Small Pizzas in a Large Calculator
Find how many small pizzas (or pies) equal one large by comparing their round areas — the honest way to size a group order.
How it works
Equivalent smalls = (large diameter ÷ small diameter)²
Because a round pizza’s area is proportional to the square of its diameter, the number of small pizzas that equal a large one is the diameter ratio squared — not the plain ratio. An 18-inch pizza against a 10-inch one is not 1.8 smalls but (18/10)² = 3.24 smalls. This is why two smalls almost never match one large.
Worked example
An 18-inch large has area π × 9² = 254.5 in²; a 10-inch small has π × 5² = 78.5 in². The large equals 254.5 ÷ 78.5 = 3.24 smalls, the same as (18 ÷ 10)² = 3.24. To match one large you’d need to buy 4 smalls.
Sources: Area of a circle — Wikipedia
Frequently asked questions
Do two medium pizzas equal one large?
Rarely. Area scales with the diameter squared, so two 12-inch pizzas (2 × 113 = 226 in²) fall short of one 16-inch (201 in²)... actually exceed it here, but two 10-inch (157 in²) are well short of one 16-inch (201 in²). Always compare squared diameters.
Why square the diameter ratio?
Area = π × radius², and radius is half the diameter, so area is proportional to diameter². Dividing two areas leaves the diameter ratio squared, which is why a modest size bump changes the count a lot.
Should I round up or down?
Round up if you want at least as much pizza as the large. The exact ratio tells you the true equivalence; the rounded-up count tells you how many whole smalls to actually order.
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This calculator is for educational purposes. Double-check important results before acting on them.