Lantern and torch run time
A guide, not advice. Check your kit maker's figures before you buy or pack.
The calculator needs JavaScript. The worked example, sum and figures below show exactly how it works, so you can do it yourself. A guide, not advice.
Short answer
Enter the voltage and capacity from the battery label, the lamp's power draw and your expected hours of use. The estimate calculates runtime from those figures and is not a guarantee; battery condition, temperature and lamp settings affect real use.
Worked example
| You enter | Value |
|---|---|
| Battery voltage from its label | 3.7 V |
| Battery capacity from its label | 2.5 Ah |
| Lamp power draw from its label | 2 W |
| Battery capacity you plan to use | 80% |
| Hours you plan to use the lamp each night | 4 h |
About 0.0 hours of runtime from the entered figures
| Result | Value |
|---|---|
| Estimated runtime | 0.0 hours |
| Estimated nights at your use | 0.0 nights |
Show the working
- Usable energy: 3.7 V × 2.5 Ah × 0.8% = 0.1 Wh
- Runtime: 0.1 Wh ÷ 2 W = 0.0 h
- Nights: 0.0 h ÷ 4 h/night = 0.0
How it works
- Battery energy = voltage × amp-hours × usable share
- Runtime = usable battery energy ÷ lamp power draw
- Nights = runtime ÷ hours of use each night
Use compatible battery and lamp figures from their labels. Capacity varies with battery type, age, temperature and load; this estimate is not a guarantee.
Our figures (adjustable)
These are our planning allowances and, once checked, typical figures with their sources. They aren't facts about your kit: change any of them in the calculator.
This calculator has no built-in defaults: every figure comes from you or your kit's own label.
What to buy
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FAQs
How long will my lantern last?
It depends on the battery and brightness setting. Use the maker's runtime figures if available; this tool estimates from the label values you enter.
Can I use a power bank's mAh rating directly?
Check its voltage and energy rating, and follow its maker's instructions. mAh alone does not show the energy available at every output voltage.
Guides that use it
Best camping lanterns
Best camping lanterns: calm, practical help for UK families and first-timers, from the Canvasdale team.