Cake Size Conversion Guide
Convert 8" Cake to 10" Cake
So you've got a recipe for an 8" cake and need it to fit a 10" tin instead.
Do you just double it? Do you guess? And what happens to the baking time?
Skip The Guesswork
Want to do this with your own recipe?
Instead of charts and manual multipliers, drop your recipe into our Just Bakes web app, choose your tins, and let the app do the tricky bit for you.
Here's the simple version:
- Ingredients need scaling up based on tin size
- Baking time usually needs adjusting too
Scaling from 8" to 10"
For round tins, it's based on surface area, not just the number written on the tin.
Going from 8" to 10" is usually about 1.5x to 1.6x the recipe (assuming similar depth).
Example
Here's what that looks like in practice
From 2 x 8" tins to 2 x 10" tins - same recipe, just adjusted to fit.
Victoria Sponge
Original 2 x 8" (20cm) Tins
- Free-range Eggs4
- Caster Sugar225g
- Self-Raising Flour225g
- Baking Powder1 tsp
- Baking Spread225g
Perfectly Scaled
New 2 x 10" (25cm) Tins
- Free-range Eggs6
- Caster Sugar350g
- Self-Raising Flour350g
- Baking Powder1 1/2 tsp
- Baking Spread350g
This is exactly where the app saves time. No spreadsheet, no chart-hunting, no awkward maths.It's still a guide, so keep an eye on it, but this gets you very close without the guesswork.
What about baking time?
Even if the cake is the same depth, changing tin width changes how heat reaches the middle, so bake time usually shifts too.
Best approach: start checking a little earlier than you think, then keep an eye on it from there.
Want to do this with your own recipe? You can paste it in here and it'll work it all out.
Try It NowCommon mistakes
This is where it usually goes a bit wrong:
- Scaling ingredients but forgetting bake time
- Using a fixed chart and hoping it works
- Not accounting for tin depth or shape
- Ending up with things like 1.3 eggs and not knowing what to do next
Why charts and basic calculators can be hit and miss
Most charts give a rough multiplier and leave the rest to you.
They usually don't account for shape, depth, or how the cake actually behaves in the oven. And some calculators return awkward amounts that are technically right, but not very useful in a real kitchen.
A simpler way
If you'd rather skip the manual maths, just add your recipe, pick your tins, and let the app handle the tricky part.
You'll get ingredient amounts that are practical to use, plus bake time and temperature guidance to match.
No maths. No guesswork.
Come say hi on WhatsApp
I share updates and new features there first. If you need a hand or there's something you'd love the app to do, pop in and let me know.