How many pizzas do I need?
Enter how many people are eating, how many slices each, and the pizza size. The pizza calculator tells you how many pizzas to order and what they cost.
- Pizzas to order
- 4
For 10 people eating 3 slices each, order 4 pizzas.
- Slices needed
- 30
- Slices left over
- 2
- Area of one pizzain²
- 153.9
- Area of one pizza (cm²)cm²
- 993.1
- Pizza per personin²
- 61.6
- Total cost
- $60.00
- Cost per person
- $6.00
- Price per square inch
- $0.0974
- Size ratio
- 1.96
Pizzas to order: 4. For 10 people eating 3 slices each, order 4 pizzas.
How to calculate
Works out how many pizzas to order for a group from the people, the slices each person eats and the slices per pizza, with the cost, the price per square inch and which of two sizes is the better deal.
Example with the default inputs (People 10, Slices per person 3, Slices per pizza 8, Pizza size 14 in, Price per pizza $15.00, Other size 10 in): For 10 people eating 3 slices each, order 4 pizzas.
Method: pizzas = ⌈people × slices per person ÷ slices per pizza⌉; area = π × (d ÷ 2)²; price per in² = price ÷ area.
- Pizzas are round and every slice is eaten by someone; there is no extra pizza for big eaters.
- Prices are what you type; the page fetches no menus or prices.
- Sizes from 1 to 100 in (2.54 to 254 cm) across.
Worked examples
Each example is checked against the calculator on every build.
- People 10, Slices per person 3, Slices per pizza 8, Pizza size 14 in, Price per pizza $15.00 gives Pizzas to order 4, Slices needed 30, Slices left over 2, Area of one pizza 153.93804, Total cost $60.00, Cost per person $6.00, Price per square inch $0.10.Source: OpenStax, Prealgebra 2e, §9.5 Solve Geometry Applications: Circles and Irregular Figures, area of a circle A = πr² (https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures, retrieved 2026-10-02)
- People 6, Slices per person 2.5, Slices per pizza 6, Pizza size 11.81 in, Price per pizza $12.00, Other size 15.75 in, Price of the other size $20.00 gives Pizzas to order 3, Slices left over 3, Size ratio 0.5625, Better deal The other size costs less per square inch.Source: OpenStax, Prealgebra 2e, §9.5 Solve Geometry Applications: Circles and Irregular Figures, area of a circle A = πr² (https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures, retrieved 2026-10-02); NIST SP 811 Appendix B: 1 in = 2.54 cm exactly (https://www.nist.gov/pml/special-publication-811, retrieved 2026-10-02)
- People 4, Slices per person 2, Slices per pizza 8, Pizza size 16 in, Price per pizza $18.00, Other size 8 in, Price of the other size $4.50 gives Pizzas to order 1, Slices left over 0, Size ratio 4, Better deal Both sizes cost the same per square inch.Source: OpenStax, Prealgebra 2e, §9.5 Solve Geometry Applications: Circles and Irregular Figures, area of a circle A = πr² (https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures, retrieved 2026-10-02)
How it works
- Slices needed = people × slices per person.
- Pizzas to order = slices needed ÷ slices per pizza, rounded up to a whole pizza.
- Slices left over = pizzas × slices per pizza − slices needed.
- Area of one pizza = π × (d ÷ 2)², with d the diameter in inches, in square inches; in square centimetres it is that × 6.4516.
- Pizza per person = pizzas × area ÷ people, in square inches.
- With a price per pizza: total cost = pizzas × price, cost per person = total cost ÷ people, and price per square inch = price ÷ area.
- With another size: size ratio = (d ÷ d₂)², how many of the other size make one of yours. With both prices, the better deal is the size with the lower price per square inch, and the other size’s price per square inch is shown.
Counts, slices, the cost and the size ratio are exact: each typed number is read as the exact decimal you typed (a size in cm is divided by exactly 2.54). The better deal is decided exactly by comparing price × (other diameter)² with other price × diameter² (π cancels), so equal prices per square inch say "Both sizes cost the same per square inch". Areas use π and are shown to 0.1; prices per square inch to $0.0001; money to the cent, rounded half up.
Rules
- 1 to 100,000 people; 0.5 to 50 slices per person; 1 to 64 slices per pizza; sizes from 1 to 100 inches (2.54 to 254 cm); prices from $0 to $10,000.
Worked examples by hand
10 people, 3 slices each, 14-inch pizzas cut in 8, $15 each. Slices needed = 10 × 3 = 30. 30 ÷ 8 = 3.75, so 4 pizzas, with 4 × 8 − 30 = 2 slices left over. Area = π × 7² = 153.9 in². Total cost = 4 × 15 = $60, or $6 per person. Price per square inch = 15 ÷ 153.938 = $0.0974.
6 people, 2.5 slices each, 30 cm pizzas cut in 6 at $12, against 40 cm at $20. 6 × 2.5 = 15 slices; 15 ÷ 6 = 2.5, so 3 pizzas and 3 slices spare. Size ratio = (30 ÷ 40)² = 0.5625. Compare 12 × 40² = 19,200 with 20 × 30² = 18,000: the 40 cm pizza costs less per square inch, so the other size is the better deal.
4 people, 2 slices each, a 16-inch pizza at $18 against 8-inch pizzas at $4.50. 8 slices, so 1 pizza and 0 spare. Ratio (16 ÷ 8)² = 4. 18 × 8² = 1,152 and 4.5 × 16² = 1,152: both sizes cost the same per square inch.
Other questions people ask
How many pizzas do I need for 10 people?
At 3 slices each and 8 slices per pizza, 10 people need 30 slices: 30 ÷ 8 = 3.75, so order 4 pizzas. You will have 2 slices left over.
How many slices are in a pizza?
It depends on the shop and the size. Many cut a 12-inch to 14-inch pizza into 8 slices and a 16-inch into 8 to 12. Type the number your shop uses.
Is one large pizza a better deal than two mediums?
Often, because the area grows with the square of the width. A 16-inch pizza has (16 ÷ 8)² = 4 times the area of an 8-inch pizza, not twice. Compare the price per square inch: the lower one is the better deal.
How do I find the area of a pizza?
Halve the diameter to get the radius r, then area = π × r². A 14-inch pizza has r = 7 in, so its area is π × 49 ≈ 153.9 square inches.
How many calories are in pizza?
USDA FoodData Central lists frozen cheese pizza, cooked, at 268 kcal per 100 g. A slice’s calories depend on its weight and toppings, so weigh a slice or check the shop’s nutrition facts.
Does the calculator use real menu prices?
No. Type the prices from your shop’s menu. The page makes no requests for prices.