Helium Balloons Calculator (how many balloons to lift a weight)

Understanding the helium balloon lift calculator — concept and principle

This calculator works out how much one helium balloon can lift and how many balloons you need to lift a given weight, from the balloon size, the weight of the balloon and string, and the air temperature and pressure. It is useful for party decorations, science-class experiments and balloon photography projects.

Lift from the density gap: with the default inputs the result is 7 balloons (to lift 50 g).

How it is calculated

Gas densities from the ideal gas law: ρ = p × M ÷ (R × T), with M = 28.9647 g/mol for dry air, 4.002602 g/mol for helium, R = 8.314462618 J/(mol·K) and T in kelvin.
Balloon volume = π × d³ ÷ 6 (a sphere).
Gross lift = volume × (ρ_air − ρ_helium).
Net lift = gross lift − balloon and string weight.
Balloons needed = payload ÷ net lift, rounded up.

The principle

Archimedes' principle says a body in a fluid is pushed up by a force equal to the weight of the fluid it displaces. A helium balloon displaces air that is about seven times heavier than the helium inside, so the difference is available as lift. At room temperature and sea-level pressure, every litre of helium lifts a little over 1 gram. Because volume grows with the cube of the diameter, a slightly larger balloon lifts a lot more, while its own weight grows more slowly. Warm air and low pressure, as at high altitude, are less dense, so lift falls.

Worked example

Default inputs: 28 cm balloon, 4 g balloon and string, payload 50 g, 20 °C, 101.325 kPa.

Air density = 101,325 × 0.0289647 ÷ (8.3145 × 293.15) = 1.204 kg/m³; helium = 0.1664 kg/m³.
Volume = π × 0.28³ ÷ 6 = 0.01149 m³ = 11.5 L.
Gross lift = 0.01149 × (1.204 − 0.166) × 1,000 = 11.9 g; net lift = 11.9 − 4 = 7.9 g.
Balloons = 50 ÷ 7.93 = 6.3, rounded up to 7.
Helium for all = 7 × 0.0115 = 0.08 m³.

Each point is the calculator re-run with only “Weight to lift (g)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Weight to lift (g)	Balloons needed to lift the payload
12.5	2
25	4
37.5	5
50	7
62.5	8
75	10
100	13

How to read the result

Add a few extra balloons: real balloons are not perfect spheres, the gas is slightly compressed, and latex balloons lose helium through their walls within hours, so lift drops over the day. Foil balloons hold helium longer. Weigh the string and anything attached, because a few grams matter when each balloon lifts only about 8 g.

Common mistakes

Using the labelled balloon size when the balloon is under-inflated.
Forgetting the weight of the balloon and ribbon.
Expecting the same lift outdoors on a cold or hot day.
Assuming balloons will still float the next day.

Keep in mind: Do not release balloons outdoors: they become litter and can harm wildlife, and they must be kept away from power lines. Never inhale helium.

Frequently asked questions

How much can one helium balloon lift?

A 28 cm latex balloon lifts about 12 g gross, or about 8 g after its own weight.

How many balloons does it take to lift 50 g?

About 7 balloons of 28 cm.

How much does a litre of helium lift?

About 1 g at room temperature and sea-level pressure.

Sources: CODATA 2018 recommended values (molar gas constant R = 8.314462618 J/(mol·K)) · U.S. Standard Atmosphere, 1976 (dry air molar mass 28.9647 g/mol)

Checked 9 Nov 2026. Ideal gas law and Archimedes’ principle; standard values: molar gas constant R = 8.314462618 J/(mol·K) (CODATA 2018, exact), helium 4.002602 g/mol (IUPAC standard atomic weight), dry air 28.9647 g/mol (U.S. Standard Atmosphere 1976). Balloon size and weight are example values.

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