Helium Balloons Calculator
Use this calculator in two ways: find how many helium balloons you need to lift an object (a person, a gift, a pet), or find how many balloons you can inflate from a helium tank for a party. Pick a balloon size, enter your weight or tank size, and get an instant answer with a step-by-step breakdown. Metric and imperial units supported.
How helium balloons create lift
Helium is about seven times lighter than air, so a balloon filled with helium displaces air that weighs more than the balloon itself. This creates a net upward force called buoyancy, described by Archimedes's principle: the buoyant force equals the weight of the fluid displaced. For a standard 11-inch latex balloon, the helium inside displaces about 26 litres of air (roughly 31 grams) while the helium itself weighs about 4 grams and the balloon skin adds another 2-3 grams, leaving a net lift of around 12 grams. The bigger the balloon, the more air it displaces and the more it can lift.
How to use this calculator
Switch between two modes using the dropdown at the top. In "Lift" mode, enter the weight of the object you want to lift along with the balloon size and your altitude (important if you are at elevation, because thinner air reduces lift). The calculator returns the minimum number of balloons with a built-in 5% safety margin. In "Tank" mode, pick your helium tank size and fill level to see how many balloons you can inflate from one cylinder. In either mode, entering your tank rental cost gives you a per-balloon helium price.
Altitude and temperature effects
At higher altitudes the air is thinner, which means there is less air displaced by each balloon and therefore less lift. At 2,000 metres (about 6,500 feet) a balloon lifts roughly 21% less than at sea level. Temperature also matters: cold air is denser, which actually increases lift slightly, while hot air is less dense and reduces it. This calculator uses a standard barometric approximation for altitude. For critical lifting applications - scientific payloads or weather balloons - use precise atmospheric data for your launch site.
Balloon types and float time
Standard latex balloons are porous: helium escapes slowly through the material, so they typically float for 8-24 hours untreated, or up to several days when coated with a gel sealant (Hi-Float). Foil (mylar) balloons are far less porous and can float for days to weeks. Mixing air into the fill (using 80% or 60% helium) stretches your tank further but reduces float time because the diluted gas provides less buoyancy per unit volume. For outdoor events on a warm day, always inflate on-site and leave a little head-room between the balloon and its full diameter to allow for gas expansion.
Helium balloon size reference
| Diameter | Common name | Helium volume | Net lift | Typical use |
|---|---|---|---|---|
| 5 inch | Mini | 2.5 L | 3 g | Party favors, garlands |
| 9 inch | Small | 14 L | 8 g | Small displays, bouquets |
| 11 inch | Standard | 26 L | 12 g | Most common party balloon |
| 16 inch | Big | 80 L | 38 g | Centrepieces, arches |
| 18 inch | Large | 114 L | 56 g | Foil-size equivalent |
| 24 inch | Huge | 270 L | 133 g | Statement displays |
| 30 inch | Giant | 524 L | 261 g | Photo ops, outdoor events |
| 36 inch | Jumbo | 906 L | 450 g | Large installations |
Net lift capacity and helium volume for standard latex balloons at sea level. Lift decreases with altitude.
Frequently asked questions
How many 11-inch balloons does it take to lift 1 kg?
At sea level, each standard 11-inch latex balloon provides about 12 grams of net lift. To lift 1 kilogram (1,000 grams) with a 5% safety margin you need ceil(1,050 / 12) = 88 balloons. At higher altitudes you need more, because thinner air reduces the buoyant force.
How many helium balloons would lift a person?
An average adult weighs about 70 kg (154 lb). Using standard 11-inch balloons at sea level: 70,000 g x 1.05 margin / 12 g per balloon = roughly 6,125 balloons. Larger balloons reduce the count: 36-inch jumbo balloons each lift about 450 grams, so you would only need around 163 of them.
How many balloons does a standard helium tank fill?
A common medium party tank holds about 422 litres of helium. Each 11-inch balloon takes about 26 litres, so one tank fills roughly 16 balloons. A larger 55 cu ft cylinder (about 1,557 litres) fills around 60 balloons of the same size.
Does balloon size affect how long they float?
Yes. Larger balloons have a higher volume-to-surface-area ratio, so helium escapes more slowly relative to the total volume. A 16-inch balloon may float a day or two longer than an 11-inch one under identical conditions. Applying a sealant like Hi-Float to the inside of latex balloons before filling can extend float time by several days.
Can I mix air with helium to save gas?
You can, but the balloon will not float unless there is enough helium. Below about 50-60% helium concentration the balloon becomes too heavy to achieve positive lift. The sweet spot for economy is 80% helium, which extends the tank by 25% but still gives a full day of floating for most events. The calculator's "fill level" selector models this tradeoff.
Why add a safety margin?
Lift values vary with actual fill pressure, temperature, balloon age, and how spherical the balloon is. A 5% margin ensures that the minimum balloon count given is enough to achieve real lift-off even under slightly unfavourable conditions. For a public event or a load-bearing application, add an extra 10-20% buffer on top.