How to Know Your Battery Size

You can usually find your battery size by checking the label printed on the battery itself, looking in your device’s or vehicle’s manual, or using the manufacturer’s website or an identification code (like group size or model number) printed on the battery. Below is a detailed guide for phones, laptops, electric vehicles, and conventional cars.

What “Battery Size” Really Means

When people ask about battery size, they may mean different things: the physical dimensions, the capacity (how much energy it stores), or the specification standard (like a group size code or model code). Understanding which of these you need helps you know where to look and what number to pay attention to.

Key Ways Battery Size Is Described

Battery size can be expressed in several technical ways depending on the device or vehicle. Knowing the terminology makes it easier to read labels and manuals correctly.

The list below explains the main types of “battery size” measurements you’ll encounter.

• Capacity (energy): Usually shown as watt-hours (Wh) or milliamp-hours (mAh). This tells you how much energy the battery can store and is common for phones, laptops, and e-bikes.
• Voltage (V): The nominal operating voltage of the battery or pack. Examples: 3.7 V for many phone cells, 12 V for most car starter batteries, 400–800 V for many EV packs.
• Physical dimensions: The actual size of the battery, often listed in millimeters for small devices or as length/width/height for car batteries.
• Standardized size codes: Such as 18650 or 21700 cells in electronics, BCI group sizes (e.g., Group 48, Group 35) in car batteries, or manufacturer pack codes in EVs.
• Pack energy in EVs: Measured in kilowatt-hours (kWh) such as 55 kWh, 77 kWh, or 100+ kWh, which is the most common way to describe EV battery size.

Together, these measurements define not just how big a battery is physically, but how much power and runtime you can expect and what will be compatible when you replace or upgrade it.

Finding Battery Size in Phones and Tablets

For smartphones and tablets, battery size is almost always given in milliamp-hours (mAh) and sometimes watt-hours (Wh). Because the batteries are usually sealed, you’ll rely on documentation and software rather than opening the device.

Check the Device Settings and Documentation

Many manufacturers publish battery size details directly in system settings or official documentation. This is often the quickest, most reliable method for modern phones and tablets.

The following list outlines where to look for this information on common platforms and from typical sources.

• Manufacturer tech specs page: Search for your exact model name (for example, “iPhone 15 Pro battery capacity”) on the manufacturer’s website. Specs often list capacity in mAh or Wh.
• Product box or quick-start guide: New devices sometimes list battery capacity on the packaging or in the included leaflet.
• Settings on Android: Capacity isn’t always shown directly in Settings, but some brands include it under About phone → Battery or Status. If not, you’ll need the official spec sheet or a reputable device database.
• Settings on iOS (iPhone, iPad): Apple does not show battery capacity in mAh in the system menus. You must check Apple’s technical specifications online or trusted teardown/spec sites.
• Regulatory labels: Some tablets and older phones have fine-print regulatory text on the back or under a removable cover that includes Wh or mAh.

Using these sources ensures that the battery size you find matches your exact model and configuration, which is critical when comparing performance or planning replacements.

Use Third-Party Tools With Caution

There are apps and databases that claim to reveal your battery capacity, but they can be imprecise or outdated if they rely on crowdsourced data.

The points below highlight how to approach third-party tools safely.

• Device-info apps (Android): Apps such as AIDA64 or Device Info HW may show battery design capacity pulled from system data, but this can be missing or approximate.
• Online device databases: Sites like GSMArena or NotebookCheck often list battery size for phones and tablets, but always verify you’re looking at the correct model variant.
• Avoid rooting or risky tools: You don’t need advanced or invasive tools just to confirm battery size; stick to read-only utilities and official documents.

Third‑party tools can be helpful cross-checks, but they should support, not replace, the official specifications you get from the manufacturer.

Determining Laptop Battery Size

Laptop batteries are commonly described in watt‑hours (Wh), sometimes alongside milliamp‑hours (mAh). Since many modern laptops have internal batteries, you’ll usually read the size through software or manufacturer specs rather than by opening the computer.

