This calculator estimates how long a battery will power your portable ham radio station based on its capacity and the radio's current draw in both receive and transmit modes.

If you enter both RX and TX current values along with a transmit duty cycle (e.g. 20% TX, 80% RX), the calculator will compute an average current draw based on usage pattern.

Basic formulas:

• Watt-hours = Ah × Voltage
• Average Current = TX × % + RX × (1 - %)
• Runtime (hours) = Wh ÷ (Average Current × Voltage)

Example: A 12Ah LiFePO₄ battery running a 5W QRP radio at 13.8V with 0.5A RX and 2A TX at 20% duty cycle might last 15–20 hours.