🎈Balloon Lift Calculator - Hot-Air Balloon, Helium Lift, Burst Altitude

How to use Hot-Air & Helium Balloon Lift Calculator

1. 1On the Hot-air tab, pick an envelope size or type a volume, and set inside temperature, ground temperature, elevation, empty mass and payload
2. 2Read the lift per m³, net lift, float temperature and equilibrium altitude, then press Launch to watch the ascent
3. 3On the Helium tab, compare gases and set balloon size and body mass to see how many balloons you need
4. 4On the Weather balloon tab, pick a balloon, payload and free lift for burst altitude and ascent rate; use Weighing in air for the buoyancy correction

FAQ

How much can one cubic metre of hot air lift?

Hot-air lift comes from the density difference between outside and inside air. At the same pressure density is inversely proportional to absolute temperature: with 15 °C (288 K) outside and 100 °C (373 K) inside, the densities are about 1.225 and 0.946 kg/m³, a difference of 0.28 kg/m³. So each cubic metre lifts only about 280 g. A common 3000 m³ envelope gives about 840 kg of gross lift, and after roughly 400 kg of envelope, basket, burners and fuel it carries three or four people. Cold air widens the difference, which is why balloons usually fly at dawn.

Why do helium balloons float, and how much better is hydrogen?

The buoyant force equals the weight of the air displaced. At sea level and 15 °C, air is about 1.225 g/L and helium about 0.17 g/L, so each litre gives about 1.06 g of net lift. Hydrogen at 0.085 g/L gives about 1.14 g, only around 8% more, because both are so much lighter than air that the air’s weight dominates. Hydrogen is cheaper but flammable, which is why airships and party balloons use helium.

How many helium balloons would it take to lift a person?

A 28 cm party balloon holds about 11.5 L and gives about 12 g of buoyancy; after about 3 g of latex roughly 9 g is left. Lifting a 70 kg person therefore takes about 7,700 balloons, before counting string and a seat. The house in “Up” carries a little over twenty thousand balloons, but a small wooden house weighs tens of tonnes and would need millions of such balloons, a couple of orders of magnitude more than the film shows.

How high does a weather balloon go before it bursts?

The amount of helium inside is fixed, so as the outside pressure drops the volume grows as V = V₀(p₀/p)(T/T₀), and the balloon bursts when its diameter reaches the latex’s burst diameter. A 600 g balloon bursts at about 6 m across; with a 1 kg radiosonde it typically pops at 25–30 km after expanding dozens of times in volume. The net lift stays constant with height (equal to the free lift at launch), the ascent rate is about 5–7 m/s and the climb takes around an hour. Bigger balloons and lighter payloads go higher.

Why do precise weighings need an air-buoyancy correction?

A balance compares weight minus buoyancy of the object against that of the reference weights. The weights are usually steel at about 8000 kg/m³; a less dense object displaces more air and reads low. The correction is m_true = m_read × (1 − ρ_air/ρ_weights)/(1 − ρ_air/ρ_object). A kilogram of water reads about 1 g light (0.1%), while a kilogram of styrofoam really has about 4% more mass, which is the physics answer to “which is heavier, a kilo of feathers or a kilo of iron?”