What this calculator does
Helium lifts about 1.07 grams per litre, the difference between the density of air and the density of helium. An 11 inch balloon holds 11.42 litres and therefore lifts 12.24 g, so lifting 500 g takes 41 of them.
Balloon size is what dominates the count, because volume grows with the cube of the diameter. Going from 11 inch to 24 inch balloons takes the count from 41 to 4, a factor of ten for barely more than double the diameter. The figure here is the gross lift, and the weight of the balloon itself and any string is not deducted.
The formula
Lift per litre is the density of air minus the density of the gas, about 1.0715 g/L for helium and 1.0785 for hydrogen. The balloon volume is four thirds π r³, using the diameter converted from inches. Dividing the payload by the lift per balloon and rounding up gives the count, which is why the total lift available usually exceeds the payload slightly.
| Term | Meaning |
|---|---|
| Lift per litre | Air density minus gas density, about 1.07 g/L for helium at sea level. |
| Gross lift | What the gas can lift before subtracting the balloon, string and any attachment. |
| Net lift | What is actually available after those weights, which is what matters in practice. |
| Float time | How long a balloon stays up, limited by helium escaping through the latex rather than by lift. |
The inputs explained
| Field | What to enter |
|---|---|
| Weight to lift (g) | The weight to lift, in grams. Remember that the balloons and string are not deducted, so add their weight to the payload for a realistic figure. |
| Balloon diameter (in) | Balloon diameter in inches. 11 inch is the standard party balloon. |
| Gas | Helium or hydrogen. Hydrogen lifts marginally more but is flammable and is not used for decoration. |
When to use it
Lifting a decoration or a sign
The count needed rises quickly with weight, and a surprisingly heavy payload can be lifted by a large enough cluster.
Comparing balloon sizes
Larger balloons are dramatically more efficient per balloon, though they use the same helium per unit of lift.
Estimating helium needed
The total gas volume figure translates into cylinder size, which is usually the real constraint.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many balloons does 500 g need?
The same payload lifted by balloons of different sizes.
| Balloon diameter | Balloons needed | Lift per balloon | Total gas volume |
|---|---|---|---|
| 9 in | 75 | 6.70 g | 469.1 L |
| 11 in | 41 | 12.24 g | 468.2 L |
| 16 in | 14 | 37.66 g | 492.0 L |
| 18 in | 10 | 53.62 g | 500.4 L |
| 24 in | 4 | 127.09 g | 474.5 L |
Questions
How much can a helium balloon lift?
A standard 11 inch balloon lifts about 12.2 g of gross lift. Subtract the balloon itself, which is roughly 3 g of latex for that size, plus any string, and the usable net lift is closer to 8 or 9 g. A single balloon will not lift much more than a light card.
Does this include the weight of the balloon?
No, it calculates gross lift from the gas alone. Latex weighs a few grams for a party balloon and more for larger sizes, and string and a ribbon add more. Add those to your payload figure for a realistic count.
Do bigger balloons use less helium?
No. The lift comes from the volume of gas, so lifting a given weight needs roughly the same total helium regardless of how it is divided up. Bigger balloons mean fewer balloons and less latex, but the cylinder empties at the same rate.
Why do helium balloons sink after a day?
Helium atoms are small enough to diffuse through latex, so the balloon slowly loses gas and therefore lift. A latex balloon typically floats 12 to 24 hours. Foil balloons hold helium far longer, often a week or more, because the film is much less permeable.
For a balloon arch instead, see the balloon arch calculator. For planning the room, see the event seating calculator.