Pizza Size Calculator
Compare pizza sizes by actual surface area, two 12-inch pizzas vs one 18-inch is not the obvious answer. Quick math for ordering and value comparison.
Last updated: May 2026
Enter two diameters to compare surface area.
Why pizza size matters more than you think
Pizza area scales with the square of the radius, not the diameter, so a small increase in diameter has a large effect on total food. A 40 cm pizza has π × 20² = 1,257 cm². Two 28 cm pizzas together have 2 × π × 14² = 1,232 cm². The single large pizza has more area than two mediums, even though its 40 cm diameter looks smaller than two 28 cm pizzas combined (56 cm). This is why the large pizza is almost always better value per euro.
Adding 5 cm to a 30 cm pizza (to 35 cm) increases area by 36%. Adding the same 5 cm to a 20 cm pizza increases area by 56%. The effect of diameter is non-linear, which is the entire point of this calculator.
Standard pizza sizes: inch, cm and area
Most pizzerias state size in inches. The table below shows the exact diameter in centimetres and the actual surface area, which is the figure that determines how much pizza you get per euro.
| Name | Diameter (inch) | Diameter (cm) | Area (cm²) | Typical serves |
|---|---|---|---|---|
| Personal | 10" | 25 cm | 507 cm² | 1 person |
| Small | 12" | 30 cm | 730 cm² | 1-2 persons |
| Medium | 14" | 36 cm | 994 cm² | 2-3 persons |
| Large | 16" | 41 cm | 1,297 cm² | 3-4 persons |
| Extra large | 18" | 46 cm | 1,642 cm² | 4-6 persons |
The jump from 16" to 18" adds 345 cm² (27% more area) for what looks like a modest 2-inch increase in diameter. A 12" and 14" side-by-side look similar, but the 14" has 36% more pizza.
Frequently Asked Questions
Is a large pizza better value than two smalls?
Almost always yes. A 40 cm pizza has 1,257 cm² of area. Two 28 cm pizzas together total 1,232 cm², slightly less than a single 40 cm. The large pizza wins on area and typically costs less per cm². The exception is when the smaller pizzas have different toppings, which changes the comparison to preference rather than area.
Why does diameter matter more than people expect?
Area = π × radius². Radius is half the diameter, so doubling the diameter quadruples the area. A 5 cm increase on a 30 cm base adds 36% more surface. Most people estimate pizza size linearly (bigger diameter = proportionally more food), which underestimates the actual difference by a large margin.
What is a 12-inch or 14-inch pizza in centimetres?
12 inches = 30.5 cm; 14 inches = 35.6 cm; 16 inches = 40.6 cm. Enter the converted value directly in centimetres. A 12" pizza has about 730 cm² of area; a 14" has about 995 cm², 36% more for a modest-looking 2-inch difference in diameter.