Check System Information and Power Settings

Most laptops expose battery design capacity through built‑in system tools. This is often the simplest way to see the original battery size even if the battery has degraded.

The list below shows common methods on major operating systems.

• Windows (battery report):
  

  • Open Command Prompt or PowerShell as a normal user.
  • Run: powercfg /batteryreport.
  • Open the generated battery-report.html file (typically saved to your user folder).
  • Look for Design Capacity (in mWh); divide by 1,000 to get Wh (e.g., 60,000 mWh ≈ 60 Wh).

• macOS:
  

  • Click the Apple menu → About This Mac → System Report.
  • In the sidebar, choose Power.
  • Look for Full Charge Capacity and Cycle Count; original design capacity may appear in documentation.

• Linux:
  

  • Check /sys/class/power_supply/ for your battery (often BAT0).
  • Read values such as energy_full_design or charge_full_design and convert µWh or µAh to Wh.

These tools typically reveal both the design capacity and the current full charge capacity, letting you see the original size and how it has changed over time.

Inspect the Battery Label or Manufacturer Specs

If you can access the battery or prefer official documentation, labels and spec sheets will give you the most direct statement of battery size.

The following methods explain where to find this information without guesswork.

• Check the manufacturer’s product page: Search for your laptop model plus “specifications” or “battery capacity.” Battery size is usually listed in Wh (e.g., “56 Wh” or “4‑cell 52 Wh”).
• Printed label on removable batteries: On older or business laptops with removable packs, the label often shows something like “10.8 V, 5200 mAh, 56 Wh.”
• Service manuals: Official maintenance or service manuals, often downloadable from the manufacturer’s site, list battery part numbers and capacities.

Combining software reports with label or spec-sheet data gives you a clear understanding of both original battery size and its current condition.

Finding Battery Size in Electric Vehicles (EVs)

In electric cars and many plug‑in hybrids, battery size is almost always quoted in kilowatt‑hours (kWh). This figure is central to range estimates and charging times and is typically included in marketing material and technical data.

Identify the EV Battery Size in kWh

EV manufacturers prominently publish pack sizes because they strongly influence driving range and price. You can usually confirm your battery size without any physical inspection of the pack.

The list below details the most reliable ways to find an EV’s battery size.

• Owner’s manual: Look in the technical specifications or “high‑voltage battery” section for a value like “Battery energy: 77 kWh (gross), 70 kWh (usable).”
• Window sticker / Monroney label (U.S.): New EVs often list battery capacity and EPA range on the sales sticker.
• Manufacturer website or configurator: EV trim names often include the pack size (e.g., “Standard Range 55 kWh” or “Long Range 82 kWh”). Check your exact trim and model year.
• Vehicle information screen: Some EVs show high‑voltage battery data in the infotainment system or service menus, occasionally including approximate usable capacity.
• VIN decoders and EV databases: Some specialized sites link VINs or trim codes to known pack sizes; confirm that the source is current and model‑year specific.

Because EV trim levels and pack sizes can change by market and year, it is essential to match your exact model and build when reading these figures.

Gross vs. Usable Battery Capacity

EVs often advertise one battery size but make only a portion of it available for driving to preserve battery health. Understanding this difference avoids confusion when comparing real‑world range and charging behavior.

The points below outline how to interpret the numbers you may see.

• Gross capacity: The total physical capacity of the pack (e.g., 82 kWh). This is sometimes quoted in technical specs but may not equal what you can use.
• Usable capacity: The portion accessible to the driver (e.g., 76 kWh usable out of 82 kWh gross). This more closely reflects your practical driving range.
• Buffer at top and bottom: Manufacturers reserve upper and lower state‑of‑charge margins to slow degradation and protect the pack.
• Marketing differences: Some brands emphasize gross capacity, others usable; detailed spec sheets or independent testing can clarify which figure is being cited.

By paying attention to whether the number is gross or usable, you can better compare different EVs and interpret range claims more realistically.

