Cake Size Conversion Guide

Convert 8" Cake to 6" Cake

So you've got a recipe for an 8" cake and need it to fit a 6" tin instead.

Do you just halve everything? 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.

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Here's the simple version:

  • Ingredients need scaling down based on tin size
  • Baking time usually needs adjusting too

Scaling from 8" to 6"

For round tins, it's based on surface area, not just the number written on the tin.

Going from 8" to 6" is usually about 0.55x to 0.6x the recipe (assuming similar depth).

Example

Here's what that looks like in practice

From 2 x 8" tins to 2 x 6" tins - same recipe, just adjusted to fit.

Original Recipe

Chocolate Sponge

Original 2 x 8" (20cm) Tins

  • Cocoa Powder55g
  • Boiling Water6 tbsp
  • Eggs4
  • Butter225g
  • Caster Sugar225g
  • Self-Raising Flour225g
  • Baking Powder1 tsp
Scaled for Your Tin

Perfectly Scaled

New 2 x 6" (15cm) Tins

  • Cocoa Powder30g
  • Boiling Water3 1/2 tbsp
  • Eggs2
  • Butter125g
  • Caster Sugar125g
  • Self-Raising Flour125g
  • Baking Powder1/2 tsp
Anna

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 earlier than you think, because smaller tins can bake faster.

Want to do this with your own recipe? You can paste it in here and it'll work it all out.

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Common 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.

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