Day 14 Advent Calendar: Comparing Tin Sizes Using Area Formula

Comparing Christmas Cake Tin Sizes Using Area.

Christmas recipes often assume a specific tin size.

Sometimes tins are measured in inches, so you may need to see our conversion resources.

Today’s Skill that Counts looks at how to compare cake tins using area to help you adjust recipes confidently.

Your recipe uses a 20 cm diameter round tin.

You only have a 25 cm diameter round tin.

You want to know how much larger the new tin is.

Step 1: 

Recall the area formula for a circle

Area = π × radius² (Pi X radius X radius)

Use π ≈ 3.14

If you need any resources to build this "tricky" skill, drop me an email or leave a comment for FREE RESOURCES ON AREA AND FORMULAE.

Step 2: 

Work out the area of the 20 cm diameter tin

Radius = diameter (20) ÷ 2 = 10 cm

Area = 3.14 × 10 × 10 = 314 cm²

Step 3: 

Work out the area of the 25 cm diameter tin

Radius = diameter (25) ÷ 2 = 12.5 cm

Area = 3.14 × 12.5 × 12.5 = 490.6 cm²

If you need any resources to build this "tricky" skill, drop me an email or leave a comment for FREE RESOURCES ON AREA AND FORMULAE.

Step 4: 

Compare the two areas

Larger tin area − smaller tin area

490.6 − 314 = 176.6 cm²

The 25 cm tin has a larger surface area.

Skills that Count Check

Why is this difference important?

Tin size affects depth and cooking time.

A bigger tin spreads the mixture thinner.

You may need more mixture or a shorter cooking time.

The Skills that Count

Understanding area helps you adapt recipes, avoid baking mistakes and work confidently with real-life measurements during Christmas cooking.

Diameter or Diametre, you may see either, but it refers to the measurement from one side of a circle to the other passing through the centre.

For YOUR FREE Circles explained resource, drop me a comment or email.