Cake Tin Size & Servings Calculator

Cake Serving and Tin Guide

How Many Servings from a Cake?

A standard 20cm round, 2-layer cake: 8-12 portions (dessert), 12-16 (afternoon tea), 16-24 (wedding/event finger portions). A 23cm round adds approximately 30% more volume than a 20cm — useful rule since area = π × r². A 25cm gives almost double the volume of a 20cm. For multi-tier wedding cakes, each tier is typically cut separately. Cutting guide: cut 20cm rounds in a grid rather than traditional wedge slices for more even portions — draw a circle 5cm from the edge and cut that ring into 5cm pieces, then cut the remaining centre into smaller wedges — this gives more consistent portion sizes than traditional wedge cutting from the middle out.

What's the difference between Round and Square Tin Equivalents?

A square tin holds approximately 25% more batter than a round tin of the same diameter. Rule: a 20cm square ≈ a 23cm round in terms of volume. Common equivalences: 15cm square = 18cm round. 18cm square = 20cm round. 20cm square = 23cm round. 25cm square = 28cm round. When a recipe specifies a round tin but you only have a square, use a tin approximately 2-3cm smaller. The baking time will change slightly (square tin bakes more evenly as the corners are closer to the heat).

What should I know about Scaling Recipes for Different Tin Sizes?

Volume scales with the square of the tin size (diameter squared for round tins, area for square/rectangular). Scaling factor = (new tin diameter)² / (original tin diameter)². Example: scaling from a 20cm to a 25cm round. Factor = 25²/20² = 625/400 = 1.5625. Multiply all ingredients by 1.56. Baking time: larger cakes need longer at a slightly lower temperature (reduce by 10-15°C and add 10-15 minutes). Always check with a skewer — the skewer should come out clean from the centre. Shallow tins bake faster than deep tins of the same diameter, since the batter is thinner and heat penetrates more quickly.

What should I know about Baking Temperature Adjustments?

Standard cake temperature: 160-180°C fan / 180-200°C conventional. For large cakes (above 25cm): reduce by 10-15°C to prevent overbrowning before the centre cooks. For small cup cakes (5cm): increase by 10°C and reduce time significantly (15-20 minutes vs 35-40 minutes for a standard round). Fan oven reduces temperature by approximately 20°C compared to conventional — if using a fan oven and the recipe specifies conventional, subtract 20°C. Altitude: above 1,000m, reduce baking powder by roughly 1/4 tsp per teaspoon called for, since lower air pressure makes cakes rise faster and can cause them to collapse if over-leavened.