Helium Tank Balloon Calculator

About this calculator

How many balloons a helium tank fills comes down to comparing volumes: the tank's total helium capacity divided by the volume one inflated balloon holds. A latex balloon is close enough to a sphere that its volume follows V = (4/3)πr³, so a 9-inch balloon (roughly 4.5-inch radius) holds noticeably less gas than an 11-inch balloon, and the difference compounds fast across dozens of balloons.

Party and event planners rely on this kind of calculation before buying a disposable helium tank, since tanks are sold by rated balloon count for a specific size — a common 14.9 cubic foot tank is typically marketed as filling around 50 nine-inch balloons or roughly 27 eleven-inch balloons, and mixing sizes without doing the math risks running out mid-setup. It is also useful for balloon arch and garland projects, where the total helium needed scales directly with balloon size and count.

Enter your tank's helium volume and the balloon diameter you plan to use, and the calculator estimates how many balloons the tank can fill.