How many calories in a slice of pizza? By size, base and topping

Pizza gets logged as "a slice," which is not a unit of anything. A slice from a 9 inch personal pizza is 55g. A slice from an 18 inch New York pie is 188g. Same word, three and a half times the food.

Here is what each one actually costs.

The quick answer

Classic-crust pizza is about 266 kcal per 100g. USDA reference data puts most cheese-and-tomato pizzas between 240 and 300 kcal per 100g depending on the base and the fat in the cheese.

So the only question that matters is how many grams a slice weighs. That comes from the diameter, and from how many pieces the box was cut into.

The size math nobody does

This is the single most useful thing on the page. Pizza is a circle, and the area of a circle scales with the square of the diameter. Going from a 12 inch to a 14 inch does not add 17% more pizza. It adds 36%.

Two 12 inch pizzas add up to 226 square inches. One 16 inch is 201. The two-for-one deal is more food than the upsize, and both are more food than anyone intended to buy.

The practical version: if you normally eat half a medium and you order a large instead, half is now 1,197 kcal rather than 851. The behaviour did not change. The number went up by 40%.

By base and topping

Everything below assumes the same 12 inch medium, cut into 8.

Two things fall out of that table.

Toppings matter less than the base. Swapping pepperoni for vegetables on a medium saves about 340 kcal across the whole pizza. Swapping deep pan for thin saves about 320 before you touch a topping. Doing both saves 660.

"Extra cheese" is not a small tick box. It is roughly 250 kcal on a medium, which is more than an extra slice. (For why cheese is the dense part, the cheese calorie breakdown has the per-type figures.)

Mozzarella is the reason pizza sits where it does. A 12 inch takes around 150g of it, which is about 420 kcal before the dough and oil. The base itself is roughly 250 kcal per 100g of dough, which is ordinary bread territory. (The bread calorie breakdown covers what that dough is doing on its own.)

Takeaway, supermarket, frozen, homemade

Same food, very different numbers, and the gap is mostly oil and cheese weight.

The finishing drizzle is the invisible part of restaurant pizza. A tablespoon of oil over the top is 119 kcal that appears nowhere on the menu. (The olive oil calorie breakdown covers how much a restaurant pour really is.)

The rest of the order

The pizza is usually not the problem. The order around it is.

The garlic and herb dip is the standout. It is 175 kcal in a pot the size of a shot glass, because it is essentially mayonnaise. Two pots is more than a slice of pizza.

A medium pepperoni with garlic bread, two dips and a 500ml cola is 1,907 + 260 + 350 + 210 = 2,727 kcal, which is a full day for most people in one sitting.

How to eat pizza inside a deficit

Pizza is not unusually calorie dense. At 2.7 kcal per gram it sits below cheese, nuts, chocolate and anything fried. What makes it hard is that it arrives as an undivided block with no obvious stopping point, and it is engineered to be eaten fast.

Four things that work, roughly in order of how much they save:

Decide the slice count before the box opens. Three slices of a medium is 639 kcal and a normal dinner. The decision is easy at the door and impossible at slice four.

Order one size down and add a salad. A small pepperoni plus a big undressed salad is around 1,200 kcal and fills more space than a medium alone. High-volume food is the lever here, and it is a large one. (High-volume low-calorie foods covers what actually works for this.)

Skip the dips, not the pizza. Two garlic and herb pots are 350 kcal of mayonnaise you would not have eaten with a spoon.

Bank calories earlier in the day, not the day before. A lighter, protein-heavy lunch makes a 900 kcal dinner fit without drama. Skipping breakfast to "save room" reliably backfires, because you arrive hungry and the box has no brakes.

NHS guidance on calories puts the average adult at 2,000 to 2,500 kcal a day. Three slices of a medium fits inside that without any special arrangement. The whole box does not. That is the entire distinction.

Pizza mistakes to avoid

Logging "one slice" without the diameter

The most common error on this food by a distance. A slice ranges from 133 to 466 kcal. Log the fraction of a known pizza instead: "half a 12 inch" is a real number, "two slices" is not.

Assuming thin crust is a diet pizza

It saves about 10 to 15%, which is worth having and is not transformative. A whole thin 14 inch is still around 2,100 kcal.

Treating the crust as free

The outer crust is 20 to 25% of the weight of a classic base pizza and the same 2.5 kcal per gram as the rest of the dough. Leaving the crusts genuinely saves 250 to 400 kcal on a medium. That is one of the few pizza hacks that is real.

Forgetting the saturated fat side of it

A medium pepperoni carries roughly 30g of saturated fat, most of a day's worth. American Heart Association guidance suggests keeping saturated fat to about 6% of calories for people managing cholesterol. That is a weekly-frequency argument, not a never argument.

Eyeballing the leftover

Cold pizza the next morning is the same 2.7 kcal per gram it was the night before. Two cold slices is 426 kcal, and it is almost never logged.

Three pizza orders that fit

The three-slice dinner (639 kcal)

• 3 slices of a 12 inch classic margherita (639 kcal)
• Large undressed side salad with vinegar (30 kcal)

Adds up to: 669 kcal. An ordinary dinner. The salad first is not a gimmick, it slows the first three minutes down, which is when most of the extra slices get eaten.

The homemade version you can predict (520 kcal)

• 1 shop-bought thin base, 12 inch (450 kcal for the whole base)
• 80g weighed mozzarella (240 kcal)
• Passata, herbs, vegetables (60 kcal)
• Half the pizza per person

Adds up to: 375 kcal per half, or 750 for the whole thing. Weighing the cheese is the entire trick. Most homemade pizzas fail because 200g of mozzarella goes on without anyone deciding to.

The half-and-salad split (851 kcal)

• Half a 12 inch pepperoni (954 kcal), minus the crusts (about 200 kcal saved)
• Big salad with 1 tsp olive oil and vinegar (80 kcal)

Adds up to: 834 kcal, in a meal that still involved pepperoni pizza on a Friday. (For where that number needs to sit in your week, how many calories to lose weight covers the arithmetic.)

The verdict

Pizza is 2.7 kcal per gram. A slice is meaningless without a diameter, a large is 36% more than a medium rather than a bit more, and the sides usually cost more than the extra slice you were worried about.

Weigh the box once. Once you know a medium is 1,700 kcal, deciding how much of it to eat becomes a normal decision instead of a guess.

Pairs well with: the cheese calorie breakdown, the bread calorie breakdown, and portion sizes without a scale.