Pizza Size Calculator
Is the large really better value? Enter the size and price of each pizza and see the price per square inch, which wins and by how much. Advanced adds 2-for-1 orders, square pizzas, crust, slices and how many to order.
How your pizza value is worked out
Price per area = what you pay ÷ how much pizza you get. Area grows with the square of the size.
- 1
Measure across
Large: 18" roundMedium: 12" roundhalf = 9 and 6
- 2
Work out the area
π × 9² = 254.47π × 6² = 113.10sq in
- 3
Price per sq in
18.00 ÷ 254.47= 0.070710.00 ÷ 113.10= 0.0884
- 4
The better value
Large wins20% cheaper25% more pizza
Read more: the formula, worked example and pizza size tables
The formula
area of a round pizza = π × (size across ÷ 2)²
area of a rectangle = length × width
topping area (with a crust) = π × (half the size − crust)², or (length − 2 × crust) × (width − 2 × crust)
price per square inch = (price × how many) ÷ (area × how many)
% cheaper = (1 − best price per area ÷ worst price per area) × 100
% more pizza = (worst price per area ÷ best price per area − 1) × 100
one big = (big area ÷ small area) small pizzas
pizzas to order = people × slices each ÷ slices in one, rounded up
Worked example
A medium 12-inch pizza costs 10.00 and a large 18-inch pizza costs 18.00.
- Medium: half of 12 is 6, so the area is π × 6² = 36π = 113.10 sq in. 10.00 ÷ 113.10 = 0.0884 a sq in.
- Large: half of 18 is 9, so the area is π × 9² = 81π = 254.47 sq in. 18.00 ÷ 254.47 = 0.0707 a sq in.
- The large is better value: 1 − 0.0707 ÷ 0.0884 = 1 − 0.8 = 20% cheaper per square inch. The other way round, 0.0884 ÷ 0.0707 = 1.25, so you get 25% more pizza for your money.
- One 18-inch pizza = 81π ÷ 36π = 2.25 twelve-inch pizzas. The medium would have to cost 18.00 ÷ 2.25 = 8.00 to be as good.
- Per 100 cm²: 113.10 sq in × 6.4516 = 729.66 cm², so the medium is 10.00 ÷ 7.2966 = 1.37 per 100 cm²; the large is 1,641.73 cm², so 18.00 ÷ 16.4173 = 1.10 per 100 cm².
In Advanced, with slices: the medium is cut into 8 (14.14 sq in and 1.25 a slice) and the large into 12 (21.21 sq in and 1.50 a slice). For 6 people at 3 slices each you need 18 slices: 18 ÷ 8 = 2.25, so 3 mediums for 30.00, or 18 ÷ 12 = 1.5, so 2 larges for 36.00. The larges cost more but give 508.94 sq in against 339.29 sq in, and 6 spare slices.
With a 1-inch crust only the middle counts: the medium has π × 5² = 78.54 sq in of topping and the large π × 8² = 201.06 sq in. The large is then 1 − (18 ÷ 64) ÷ (10 ÷ 25) = 29.69% cheaper per square inch of topping.
Pizza sizes compared
| Size | Area | Same as |
|---|---|---|
| 8 in (20.3 cm) | 50.27 sq in | 0.44 × 12-inch |
| 10 in (25.4 cm) | 78.54 sq in | 0.69 × 12-inch |
| 12 in (30.5 cm) | 113.10 sq in | 1 × 12-inch |
| 14 in (35.6 cm) | 153.94 sq in | 1.36 × 12-inch |
| 16 in (40.6 cm) | 201.06 sq in | 1.78 × 12-inch |
| 18 in (45.7 cm) | 254.47 sq in | 2.25 × 12-inch |
Tips for ordering
- Doubling the size gives four times the pizza: a 16-inch has 4 times the area of an 8-inch.
- "Two mediums" deals often sound bigger than one large but hold less pizza. Set "How many" to 2 in Advanced to check.
- Menus name sizes differently ("medium" can be 10 to 14 inches), so compare the size across, not the name.
- Slices each is only a guess: about 2 for children, 3 for most adults and 4 or more for big eaters.
Common questions
Is a bigger pizza better value?
Usually, because the area grows with the square of the size. An 18-inch pizza is 1.5 times as wide as a 12-inch, but has 1.5² = 2.25 times as much pizza. If the 12-inch costs 10.00 and the 18-inch 18.00, the large is 20% cheaper per square inch, so you get 25% more pizza for your money.
How many 12-inch pizzas make an 18-inch pizza?
One 18-inch pizza has the same area as 2.25 twelve-inch pizzas. Divide the two sizes and square the answer: (18 ÷ 12)² = 1.5² = 2.25. Two 12-inch pizzas (226.19 sq in) are less pizza than one 18-inch (254.47 sq in).
How do I work out the area of a pizza?
Halve the width to get the radius, square it and multiply by pi (3.14159). A 12-inch pizza is π × 6 × 6 = 113.10 square inches. For a rectangular pizza, multiply the length by the width: 16 × 12 inches is 192 square inches.
Does the crust change which pizza is better value?
Yes. The crust is about the same width on every size, so it takes a bigger share of a small pizza. With a 1-inch crust, 31% of a 12-inch pizza is crust but only 21% of an 18-inch. Add a crust width in Advanced to compare only the part with toppings.
How many pizzas do I need for a party?
A rough guess is 3 slices each for adults, fewer for small children and more for big eaters. 6 people × 3 slices = 18 slices, which is 3 pizzas cut into 8 slices, or 2 pizzas cut into 12. Change the slices each in Advanced to suit your group.
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