Battery Life Calculator

Category: Technology
- April 08, 2025
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Calculate how long your battery will last based on capacity and current draw.

V
%
? Account for energy loss in the system. Typical values range from 80-95%.

Advanced Options

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About Battery Life Calculations

This calculator estimates how long a battery will power a device based on the battery's capacity and the device's power consumption.

Battery Capacity

Battery capacity is typically measured in milliamp-hours (mAh) or amp-hours (Ah), indicating how much current a battery can supply over time. Some batteries are rated in watt-hours (Wh), which accounts for both current and voltage.

Current Draw

Current draw is the amount of electrical current a device requires to operate, measured in milliamps (mA) or amps (A). Power consumption can also be measured in watts (W), which is voltage multiplied by current.

Battery Life Formula

The basic formula for calculating battery life is:

Battery Life (hours) = (Battery Capacity (mAh) × Efficiency) ÷ Current Draw (mA) × (Depth of Discharge ÷ 100)

When using watt-hours and watts, the formula becomes:

Battery Life (hours) = (Battery Capacity (Wh) × Efficiency) ÷ Power Consumption (W) × (Depth of Discharge ÷ 100)

This calculator provides estimates only. Actual battery life may vary based on temperature, battery age, and load conditions.

What Is the Battery Life Calculator?

The Battery Life Calculator is a practical tool for estimating how long your battery will power a device based on its capacity, voltage, and energy usage. Whether you're working on an Apple desktop using an iMac computing tool or testing portable electronics, this calculator helps you plan your power usage effectively.

It’s especially useful for electronics enthusiasts, engineers, students, or anyone using battery-powered equipment. The calculator can help prevent unexpected shutdowns, estimate charging intervals, and choose the right battery for your needs.

Battery Life Calculation Formula

Using Current Draw:
Battery Life (hours) = (Battery Capacity (mAh) × Efficiency ÷ 100 × Depth of Discharge ÷ 100) ÷ Current Draw (mA)

Using Power Consumption:
Battery Life (hours) = (Battery Capacity (Wh) × Efficiency ÷ 100 × Depth of Discharge ÷ 100) ÷ Power Consumption (W)

How to Use the Calculator

Follow these simple steps to estimate your battery life:

  • Enter Battery Capacity – Choose the unit (mAh, Ah, or Wh).
  • Input Battery Voltage – Voltage is needed for accurate conversions.
  • Set Current Draw – Select the unit (mA, A, or W) that matches your device's usage.
  • Adjust Efficiency – Default is 85%, but you can change this based on your system.
  • Enable Advanced Options (Optional) – Choose a battery type and depth of discharge if needed.
  • Click "Calculate" – View estimated runtime, power consumption, and a breakdown of the calculation steps.

Why This Calculator Is Useful

This tool is more than just a number cruncher. It provides actionable insights for:

  • Planning power usage in DIY electronics or mobile setups
  • Evaluating battery health or performance over time
  • Comparing batteries for drones, sensors, or laptops
  • Choosing appropriate batteries for gaming setups and system power analysis

Whether you're running tests on an Apple desktop math project or integrating sensors into a network that also requires transfer speed estimation, this calculator simplifies decision-making.

Frequently Asked Questions

What does “Depth of Discharge” mean?

It’s how much of your battery's total capacity you plan to use. For example, 80% means you won’t fully drain the battery, helping preserve its lifespan.

How accurate are the results?

The calculator gives solid estimates based on your inputs. Real-world battery life may vary due to temperature, battery age, or changes in device usage.

Can this calculator be used for rechargeable batteries?

Yes. You can select from various types like Lithium-ion, NiMH, and Lead Acid in the advanced settings.

Do I need to know the voltage?

Yes, voltage is essential for converting between amp-hours and watt-hours, especially when comparing power usage and capacity.

Can this tool help with PC or gaming setups?

Absolutely. Combine it with a Power Supply Calculator or Bottleneck Calculator to analyze total power needs and component efficiency.

Bonus Utility for Enthusiasts

This Battery Life Calculator pairs well with tools like the Download Speed Calculator to evaluate internet speed in portable devices, or the Transfer Speed Calculator to plan data usage while off-grid. It's a great companion to an iMac number cruncher or any macOS arithmetic tool for users who want quick, reliable answers.

Final Tip

For the most accurate result, ensure your device’s actual power draw is measured under normal operating conditions. Estimating too low can cause power failures, and estimating too high may lead to overpaying for oversized batteries.