Your battery size is its energy capacity, usually given in mAh or Wh (and in larger packs, kWh). You can find this information on the battery label, in the device’s settings, or on the manufacturer’s specifications. Understanding the size helps with replacements, estimating runtime, and comparing batteries.
Where to look for battery size in common devices
Different devices expose capacity in different ways. Here’s how to locate it for phones, laptops, and larger packs.
Smartphones and tablets
Most phones don’t show the exact mAh in the user interface. For many devices, you can still determine size by checking:
- Device settings (Android): Settings > Battery or Battery Health may show "Full Charge Capacity" or "Designed Capacity"; (iPhone): Settings > Battery > Battery Health shows the Maximum Capacity as a percentage of the original design capacity, not the raw mAh.
- Battery label or sticker (if accessible): Some devices have the battery's capacity listed on a label inside the device, often near the SIM tray or battery compartment.
- Packaging or official specs: The box or the manufacturer’s product page often lists the battery capacity in mAh or Wh.
- Teardowns or spec databases: Independent teardown sites (e.g., iFixit) and tech specs sites frequently publish the exact mAh for models.
Understanding this information helps you estimate how long the device will run between charges and what replacement to buy.
Laptops and larger devices
For laptops and tablets with removable or accessible batteries, you can usually find the size more easily:
- Battery label on the pack itself: Look for "Wh" (watt-hours) or "Ah" and "Voltage" to calculate Wh if needed.
- Operating system tools:
- Windows: Open a Command Prompt as administrator and run powercfg /batteryreport to generate a report showing Design Capacity and Full Charge Capacity (in mWh).
- macOS: About This Mac > System Report > Power shows Design Capacity and Current Capacity (often in mAh).
- Linux: Use upower or check /sys/class/power_supply/BAT*/ to view energy-full and energy-now.
- Manufacturer site or user manual: If the battery is sealed or not easily read, check the model number for the pack and look up its spec online.
These steps help you verify the exact energy capacity and assess battery health or match a replacement.
Electric vehicles and power tools
For larger packs, the capacity is typically specified in kilowatt-hours (kWh) or watt-hours (Wh):
- Electric vehicles: Check the vehicle’s spec sheet, window sticker, or the manufacturer website for the pack energy (e.g., 60–100+ kWh).
- Cordless tools and power packs: Look at the label on the battery pack (often 18V, 2.0Ah, which is 36Wh) or the product page for Wh or Ah at a given voltage.
- When in doubt: use the model number to search the official specs or trusted reviews for the exact pack rating.
Knowing the pack size helps you estimate driving range for EVs or runtime for tools and ensures you buy a compatible replacement.
Understanding the numbers: mAh, Wh, and voltage
Battery capacity can be expressed in milliampere-hours (mAh), watt-hours (Wh), or kilowatt-hours (kWh). The most universally comparable measure is Wh, because it accounts for voltage. To convert:
- Wh = (mAh × nominal voltage in V) / 1000
Small differences in nominal voltage across chemistries matter. For runtime estimates, use Wh as a baseline and consider real-world factors like temperature and age, which reduce usable capacity over time.
Practical steps you can take today
Use these steps to determine and verify your battery size quickly and accurately.
- Identify the device model number (often found in Settings > About phone, or on the device itself).
- Check the battery label or service manual for Wh, Ah, or mAh ratings.
- Look up official manufacturer specs for that model; cross-check with third-party teardowns or reviews for accuracy.
- If possible, review OS-based reports to confirm capacity (Windows battery report; macOS System Information).
- When replacing a battery, match not just capacity but form factor, voltage, and connector type.
The steps above help you avoid mismatches and ensure you buy the correct size and type for your device.
Summary
Knowing your battery size means identifying its energy capacity in mAh or Wh, and for large packs, kWh. Start with the label on the battery or the device’s official specifications, then use device-specific tools or OS reports to confirm values—especially as batteries age and health declines. When comparing batteries, Wh provides the most reliable basis for comparison because it reflects energy at the system voltage. Always verify compatibility before replacing a battery, and consider capacity loss over time due to age and temperature.