How Much Pizza Should I Order?

Plan a group order or compare pizza deals using actual pizza area—not inconsistent slice counts.

Your inputs stay in your browser. Entries are never uploaded.

Who are you feeding?

Appetite

Choose a practical estimate; portions vary.

Advanced Settings
sq in
% of adult

What pizza sizes are available?

Choose the sizes your restaurant actually sells. Enable every size you want the calculator to consider, then enter its real diameter—or width and length for a sheet pizza.

Restaurant labels vary, so measurements determine the recommendation. Add prices only if you want a cheapest-option comparison.

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Your pizza plan

Why pizza size matters

Pizza area grows with the square of its radius. A 12-inch pizza has an area of π × 6², or about 113 square inches. An 18-inch pizza has an area of π × 9², or about 254 square inches. Although its diameter is only 50% larger, the 18-inch pizza contains more than twice as much pizza.

For rectangular sheet pizzas, the calculator multiplies width by length. “Half sheet” and “full sheet” labels are not standardized between restaurants, so use the restaurant’s actual dimensions whenever possible. The included 13 × 18 and 18 × 26 defaults are editable examples.

Common pizza size reference

SizeApproximate area
10-inch round78.5 sq in
12-inch round113.1 sq in
14-inch round153.9 sq in
16-inch round201.1 sq in
18-inch round254.5 sq in
13 × 18-inch sheet234 sq in
18 × 26-inch sheet468 sq in

Round values use area = π × (diameter ÷ 2)². Sheet values use area = width × length.

Frequently Asked Questions

It depends on pizza diameter and appetite. This calculator estimates each person's pizza area instead of relying on inconsistent slice sizes.

Two to three slices is a common rule of thumb, but slice size varies substantially with pizza diameter and how the restaurant cuts it.

Using the calculator's average appetite, some sides, a little extra, and 14-inch pizzas, 10 adults need about four pizzas.

Using the average assumptions, some sides, a little extra, and 14-inch pizzas, 20 adults need about seven pizzas.

It depends on actual diameters. One 18-inch pizza is about 254 square inches, while two 12-inch pizzas total about 226 square inches, so the 18-inch pizza provides about 12.5 percent more.

Pizza is two-dimensional. Area accounts for the way pizza amount grows with the square of its radius, while diameter or slice count alone can mislead.

The calculator starts by estimating a child eats 60 percent of the adult amount. Adjust appetite based on children's ages and the other food being served.

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