Milliamp Hour (mAh) to Watt Hour (Wh) Calculator

Convert battery capacity from Milliamp Hours (mAh) to Watt Hours (Wh). Enter your battery's capacity and voltage to calculate the energy storage in Watt Hours.

Battery Specifications

How to Use this Milliamp Hour (mAh) to Watt Hour (Wh) Calculator?

To convert battery capacity from milliamp hours (mAh) to watt hours (Wh), you'll need:

  • Battery Capacity (mAh): The milliamp-hour rating found on your battery or device specifications
  • Battery Voltage (V): The nominal voltage of your battery
  • Conversion Efficiency: Accounts for energy conversion losses:
    • 100%: Ideal theoretical conversion (not realistic)
    • 95%: High efficiency in optimal conditions
    • 90%: Typical real-world conditions
    • 85%: Conservative estimate for planning

Understanding Battery Energy Capacity

Converting between mAh and Wh involves several important concepts:

  • Basic Formula: Wh = (mAh × V) ÷ 1000
  • Common Battery Voltages:
    • 3.7V: Common Li-ion cells
    • 7.4V: 2-cell Li-ion packs
    • 11.1V: 3-cell Li-ion packs
    • 14.8V: 4-cell Li-ion packs
  • Energy Density: Higher voltage batteries store more energy for the same mAh rating

Factors Affecting Energy Capacity

Several factors can impact the actual energy available from your battery:

  • Temperature Effects:
    • Optimal range: 20-35°C (68-95°F)
    • Cold reduces available capacity
    • Heat increases self-discharge
    • Extreme temperatures can damage cells
  • Load Characteristics:
    • Higher loads reduce efficiency
    • Pulsed loads may affect capacity
    • Constant vs. variable power draw
  • Battery Age and Health:
    • New batteries provide rated capacity
    • Typical annual capacity loss: 10-20%
    • Charge cycles affect capacity

Common Applications and Power Requirements

Different devices require different energy capacities:

  • Mobile Devices:
    • Smartphones: 10-15Wh
    • Tablets: 20-40Wh
    • Laptops: 40-100Wh
  • Portable Electronics:
    • Wireless earbuds: 0.5-1Wh
    • Action cameras: 5-8Wh
    • Portable speakers: 10-30Wh
  • Power Tools:
    • Cordless drills: 30-60Wh
    • Leaf blowers: 100-200Wh
    • Lawn mowers: 200-500Wh

Frequently Asked Questions (FAQ)

Basic Concepts

What's the difference between mAh and Wh?

These units measure different aspects of battery capacity:

  • mAh (milliamp hours): Measures electric charge capacity
  • Wh (watt hours): Measures energy storage capacity
  • Wh takes voltage into account, making it better for comparing different battery types
  • mAh is only meaningful when comparing batteries of the same voltage
Why do we need both measurements?

Different measurements serve different purposes:

  • mAh is useful for comparing cells of the same chemistry
  • Wh is better for calculating runtime and energy requirements
  • Some regulations (like air travel) use Wh ratings
  • Device manufacturers may use either or both
How accurate is the conversion?

Conversion accuracy depends on several factors:

  • Voltage stability throughout discharge
  • Operating temperature
  • Load characteristics
  • Battery age and condition
  • Measurement precision

Technical Questions

How do I calculate runtime?

To estimate runtime:

  • Formula: Runtime (hours) = Wh ÷ Power Draw (W)
  • Account for efficiency losses
  • Consider variable power draw
  • Add 20% safety margin
What affects battery efficiency?

Efficiency is influenced by:

  • Internal resistance
  • Temperature conditions
  • Discharge rate
  • Battery chemistry
  • Age and usage history
How do parallel and series connections affect Wh?

Battery configurations change total energy:

  • Series: Voltage adds, mAh stays same
  • Parallel: mAh adds, voltage stays same
  • Total Wh adds in both configurations
  • Consider balancing requirements

Practical Applications

How do I choose the right battery size?

Consider these factors:

  • Device power requirements
  • Desired runtime
  • Weight and size constraints
  • Cost considerations
  • Safety requirements
What are the air travel restrictions?

General guidelines for lithium batteries:

  • Carry-on: Maximum 100Wh without approval
  • 100-160Wh: Airline approval required
  • Over 160Wh: Usually prohibited
  • Check airline specific policies
How can I maximize battery life?

Best practices include:

  • Avoid extreme temperatures
  • Maintain partial charge for storage
  • Avoid deep discharges
  • Use appropriate chargers
  • Monitor battery health