Determining Car Battery Size (Conventional 12 V Batteries)

For gasoline and diesel cars, “battery size” usually refers to the physical size standard (often called group size), along with cold cranking amps (CCA) and sometimes amp‑hour (Ah) rating. These details are essential when replacing a starter battery.

Understand Group Size, CCA, and Ah

Automotive starter batteries follow standardized codes that define dimensions, terminal types, and performance. Knowing these helps you choose a compatible replacement.

The list below summarizes the primary specifications you’ll encounter on a typical 12 V car battery.

• BCI Group size (North America): A code such as Group 24, 35, 48, or 94R that defines physical dimensions and terminal locations. This is often printed clearly on the battery label.
• EN/ DIN codes (Europe and others): European and other regions may use different coding systems to describe size and cranking capability.
• Cold Cranking Amps (CCA): Indicates how much current the battery can deliver at low temperatures; higher CCA is usually better for cold climates.
• Amp‑hour rating (Ah): Commonly seen on AGM or deep‑cycle batteries; represents stored charge, relevant for camper vans, boats, and accessories.
• Reserve capacity (RC): Number of minutes the battery can deliver a specified load; important for vehicles with high electrical demand.

These parameters together define not just the battery’s physical size but also whether it can reliably start your engine and power your vehicle’s systems.

Locate Your Car Battery Size

Once you understand the codes, you can find your car battery size by inspecting the battery, consulting the manual, or checking fitment guides from retailers.

The steps below show where to look and what information to note.

• Check the existing battery label: Pop the hood, locate the battery, and look for a printed group size (e.g., “Group 48”), CCA rating, and sometimes Ah. Write these down before shopping for a replacement.
• Owner’s manual: Most manuals include a section that lists the recommended battery type, group size, and minimum CCA for your engine.
• Parts retailers and fitment tools: Auto parts stores and major online retailers have lookup tools where you enter your make, model, year, and engine; they then show compatible battery sizes and specs.
• OEM part number: If you want exactly what the vehicle came with, ask a dealer for the original equipment part number and specification list.

By combining your current battery’s label details with the manufacturer’s recommendations, you can select a replacement that matches both physical fit and performance needs.

Identifying Battery Size in Smaller Electronics and Devices

For devices like cameras, power tools, e‑bikes, wearables, and smart home gadgets, battery size is often indicated directly on the pack or in user documentation, usually in mAh or Wh.

Check the Battery Pack and Product Label

Many removable and modular batteries show size information right on their casing. This is especially common for cameras, drones, and tools where batteries are meant to be swapped.

The following examples describe typical locations and formats for battery size information in consumer devices.

• Action cameras and DSLRs: The removable battery usually has an inscription such as “7.2 V, 1250 mAh, 9 Wh.” Filmmakers often track Wh to plan shooting days.
• Power tools (cordless drills, saws, etc.): Packs often state something like “18 V, 5.0 Ah (90 Wh).” Higher Ah generally means longer runtime on the same voltage platform.
• E‑bikes and scooters: The frame or battery housing typically lists voltage and Wh, for example “36 V, 14 Ah (504 Wh)” or “48 V, 750 Wh.”
• Wearables (smartwatches, trackers): Capacity is usually only in documents or spec sheets, as batteries are sealed and very small.
• Smart home devices: Removable cells might be standard sizes (AA, AAA, CR2032) where “size” is the cell type rather than a Wh rating.

Reading these labels provides concrete values that you can use to estimate runtime, compare models, or buy compatible spare batteries.

Converting Between mAh, Wh, and kWh

Because different products use different units, you may need to convert between mAh, Wh, and kWh to compare battery sizes fairly. This is straightforward if you know the nominal voltage.

Basic Conversion Formulas

Conversions rely on simple relationships between voltage, current, and energy. With just one or two numbers, you can translate between the units most commonly used in consumer electronics and vehicles.

The formulas below show how to convert between the most relevant units.

• Wh from mAh:
  

  • Formula: Wh = (mAh × V) ÷ 1000
  • Example: A 5,000 mAh phone battery at 3.85 V ≈ (5000 × 3.85) ÷ 1000 ≈ 19.25 Wh.

