What size cake feeds 20 people?

A round 8-inch (20cm) cake feeds 20 with standard party portions (a ~2in/5cm-wide slice, roughly 80g each). A square 8-inch feeds about 26 of the same party portions, because a grid cut wastes less than wedges. If you serve smaller finger-style slices (around 1in wide, as at a wedding or afternoon tea), the same 8-inch round can stretch to roughly 24.

How many does a 10-inch cake serve?

A round 10-inch (25cm) cake serves approximately 30 guests on standard party portions (80-100g). A square 10-inch serves around 40 of the same party portions. Cutting smaller finger/wedding slices increases these counts by roughly 25-30%; cutting generous dessert slabs reduces them by 20-30%. The Portion Size input on this page changes the total cake weight estimate, not the recommended tin — drop down or up a size yourself if you prefer much smaller or larger slices.

When do I need a tiered cake?

For over 40 guests (round) or 54 guests (square) on party portions, a single tier becomes very large and awkward to bake and cut. Multi-tier cakes look impressive and are easier to manage. A 3-tier cake (6+8+10 inch round) serves about 60-65 party portions, since each tier’s servings simply add up.

Round or square cake - which is better value?

Square cakes serve more per size because a grid cut is more efficient than slicing wedges — about 25-30% more portions for the same width. On equal party portions an 8-inch square serves about 26 versus 20 for round. Round cakes are more traditional for celebrations, so choose on theme as well as 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

People to serve — one party slice each

Cake ShapeSquare yields ~25-30% more portions than round of the same width

Portion Size

Weight per slice (party slice ~80-100g) — sets the total weight estimate

How We Calculate This

This calculator recommends cake sizes based on guest count and shape, assuming one party portion per guest.

Standard portion size

A standard party cake portion is a slice roughly 5cm × 5cm (about 2" × 2") and 4-5cm tall, weighing around 80-100g. This is the dessert/celebration slice the portion table below is built on. A smaller finger or wedding slice (about 2.5cm/1" wide) yields roughly 25-30% more servings; a generous dessert slab yields fewer.

Party portions by size

Round: 6"=12, 8"=20, 10"=30, 12"=40
Square: 6"=16, 8"=26, 10"=40, 12"=54 (a grid cut yields ~25-30% more than round)
For larger numbers, multi-tier cakes are recommended — each tier’s portions add up

The Portion Size input adjusts the total cake weight estimate; the recommended tin is based on one standard party portion per guest.

Frequently Asked Questions

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Last updated: February 2026

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