Device Battery Life Calculator
Estimate how long a battery lasts from its capacity and device power draw — phones, laptops, drones, or IoT sensors — plus recharge cycles and lifespan.
Continuous runtime (hours)
12.80
Breakdown
- Days per charge (at your usage)
- 2.55
- Energy stored (Wh)
- 17.30
- Usable energy (Wh)
- 14.70
- Average power draw (W)
- 1.16
- Charges per week
- 2.80
- Charges per year
- 143
- Battery lifespan (years)
- 3.50
Last updated:
FAQ
How do you convert mAh to hours?
Runtime is usable capacity divided by current draw: a 4,500 mAh cell at 85% health feeding a 300 mA load runs for about 12.75 hours. Voltage only matters for energy in watt-hours; the mAh figure already encodes the current budget.
Why account for battery aging?
Lithium cells lose capacity from day one — typically down to 80% after 300–500 full cycles. Budgeting 85% usable capacity gives estimates that stay honest after a year of ownership instead of matching only the spec sheet on day one.
How many years will the battery survive?
Divide the rated cycle count by your yearly charge cycles. Charging every 36 hours burns about 240 cycles a year, so a 500-cycle cell lasts roughly two years at that pace. Fewer deep cycles, less heat, and 20–80% charging windows stretch this considerably.
Related Calculators
Tip Calculator
→Calculate the tip amount and total bill per person, with smart service-quality presets and rounding options.
Split the Bill Calculator
→Split a bill fairly between friends, with optional tip and separate handling of shared vs personal items.
GPA Calculator
→Calculate your grade point average on a 4.0 scale from course grades and credit hours, with cumulative GPA support.
Grade Calculator
→Find what you need on the final exam to reach your target course grade, based on current grade and exam weight.