Estimate how long a camping lantern, LED lantern, rechargeable lantern, headlamp, or battery light will run. This lantern runtime calculator uses battery capacity, voltage, power draw, brightness setting, battery type, temperature, age, and reserve level.
Battery capacity:
Enter battery capacity in mAh, Ah, or Wh. If using mAh or Ah, enter battery voltage so the calculator can convert capacity to watt-hours.
Power draw:
Enter the lantern’s power draw in watts, amps, or milliamps. The calculator adjusts this based on brightness setting.
Real-world conditions:
Efficiency, battery type, temperature, battery condition, and reserve percentage are used to estimate more realistic usable runtime.
A lantern runtime calculator helps estimate whether a light will last through a campsite evening, overnight trip, weekend campout, power outage, or backpacking route.
Actual runtime depends on the lantern model, LED efficiency, battery age, temperature, brightness mode, battery chemistry, and whether the listed capacity is accurate.
The basic lantern runtime formula is:
Runtime = usable battery watt-hours ÷ adjusted power draw
Convert battery capacity to watt-hours, estimate usable energy after efficiency and reserve, then divide by the lantern’s power draw in watts.
Use watt-hours equals milliamp-hours divided by 1,000, then multiplied by voltage. For example, 10,000 mAh at 3.7 volts is about 37 Wh before losses.
Advertised runtime may use a lower brightness setting or ideal lab conditions. Cold, old batteries, high brightness, and voltage conversion losses can reduce runtime.
Yes. Lower brightness usually uses less power and can greatly increase runtime, while high brightness drains batteries faster.