sizes & Baking Performance – A UK Guide
| Tin Size (cm) |
|---|
| 8 inch (20.3 cm) |
| 10 inch (25.4 cm) |
| 12 inch (30.5 cm) |
Worked example: Converting a Sponge Cake Recipe
Let’s say you're making a Victoria sponge recipe that calls for 200ml of liquid and needs to be baked in an 8-inch (20.3cm) round tin. The calculator determines the surface area of this tin is approximately 50.27 cm². The calculator then calculates the equivalent surface area needed for a square tin with sides of 10 inches (25.4cm), which is 254 cm².
More questions answered
What units does this calculator use?
The calculator uses centimetres (cm) for dimensions and millilitres (ml) for liquid ingredients. You can easily convert to other units in your recipe if needed, but ensure you maintain consistency throughout.
How accurate is this conversion?
The accuracy depends on the original recipe's proportions and tin sizes. This calculator provides a good approximation based on equal surface area, but slight variations may occur due to differences in tin shape or baking behaviour.
Can I use this for other shapes besides round and square?
This calculator is specifically designed for converting between round and square tins. Other shapes (e.g., rectangular) require a more complex calculation taking into account all dimensions.
What if my tin isn’t perfectly square or round?
The accuracy will be reduced if your tins are significantly irregular. For the most precise conversion, use tins with standard dimensions and adjust ingredient quantities accordingly.
Does this calculator handle different cake recipes?
Yes, it works for any recipe where liquid ingredients are the primary factor in baking volume. However, recipes relying heavily on dry ingredients (like brownies) may require a more nuanced approach.
What if I’m scaling up or down a recipe?
The calculator automatically adjusts for changes in scale. If you double the recipe, it will double the ingredient quantities based on the calculated surface area adjustments – simply input the new values.
Can I use this to convert between different tin materials (e.g., metal vs silicone)?
The calculator focuses purely on surface area and doesn’t account for material differences, which can affect heat conductivity and baking times. These factors should be considered separately.
How do I ensure my cake rises correctly after conversion?
After converting your recipe, pay close attention to oven temperature and baking time. It's always advisable to check for doneness with a skewer – the result may require slight adjustments based on the new tin size.
I’ve made a mistake in the input values; how can I correct it?
Simply enter the corrected values into the calculator, and the results will automatically update. Double-check your inputs to avoid further errors.
What is the maximum tin size this calculator supports?
The calculator has a maximum input for square tin side lengths of 30.5cm (12 inches). Larger tin sizes require a more complex calculation and are not supported by this tool.