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Helium Tank Balloon Calculator

Enter your tank's helium volume and balloon size to see how many balloons it fills.

How it is calculated

You enter the helium volume of the tank in cubic feet and choose one of three latex balloon sizes. The tool uses a fixed amount of helium per balloon: 0.25 ft³ for a 9-inch balloon, 0.50 ft³ for 11-inch and 0.65 ft³ for 12-inch. The count is balloons = floor(tank ÷ helium per balloon), always rounded down because a part-filled balloon does not float well. The tank volume must be above zero. These per-balloon figures are the tool's assumptions for ordinary latex balloons; foil balloons, other sizes and the extra gas needed for higher float time are not covered, and a tank's rated capacity may differ from the label of a particular brand.

Worked example

A tank holding 14.9 ft³ of helium, filling 12-inch balloons at 0.65 ft³ each. Dividing 14.9 ÷ 0.65 gives 22.9. Rounded down, the tank fills 22 balloons. With 11-inch balloons (0.50 ft³) the same tank gives 29 balloons, and with 9-inch balloons (0.25 ft³) it gives 59, so the size you pick changes the count a lot.

Try this example →

Common mistakes

  • Entering the tank's weight, its price or its pressure instead of the helium volume in cubic feet. The tool works only from the volume printed on the tank.
  • Picking the balloon size from the package rather than the size you will inflate to. The calculator assumes a full inflation to that diameter, so under-filling stretches the count.
  • Mixing sizes in one job and calculating each with the full tank. Work out the share of the tank each size uses, or run the larger size first and use the remainder.
  • Planning to the exact number. It is rounded down and ignores gas lost in filling, so keep a few balloons' worth in reserve.
  • Using the result for foil balloons or very large latex balloons. Only 9-, 11- and 12-inch latex are offered.

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. This calculator uses typical helium per balloon instead: 0.25 ft³ (9-inch), 0.50 ft³ (11-inch), 0.65 ft³ (12-inch).

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 (this calculator gives about 59 and 29), 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.

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