Laptop Battery Runtime Calculator – Hours per Charge
Calculate laptop battery runtime from battery capacity and power draw.
About This Calculator
Calculate laptop battery runtime from battery capacity and power draw. Use the calculator above for instant results.
Worked Examples
- 56/15 × 90% = 3.36 hours | Light browsing/writing
Answer: ~3.4 hours
- 86/10 × 90% = 7.74 hours | Light tasks
Answer: ~7.7 hours
- 99/45 × 90% = 1.98 hours | Heavy gaming drains fast
Answer: ~2 hours gaming
Who Uses This Calculator?
Estimate battery life for travel.
Plan for working without power.
Choose laptop with sufficient battery.
Compare battery life across models.
Common Mistakes to Avoid
❌ Manufacturer ratings are best-case
Apple/Dell battery ratings are measured at minimum screen brightness doing light tasks. Real-world is typically 60-80% of rated runtime.
❌ Battery degrades with cycles
After 500 cycles, most batteries retain 80% capacity. After 1,000 cycles, often 60-70%. Battery runtime decreases with age.
Frequently Asked Questions
How to maximize battery life?
Lower screen brightness (biggest factor). Reduce CPU clock. Turn off WiFi/Bluetooth when not needed. Use power saving mode. Close background apps.
Wh vs mAh?
Wh = mAh × Voltage / 1000. 6,000 mAh at 11.1V = 66.6 Wh. Always convert to Wh for fair comparison across laptops.
M-series Mac battery life?
Apple Silicon (M1/M2/M3) MacBooks achieve 15-22 hours because ARM CPUs are extremely power efficient: 5-10W typical vs 15-25W for x86.