Pizza Size Calculator
Enter the diameter and price of two pizzas and this calculator tells you which is the better deal. It works out the actual surface area of each pizza, the price per square inch (or square centimetre), and how much edible topping area you get if you account for the crust. You can also find the break-even price at which both pizzas cost the same per unit of area. Switch freely between metric and imperial.
Why pizza size matters more than you think
A pizza is a circle, and area grows with the square of the radius. This means a 14-inch pizza is not 40% bigger than a 10-inch pizza; it is nearly 96% bigger. A 16-inch pizza has more than 2.5 times the area of a 10-inch one. Because menus list diameters, not areas, our intuition about size differences is systematically wrong. That is why a "large" pizza at a reasonable price almost always beats two "small" ones, even when the headline price gap looks modest. This calculator makes the comparison precise.
How price-per-square-inch works
The true cost comparison divides each pizza's price by its actual circular area: Price per sq in = Price / (pi x (diameter / 2)^2). The pizza with the lower cost-per-area gives you more food per dollar regardless of the raw price. Because the area grows quadratically, even a small increase in diameter can deliver a large jump in value. For example, a 14-inch pizza at $14 costs $0.065 per sq in, while a 10-inch pizza at $8 costs $0.102 per sq in, meaning the large pizza is about 57% better value despite looking nearly twice as expensive at checkout.
What the crust offset does
Not everyone eats the crust. When you select a crust thickness, the calculator subtracts a ring of that width from both edges to find the "topping area": the part that actually has sauce and toppings. A 14-inch pizza with a 1-inch regular crust becomes a 12-inch topping circle with an area of about 113 sq in instead of 154 sq in. This can shift the value verdict, particularly when comparing a thin-crust pizza with a generous topping spread against a deep-dish pie where most of the edge is bread.
The break-even price and how to use it at the counter
The break-even price tells you the exact price Pizza B would need to be for it to match Pizza A in cost-per-area. If the displayed menu price of Pizza B is below the break-even figure, it is the better deal; if it is above, Pizza A wins. You can use this in real time: type in both diameters, set Pizza A price to whatever the small costs, set Pizza B price to whatever the large costs, and read off whether the large is worth the upgrade. The savings percentage tells you by how much.
Common pizza sizes and their areas
| Size label | Diameter (in) | Total area (sq in) | Slices (typical) |
|---|---|---|---|
| Personal | 6 | 28.3 | 4 |
| Small | 8 | 50.3 | 6 |
| Small | 10 | 78.5 | 6 |
| Medium | 12 | 113.1 | 8 |
| Medium | 14 | 153.9 | 8 |
| Large | 16 | 201.1 | 10 |
| Extra-large | 18 | 254.5 | 12 |
| Extra-large | 20 | 314.2 | 12 |
Standard US pizza size labels with approximate diameters and full circular areas. Actual areas vary by pizzeria.
Frequently asked questions
Is a large pizza always better value than two smalls?
Almost always, yes. Because pizza area grows with the square of the radius, doubling the diameter would give four times the area. In practice, a 16-inch pizza typically contains more total area than two 10-inch pizzas, yet usually costs less in total. Use this calculator with the exact prices from your menu to confirm, because there are occasional promotions where two smalls genuinely win.
How do I convert a pizza diameter to area?
Use the circle area formula: area = pi x radius squared, where radius = diameter / 2. For a 12-inch pizza, the radius is 6 inches, so the area is pi x 36, which is about 113.1 square inches. For a 14-inch pizza the area is pi x 49, about 153.9 sq in. The key insight is that a 14-inch pizza is 36% larger in diameter but 36% larger in area too, not 36% larger in area: it is actually about 36% more area because area = pi x r^2 and r goes from 6 to 7.
What counts as a standard pizza size?
Sizing labels vary by country and chain. In the United States, a common convention is: personal around 6 inches, small around 8-10 inches, medium around 12-14 inches, large around 16 inches, and extra-large 18 inches and above. New York-style pies often run 18 inches, while Neapolitan pizzas are traditionally capped at 35 centimetres (about 13.8 inches) by the official Associazione Verace Pizza Napoletana standards. Always use the actual diameter from the menu rather than the size label.
Does the shape of the pizza matter for this calculation?
This calculator assumes a circular pizza. Square or rectangular pizzas (Sicilian, Detroit-style, grandma pies) should be calculated with length x width instead. If you have a rectangular pizza, multiply its length by its width to get the area, then divide the price by that area to find cost per square inch.
How much pizza should I order per person?
A common rule of thumb is 2 to 3 slices per adult for a normal appetite, with a standard large pizza cut into 8 slices feeding 3 to 4 adults. For a party with a mix of adults and children, plan on roughly 2.5 slices per person on average. Once you know how many slices you need, use the area comparison here to find the most cost-effective way to hit that total.