Helium Balloon Calculator
Find out how many helium balloons it takes to float something. Enter the weight in ounces, grams, or pounds and pick a latex balloon size (9, 11, 12, or 36-inch) to get the balloon count, total helium in cubic feet and liters, and how it compares to a disposable party tank.
Example: with Weight to lift 4 · Weight unit ounces · Balloon size 11-inch latex (≈ 9.5 g lift) — standard → Balloons needed: 12 balloons (11-inch latex).
- Helium required4.8 cu ft of helium (136 L)
- Party-tank checkFits in one standard 8.9 cu ft party tank (a tank fills about 22 of this size)
- Lift per balloon≈ 9.5 g net lift per balloon (industry convention)
Computed by the calculator below using its default values. Change any input to see your own numbers.
Balloons = weight in grams ÷ net lift per balloon. The ≈ 9.5 g figure for an 11-inch latex balloon is the standard industry convention — helium lifts about 1 g per liter at sea level.
Where balloon lift comes from
A helium balloon floats for the same reason a boat does: it displaces something heavier than itself. At sea level and room temperature, air weighs about 1.20 g per liter and helium about 0.17 g, so every liter of helium inside a balloon can carry roughly 1 g. An 11-inch latex balloon holds about 11 liters, which buys ~11.5 g of gross lift; subtract the couple of grams the latex itself weighs and you land at the industry's working convention of ≈ 9.5 g of net lift.
Lift scales with volume — the cube of diameter — which is why a 36-inch balloon lifts not 3× but nearly 40× what an 11-inch does. When something heavy must fly, a few giants beat a hundred standards.
How it’s calculated
Balloons = weight in grams ÷ net lift per balloon, rounded up. Net lift per liter ≈ air density (1.20 g/L) − helium density (0.17 g/L) ≈ 1.03 g/L at sea level and 68°F; per-balloon values (5 g for 9-inch, 9.5 g for 11-inch, 12 g for 12-inch, 350 g for 36-inch latex) and fill volumes (0.25, 0.40, 0.52, 14.1 cu ft) are standard industry conventions. 1 oz = 28.35 g; 1 lb = 453.59 g; 1 cu ft = 28.32 L. Disposable party tanks hold 8.9 cu ft.
Sea-level values — lift drops roughly 3-4% per 1,000 ft of elevation, and latex balloons lose noticeable lift within 12-24 hours as helium diffuses out.
Latex balloon lift by size (conventions)
| Balloon | Helium fill | Net lift |
|---|---|---|
| 9-inch latex | 0.25 cu ft (7 L) | ≈ 5 g |
| 11-inch latex | 0.40 cu ft (11 L) | ≈ 9.5 g |
| 12-inch latex | 0.52 cu ft (15 L) | ≈ 12 g |
| 36-inch giant latex | 14.1 cu ft (400 L) | ≈ 350 g |
Industry filling guides; net lift ≈ 1 g per liter of helium minus balloon weight. Values are approximate conventions — real lift varies with inflation level and temperature.
Common mistakes
- Forgetting string and clips — ribbon and a clip can eat 1-3 g of every balloon's lift, a big fraction of a 9.5 g budget.
- Weighing in ounces and entering grams (or vice versa) — a 28× error in balloon count.
- Planning day-of lift for a day-before fill: plain latex sags overnight; hi-float treatment or foil balloons hold longer.
- Underfilling: a balloon blown to 9 inches instead of 11 loses about a third of its volume, and lift falls with it.
Frequently asked questions
What is the balloon lift formula?
Balloons needed = weight in grams ÷ net lift per balloon, rounded up. An 11-inch latex balloon lifts about 9.5 g by convention, so a 113 g (4 oz) item needs 12 balloons.
How many balloons would it take to lift a person?
A 150 lb person is about 68,000 g; at 9.5 g each that is roughly 7,200 standard 11-inch balloons — or about 195 of the 36-inch giants. Cluster ballooning is real, and really dangerous.
How many balloons does a party tank fill?
A standard disposable 8.9 cu ft helium tank fills about 22 eleven-inch balloons (0.40 cu ft each), or roughly 35 nine-inch balloons. Giant 36-inch balloons need more than a whole tank apiece.
Why does my foil balloon barely float?
Foil (mylar) balloons hold much less helium for their labeled size and the film is heavier than latex, so many 18-inch foils have only a few grams of spare lift. This calculator's presets cover latex.