How Much Pizza for a Party? (The 3/8 Rule)
Direct answer
About 8 large pizzas for 20 guests, using the reliable 3/8 rule: plan 3 slices per person, and a large pizza has 8 slices, so pizzas = (guests × 3) ÷ 8. For 20 that's 60 slices ÷ 8 ≈ 8 pizzas. Scale it to any headcount with the same formula. Adjust up for big eaters, teens, or pizza-only events with no sides; adjust down if it's one option among a spread. Order a mix including at least one plain cheese, and a couple extra for leftovers is rarely wasted.
One formula scales to any party
The 3/8 rule travels: (guests × 3) ÷ 8 = large pizzas, rounded up. 30 guests → ~11 pizzas; 50 → ~19. Then adjust for reality: a party of teenagers or a pizza-only event pushes toward 4 slices per person, while pizza as one item alongside a spread drops to 2. Confirm the shop's slices-per-pie (large is usually 8, but some cut 10) and swap that into the divisor. Always include a plain cheese for kids and picky eaters, and remember cold pizza is a feature, not waste.
Assumptions
- The 3/8 rule is published industry guidance (Instacart); appetites vary.
- Assumes a large 8-slice pizza — sizes and cuts differ by shop.
What changes this answer
- Appetite: teens and pizza-only events run toward 4 slices per person.
- Sides: with salad, wings or apps, drop toward 2 slices per person.
- Slice count: some shops cut 6 or 10 — adjust the formula's divisor.
Sources
- Instacart — pizza calculator — tier 3, verified 2026-07-23
Last checked 2026-07-22. Tiers: 1 government/regulator · 2 industry body · 3 official supplier docs · 4 large surveys · 5 professional material.