Helium Balloon Calculator — Tank Size & Quantities

UK disposable canisters are rated by 9-inch balloons, but 11-inch balloons use about twice as much helium. A small canister fills roughly 30 × 9-inch (≈15 × 11-inch) balloons, a medium around 50 × 9-inch (≈25 × 11-inch), and a large about 100 × 9-inch (≈50 × 11-inch). Foil balloons use more helium per balloon — roughly 40% more than standard latex. Always buy slightly more capacity than you think you need.

Standard untreated 11-inch latex helium balloons float for around 12-18 hours indoors (about 12 hours minimum, longer in cool, climate-controlled rooms). Foil (mylar) balloons last 3-5 days. Using Hi-Float sealant can extend latex balloons to 24+ hours. Inflate latex balloons no more than 2-3 hours before the party for a fresh look. Foil balloons can be inflated the day before.

Disposable party canisters cost £20-£40 and fill 30-50 × 9-inch balloons (about 15-25 × 11-inch). Hiring a large refillable cylinder from a party shop costs £30-£60 and fills 100+ × 9-inch balloons. For more than about 25 × 11-inch balloons, hiring is usually better value. Under 20 balloons, buying them pre-filled from a party shop may be cheapest.

Helium balloons are safe but supervise young children. Deflated or burst balloons are a choking hazard for under-3s. Never let children inhale helium. Tie balloons securely to weights so they do not float away. Collect all balloon debris after the party.