Pizza size calculator
Enter each pizza's size and price, see which gives you more.
Is one 18-inch pizza more than two 12-inch pizzas?
Yes. An 18-inch pizza is π × 9² = 254.5 in², while two 12-inch pizzas are 2 × 113.1 = 226.2 in² — the single large pizza has more.
How much bigger is a 16-inch pizza than a 12-inch?
About 1.78 times: 201.1 in² against 113.1 in². Size is the diameter, but you eat the area, which grows with the square of the size.
How do I compare pizza prices?
Divide the price by the area to get the price per square inch. A 12-inch for $15 is 13.3¢ per in²; two 8-inch pizzas for $8 each are 15.9¢ — the 12-inch is the better deal.
How do I find the area of a pizza?
π × (diameter ÷ 2)². A 10-inch pizza is 78.5 in², a 14-inch 153.9 in² — almost twice as much pizza for 4 more inches.
Does a thicker crust change the comparison?
The calculator compares area, which is what you see on the plate. Two pizzas of the same size but different crusts have the same area — compare those by price alone.
What diameter gives twice the pizza of a 12-inch?
Area doubles when the diameter grows by the square root of 2, about 1.414. A 12-inch pizza is 113.1 in², and 17.0 inches gives 226.2 in², so a 17-inch pizza is nearly the same as two 12s.
How big is each slice?
Divide the area by the number of slices. An 18-inch pizza cut into 8 slices gives 31.8 in² per slice, which is more than a whole 6-inch pizza (28.3 in²).
Why area, not diameter
A pizza is a circle, and the amount of pizza is its area, A = π × (d ÷ 2)². Doubling the diameter quadruples the area, because the diameter is squared. That is why the step from a 10-inch to a 14-inch pizza (4 inches) nearly doubles the food, while the step from 14 to 18 inches adds a smaller share. Menu prices often rise more slowly than the area, so the larger size can cost less per square inch, but the calculator will tell you for the actual prices.
A worked comparison
Compare a 14-inch pizza at $17.50, two 10-inch pizzas at $10 each, and an 18-inch pizza at $22. The areas are 153.9, 157.1 (both together) and 254.5 in². The prices per square inch are 11.4¢, 12.7¢ and 8.6¢. The best deal is the 18-inch pizza. The calculator does this for any list, including a count for how many of each size you plan to buy.
Common mistakes
Comparing by diameter instead of area is the main one: a 16-inch pizza is 1.78 times a 12-inch, not 1.33 times. Entering the radius as the diameter is the second, and it cuts the area to a quarter. The comparison also assumes pizzas of the same style: a thick crust, extra toppings or a stuffed edge change what you are paying for, and a price per square inch does not capture that. Delivery fees and tax should be added to the price before you compare.
Sources: the area of a circle, A = πr², as in OpenStax Prealgebra 2e (chapter on geometry). Prices in the worked comparison are examples, not quotes. Related: circle calculator, unit price calculator, party food calculator and cake pan converter.