• mAh from Wh:
  

  • Formula: mAh = (Wh × 1000) ÷ V
  • Example: A 60 Wh laptop battery at 11.4 V ≈ (60 × 1000) ÷ 11.4 ≈ 5263 mAh.

• kWh from Wh:
  

  • Formula: kWh = Wh ÷ 1000
  • Example: An EV pack of 77,000 Wh is 77 kWh.

• Wh from kWh:
  

  • Formula: Wh = kWh × 1000
  • Example: A 0.5 kWh power station is 500 Wh.

Using these conversions, you can directly compare, for instance, a power bank’s Wh rating to a laptop battery or verify whether a manufacturer’s stated capacity is consistent with its voltage and mAh numbers.

What to Do If You Still Can’t Find Your Battery Size

Occasionally, especially with older or obscure devices, battery information can be hard to locate. In these cases, contacting the manufacturer or using trusted professional help is safer than guessing.

Practical Next Steps

If labels are worn off or manuals are missing, there are still options to identify a battery size accurately without risking damage or incompatibility.

The list below outlines reasonable steps when conventional methods fail.

• Contact customer support: Provide your exact model number and serial number; manufacturers often have internal documentation for legacy products.
• Visit an authorized service center: Technicians can open sealed devices safely and read internal labels or service documentation.
• Search service manuals and teardown guides: Enthusiast communities and repair sites sometimes document exact battery capacities and part numbers.
• Use part numbers printed on the pack: If you can see a partial code, searching that code online can lead you to matching replacement packs with listed capacities.

These approaches help you find reliable data without resorting to guesswork, which can lead to improper replacements or safety issues.

Summary

To know your battery size, start by identifying what kind of battery you’re dealing with—phone, laptop, EV, car, or other device—then check the most direct sources: the battery label, the device or vehicle manual, and the manufacturer’s official specifications. For phones and laptops, capacity is usually in mAh or Wh; for EVs, it’s in kWh; for conventional cars, it’s in standardized group sizes plus CCA and possibly Ah. When necessary, you can convert between mAh, Wh, and kWh using simple formulas, and if information isn’t obvious, manufacturer support, service centers, and repair documentation can fill in the gaps. Knowing your battery size not only helps with replacements but also with understanding runtime, range, and overall performance.

How do I tell what size battery I have?

Check the Owner’s Manual: The battery section of your car’s manual will list the recommended BCI Group Size and minimum CCA. Look at the Existing Battery: The current battery’s Group Size is often labeled on the top label or front of the battery.

Where to check battery size?

You can typically find these sizing numbers printed somewhere on your car battery or in the vehicle manual. In addition, the batteries are grouped into sizes based on their length, width and height in millimetres.

What does a 20000mAh battery mean?

20,000 mAh (milliampere-hour) means that a device, most commonly a power bank, has a storage capacity of 20,000 milliampere-hours. This is a measure of electrical charge, with a higher mAh value indicating more energy storage and longer potential charging times. A 20,000 mAh power bank can fully charge multiple smartphones or power a phone, tablet, or other devices for an extended period, making it ideal for travel or heavy use. 

• Higher capacity: A 20,000 mAh rating means the power bank can supply a total of 20,000 mAh to devices before it needs to be recharged. 
• Multiple charges: This capacity is enough to charge a standard smartphone multiple times, depending on the phone’s battery size. 
• Ideal for travel and heavy use: It’s a good option for weekend trips, when you’re away from outlets, or for users who need to keep multiple devices charged throughout the day. 
• Powering multiple devices: A 20,000 mAh power bank can simultaneously charge a phone and a tablet, or even a small laptop, though the number of charges for each will be less than if charging only one device. 
• Efficiency: While the rated capacity is 20,000 mAh, the actual usable capacity is lower due to energy loss during charging and voltage conversion (typically around 60-70%). 

How do I know my phone battery size?

Information option in the settings. You can always just search for battery. Information on the homepage of the settings. And so that is how to check your devices battery capacity in milliamp.