Ordering the wrong amount of pizza is one of those small embarrassments that ruins a gathering. Too little and you're making a second order mid-party. Too much and you're eating cold pizza for a week. Here's how to get it right every time, with a calculator to do the work for you.
Most people guess. Some people Google "how many pizzas for 10 people" and read five contradictory forum answers. The reality is there's a reasonable formula, and it depends on a few factors β mostly the size of your pizzas, how hungry your crowd is, and what else is on the menu.
The basic rule of thumb
A standard working assumption is 3 slices per adult and 2 slices per child if pizza is the main event. At a typical Australian pizzeria, a large pizza (around 30β35cm diameter) gives you roughly 8 slices. A medium (around 25cm) gives you around 6 slices.
That means:
- 1 large pizza feeds roughly 2 adults or 2 adults + 1β2 small kids
- 3 large pizzas covers about 8β9 adults if pizza is the only main
- 5 large pizzas comfortably feeds a group of 12β14 mixed adults and kids
Skip the mental maths. Enter your group size, appetite level, and pizza size into our calculator and get an exact recommendation in seconds.
Open the Pizza Calculator πPizza sizes in Australia β what you're actually getting
Sizing varies between pizzerias, but here's what you're generally working with in Australia:
| Size | Approx. diameter | Slices | Best for |
|---|---|---|---|
| Small | 22β25 cm | 6 slices | Kids' portions, light sides |
| Medium | 28β30 cm | 8 slices | Couples, light adult appetite |
| Large | 33β36 cm | 8β10 slices | Standard adult main |
| Extra Large / Family | 40β45 cm | 12+ slices | Big groups, sharing platters |
What changes the calculation
1. Other food is being served
If you're serving pizza alongside salads, antipasto, garlic bread, or drinks, you can generally reduce your pizza estimate by 20β30%. People will fill up on sides and graze rather than eating full slices as their main.
2. Time of day matters
A pizza lunch gathering needs less than the same group at dinnertime. Lunch pizzas can go further β people are less hungry in the middle of the day.
3. The crowd's appetite
Teenagers eat more than retirees. A group of tradies after a big day eats more than a group of office workers. Adjust up if your group skews hungry, and down if it's a mixed group with kids and lighter eaters.
4. Pizza quality and variety
If you're ordering from a place with really good pizza, people tend to eat more β they want to finish it. Ordering two different varieties also tends to lead to more consumption than one option, because people want to try both.
A worked example
You're hosting 8 adults and 4 kids for a birthday dinner. Pizza is the main. The kids will eat less β let's say 2 slices each. The adults are hungry.
Kids: 4 Γ 2 = 8 slices needed β 1 large pizza covers this comfortably (10 slices per large).
Adults: 8 Γ 3 = 24 slices needed β 3 large pizzas gives you 30 slices, a bit of buffer.
Total: 4 large pizzas.
Plug the same numbers into our calculator and you'll get the same result, minus the head scratching.
Doing the maths for a group? Our pizza calculator handles appetite levels, kids vs adults, and different pizza sizes β no spreadsheet required.
Try the Pizza Calculator βCommon mistakes people make
Only ordering one type. Meat lovers vs vegetarian β if you're not sure about preferences, order a mix. One thing everyone agrees on isδΈεζ¬’ being stuck with the wrong pizza.
Forgetting to round up. If the math says 4.3 pizzas, order 5. Pizzas are much harder to rustle up at 7pm on a Saturday night than they are to put in the fridge for lunch tomorrow.
Not accounting for late arrivals. If your party has a stream of people arriving over a few hours, order for the peak headcount, not the count at any single moment.
Skipping the calculator. Most people are ordering for a fairly standard scenario. The calculator cuts through the guesswork in under a minute.
FAQs
How many pizzas for 20 adults at a party?
For hungry adults where pizza is the main: around 8 large pizzas. Divide 20 by 2.5 (the rough number of adults a large pizza feeds), round up, and you're there. For lighter appetites or if sides are involved, 6β7 large pizzas would cover it.
How many pizzas for 10 kids' birthday party?
Kids generally eat 2β3 slices each at a party. Assuming an average of 2.5 slices per child and a large pizza with 10 slices: 10 kids Γ 2.5 = 25 slices β 3 large pizzas. Order one extra if you want a comfortable buffer.
Is it cheaper to order large or medium pizzas?
Usually large pizzas give you more pizza per dollar, but it varies by pizzeria. One large pizza almost always costs less than two mediums and gives you roughly the same total surface area. Use our calculator to compare portions if you're unsure.
How do I estimate pizza for a mixed group of adults and kids?
Calculate adults and kids separately using 3 slices per adult and 2 per child, then add the totals. A large pizza typically gives you 8β10 slices, so divide your total slices needed by that to get how many larges to order. Our pizza calculator handles all of this automatically.
What's the best pizza to order for a group with different dietary requirements?
Order at least one vegetarian or plant-based option for every 3β4 meat-eating guests. Gluten-free bases are increasingly standard at most pizzerias. If someone is vegan, you'll need to check the base and toppings carefully β not all cheese alternatives are available everywhere.