Free tool
Party Supply Calculator
Enter your guest list and party style. You get a shopping list with a small buffer, plus the reasoning behind each number.
How the numbers are worked out
Every quantity is a planning rule of thumb, rounded up, with a small buffer for the things that always go wrong at parties: a crushed hat, a popped balloon, cups that get abandoned half full.
| Item | Rule used | Why |
|---|---|---|
| Party hats | One per wearer + 10%, plus one | Hats get sat on and traded; spares avoid tears |
| Balloons | 1, 2 or 3 per guest by decor style | Simple = a few clusters; all-out = garland plus clusters |
| Banner length | 8 / 16 / 30 ft by style | One wall, two focal points, or wrap-around |
| Plates | 1.5 per guest | Food and cake |
| Cups | 2 per guest (3 for 3+ hours) | Guests lose track of cups |
| Napkins | 3 per guest | Food, cake and spills |
Kids’ parties under two hours rarely need more cups than the calculator shows. Outdoor parties usually need more napkins and fewer balloons (wind and heat are hard on latex).
Turn the list into a plan
Hats come in packs of about 11–12, so round up to whole packs — see how many party hats you need for counts by guest list and party hat sizes if you have toddlers or adults. For balloons, decide between latex clusters and a few large foil shapes with foil vs latex balloons. Then shop party hats and crowns and balloons.