Hot Air Balloon Lift Calculator
Enter your balloon volume, ambient and envelope temperatures, and hardware masses to gauge how much payload you can safely carry and how much buoyant force remains for maneuvers or reserves.
How the lift calculation works
Warm air inside the envelope becomes less dense than the surrounding atmosphere. The buoyant force equals the weight of the displaced outside air minus the weight of the heated air inside: . Density follows the ideal gas relationship, so at constant pressure. The calculator uses a reference density of 1.225 kg/m³ at 15 °C (288.15 K) and scales by the temperatures you provide to approximate real flight conditions.
Subtracting the mass of the envelope hardware, propane, and payload yields the net lift available for reserves or climb maneuvers. A positive margin indicates remaining capacity, while a negative value means the balloon cannot lift the planned load without reducing mass or heating further. The reserve factor helps you hold back a portion of the theoretical lift for maneuvering safety.
Example flight profiles
| Operation | Volume (m³) | Inside temp (°C) | Payload (kg) | Remaining lift (kg) |
|---|---|---|---|---|
| Two-passenger sunrise flight | 2,200 | 90 | 210 | 85 |
| Tour balloon with full basket | 3,000 | 105 | 480 | 140 |
| High-altitude record attempt | 4,800 | 120 | 360 | 260 |
Plan your launch window
Combine this lift estimate with the Air Density Calculator for local weather adjustments, review takeoff performance using the Aircraft Takeoff Distance Calculator, and keep an eye on winds with the Crosswind Component Calculator when selecting launch sites.