Interactive tool
CPAP Battery Runtime Calculator
Pick your machine, humidifier setting, connection, and battery to estimate how long it will run — and the minimum capacity you need for a full night.
Batteries that cover this
How this is calculated
Runtime = battery capacity (Wh) ÷ power draw (W) × an efficiency factor (0.85–0.90 for a DC cable, 0.70–0.80 for an AC inverter), with a 15% safety buffer applied to the conservative end for battery age and cold weather. Machine draws are tested averages; see the full runtime methodology and tables.
These are estimates. Your machine's actual draw varies with pressure, mask leak, altitude, and battery age and temperature. Check the label on your power supply, and don't rely on this tool for medical decisions.
New to this? Start with the CPAP battery backup guide or see the best batteries roundup.