Battery Runtime Calculator

Estimate runtime from battery capacity in mAh and device current draw.

Category: Life Tools

When to use?

Use it to estimate how long a power bank, IoT device, case, or portable gadget can run before recharging.

How to use

  • Enter battery capacity in mAh.
  • Enter device current draw in mA.
  • Check the estimated runtime.

Input Explanation

Enter total battery capacity and the device's average current draw.

Calculation Basis

Runtime = capacity ÷ current draw × efficiency, using about 85% efficiency for a practical estimate.

Usage Examples

  • Power bank planning - Estimate phone or device charging time from capacity.
  • IoT battery life - Estimate how often a low-power device needs battery replacement.
  • Compare devices - Change current draw to compare runtime by device mode.

Examples

  • 10,000 mAh battery, 500 mA draw → about 17 hours
  • 5,000 mAh case, 50 mA draw → about 85 hours

Cautions

  • This is an estimate for everyday planning. Actual results can vary by environment, product specifications, personal condition, and local rules.

Guides

Runtime formula

Theoretical runtime is battery capacity in mAh divided by device current in mA. Applying efficiency gives a more realistic estimate.

Real-world loss

Temperature, battery age, conversion loss, screen brightness, and wireless usage can shorten runtime.

FAQ

Why is actual runtime shorter?

Conversion loss, battery age, temperature, and usage pattern reduce actual runtime.

How do I find current draw?

Divide power consumption in watts by voltage to estimate current.

Does it work for power banks?

Yes, but conversion loss means the real result is usually lower.

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