Pizza Calculator
Count the adults and kids, pick the appetite and the pizza size, and get how many to order with slices to spare. Then compare two prices per square inch.
light 2, normal 3, hungry 4 slices per adult; kids 2
Order
4 large pizzas
38 slices needed, 2 spare
Per person
44 sq in
pizza area each, spare included
Rule of thumb
3 / 8 rule
3 slices per adult, 8 slices per large
Same crowd, every size
| Size | Slices each | Area (sq in) | Pizzas to order | Spare slices |
|---|---|---|---|---|
| Small (10") | 6 | 79 | 7 | 4 |
| Medium (12") | 8 | 113 | 5 | 2 |
| Large (14") | 10 | 154 | 4 | 2 |
| Extra large (16") | 12 | 201 | 4 | 10 |
| Party (18") | 12 | 254 | 4 | 10 |
Which is the better deal?
A: 12"
11.5¢ / sq in
113 sq in for $12.99
B: 16"
9.4¢ / sq in
201 sq in for $18.99
Verdict
B wins
one 16" = 1.78 × the 12"
Area = π × (diameter ÷ 2)². Doubling the diameter quadruples the pizza, which is why one 16-inch is 1.78 twelve-inch pizzas and almost always cheaper per square inch than two mediums.
Pizzas to order, adults only, normal appetite
| People | Slices | 10" (6 sl) | 12" (8 sl) | 14" (10 sl) | 16" (12 sl) | 18" (12 sl) |
|---|---|---|---|---|---|---|
| 4 | 12 | 2 | 2 | 2 | 1 | 1 |
| 6 | 18 | 3 | 3 | 2 | 2 | 2 |
| 8 | 24 | 4 | 3 | 3 | 2 | 2 |
| 10 | 30 | 5 | 4 | 3 | 3 | 3 |
| 12 | 36 | 6 | 5 | 4 | 3 | 3 |
| 15 | 45 | 8 | 6 | 5 | 4 | 4 |
| 20 | 60 | 10 | 8 | 6 | 5 | 5 |
| 25 | 75 | 13 | 10 | 8 | 7 | 7 |
| 30 | 90 | 15 | 12 | 9 | 8 | 8 |
| 40 | 120 | 20 | 15 | 12 | 10 | 10 |
| 50 | 150 | 25 | 19 | 15 | 13 | 13 |
Size, area and how many 12-inch pizzas it equals
| Diameter | Area (sq in) | = 12-inch pizzas | Usual slices | Sq in per slice |
|---|---|---|---|---|
| 8" | 50 | 0.44 | 4 | 13 |
| 10" | 79 | 0.69 | 6 | 13 |
| 12" | 113 | 1 | 8 | 14 |
| 14" | 154 | 1.36 | 10 | 15 |
| 16" | 201 | 1.78 | 12 | 17 |
| 18" | 254 | 2.25 | 12 | 21 |
| 20" | 314 | 2.78 | 12 | 26 |
| 24" | 452 | 4 | 12 | 38 |
Ordering tips that survive contact with a party: round up, because leftover pizza is not a problem; keep half the order plain cheese or pepperoni; get one vegetarian per ten guests; and if the shop offers an 18-inch, it is usually the cheapest square inch on the menu.
Frequently Asked Questions
How many pizzas do I need per person?
Plan three slices per adult and two per child when pizza is the meal, then divide by the slices per pizza (8 for a 14-inch large at most chains). Ten adults and four kids need 38 slices, which is five larges. Add a slice per adult for teenagers, game day or a late night, and drop one when there is other food.
How many pizzas for 20 people?
Twenty adults at three slices each is 60 slices, which is 8 large 14-inch pizzas at 8 slices, or 5 extra-large 18-inch pizzas cut into 12. For a mixed crowd of 15 adults and 5 kids it is 55 slices, so 7 larges. Order two-thirds cheese and pepperoni and the rest specialty.
How many slices are in a large pizza?
Eight at most US chains for a 14-inch large; ten for a 16-inch extra large; twelve for an 18-inch. Sizes and slice counts vary by shop, so the calculator lets you set both. A slice of a 16-inch is 36% bigger than a slice of a 14-inch, which matters when you count in slices.
Is a large pizza a better deal than two mediums?
Almost always. Area grows with the square of the diameter: a 16-inch pizza is 201 square inches, a 12-inch is 113, so one 16 is 1.78 twelves. If the large costs less than 1.78 times the medium, it wins. The price comparison above computes cents per square inch for any two sizes.
How much pizza is in a square inch?
Not much on its own, but per person it is the fair comparison. A hungry adult eats about 40-45 square inches (three slices of a 14-inch); a child about 25. The calculator shows square inches per person for your order so you can see whether the spare slices are generous or thin.
These tools use baker's percentages, salt-by-weight brining, coffee ratios by weight and the USDA roasting and thawing tables, all stated on each page. They are starting points for your kitchen, your flour and your oven: taste the brine, watch the dough, and always cook poultry to 165°F on a thermometer.