What size cake feeds 20 people?

A round 8-inch (20cm) cake feeds 20 with standard party portions (80g each). A square 8-inch feeds about 32 due to more efficient cutting. For coffee-sized portions (smaller slices), an 8-inch round can stretch to 24.

How many does a 10-inch cake serve?

A round 10-inch (25cm) cake serves approximately 30 guests. A square 10-inch serves around 50 guests. These assume standard 80-100g party portions. For larger dessert-style slices, reduce by 20-30%.

When do I need a tiered cake?

For over 40 guests (round) or 72 guests (square), a single tier is very large and difficult to manage. Multi-tier cakes look impressive and are practical. A 3-tier cake (6+8+10 inch) serves about 60-65 people.

Round or square cake - which is better value?

Square cakes serve more per size because you cut a more efficient grid pattern. An 8-inch square serves 32 vs 20 for round. However, round cakes are more traditional for celebrations. Choose based on your theme and guest count.

PartyCalcs

Cake Size Calculator — Right Size for Your Guests

Choose the right cake size and tiers for your number of guests.

Number of Guests

Cake Shape

Portion Size

How We Calculate This

This calculator recommends cake sizes based on guest count and shape.

Standard portion size

A standard party cake portion is approximately 2.5cm wide x 5cm tall (1" x 2"), weighing about 80g. This is a generous finger-width slice ideal for celebrations.

Portions by size

Round: 6"=12, 8"=20, 10"=30, 12"=40
Square: 6"=18, 8"=32, 10"=50, 12"=72
For larger numbers, multi-tier cakes are recommended

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Adjust quantities based on your guests and event type.