mAh to Wh Converter

Convert battery charge capacity into energy using MiniWebtool’s mAh to Wh Converter. Voltage connects mAh with Wh, while a travel-threshold comparison and estimated usable capacity at 5 V help you interpret a power bank’s rating.

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Help me understand MiniWebtool's mAh to Wh Converter: https://miniwebtool.com/mah-to-wh-converter/. What can I use it for, what inputs or settings do I need, and how do I use it and understand the output? Walk me through one simple example. Use this page as your source and answer in English.

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mAh to Wh ConverterTry it now — free ▼

Wh = mAh × V ÷ 1000: 20,000 mAh at 3.7 V is 74 Wh, under the 100 Wh airline limit.

Enter the capacity and voltage below to get watt-hours, the airline carry-on check against 100 Wh and 160 Wh, usable mAh at 5 V and run-time estimates; Wh to mAh works too.

Quick examples — click to fill the form, then press Convert:

Conversion Direction

Battery Type (fills voltage)

Capacity (mAh / Ah)

Switch the unit to Ah for large batteries (1 Ah = 1000 mAh).

Voltage (V)

Use the nominal voltage (~3.7 V for most power banks).

Embed mAh to Wh Converter Widget

About mAh to Wh Converter

The mAh to Wh Converter turns a battery's capacity in milliamp-hours (mAh) into watt-hours (Wh) using its voltage — and then does the one thing most converters skip: it tells you whether that battery or power bank is allowed on a plane. Enter a capacity and voltage (or pick a battery-type preset) and you instantly get the watt-hour figure, the FAA/IATA carry-on verdict on a visual gauge, the usable mAh you would actually get at a 5 V USB port, and relatable run-time estimates. It also works in reverse (Wh to mAh).

At a Glance

mAh to Wh Converter changes battery capacity between milliamp-hours and watt-hours using the battery voltage. It also checks the result against the 100 Wh and 160 Wh airline limits and estimates usable mAh at 5 V.

mAh to Wh Converter: features at a glance
Feature	What you get	Good for
Both directions	Wh = mAh × V / 1000, and mAh = Wh × 1000 / V. Enter capacity in mAh or Ah.	Comparing batteries rated in different units
Voltage presets	Nominal voltage presets for Li-ion cells, laptop, e-bike and other battery types.	Not knowing the nominal voltage of a battery
Airline check	Compares the result with the FAA/IATA thresholds: up to 100 Wh, 100 to 160 Wh with airline approval, and over 160 Wh.	Packing power banks and spare batteries for a flight
Usable mAh at 5 V	Estimates the mAh you can draw over USB at 5 V, assuming 85% conversion efficiency.	Understanding why a power bank delivers less than its label
Run-time estimates	Shows real-world run-time and charge equivalents for the energy in the battery.	Judging how long a battery might last
Formula steps	A step-by-step walkthrough and an animated capacity gauge show how the figures are derived.	Verifying the calculation

mAh to Wh Formula

Watt-hours are just charge multiplied by voltage. Because mAh are milli-amp-hours, you divide by 1000 to get the answer in watt-hours:

mAh to Wh

$$\text{Wh} = \frac{\text{mAh} \times \text{Voltage (V)}}{1000}$$

Wh to mAh (reverse)

$$\text{mAh} = \frac{\text{Wh} \times 1000}{\text{Voltage (V)}}$$

Example: a 20,000 mAh power bank built from 3.7 V lithium cells stores $ \frac{20000 \times 3.7}{1000} = 74 $ Wh of energy.

Why Convert mAh to Wh at All?

mAh measures electric charge, and charge alone does not tell you how much energy a battery holds — a 10,000 mAh battery at 3.7 V holds half the energy of a 10,000 mAh battery at 7.4 V. Watt-hours fold voltage into the number, so they measure true energy and let you compare any two batteries fairly. That is exactly why airlines, shipping couriers, and manufacturers all quote limits in Wh rather than mAh.

Airline Rules for Batteries and Power Banks

Air-travel rules for spare lithium batteries and power banks are written around two watt-hour thresholds. This calculator checks your result against both automatically:

mAh to Wh Converter: Airline Rules for Batteries and Power Banks
Watt-hours	Verdict	What it means
Up to 100 Wh	Carry-on approved	Allowed in the cabin with no airline approval (reasonable personal quantity).
100 – 160 Wh	Approval required	Allowed only with airline approval; maximum 2 spare batteries.
Over 160 Wh	Not allowed	Banned from carry-on and checked baggage on passenger aircraft.

Spare batteries and power banks must always travel in your carry-on, never in checked luggage. Rules can vary slightly by carrier and country, so treat this as a guide and confirm with your airline before you fly.

What Voltage Should I Use?

Use the battery's nominal voltage — the average voltage the pack holds while discharging, not the fully charged peak. Common values:

mAh to Wh Converter: What Voltage Should I Use?
Battery / device	Nominal voltage
Single Li-ion / LiPo cell, most power banks	3.6 – 3.7 V
Smartphone battery	3.85 V
2S LiPo (RC / drone)	7.4 V
Laptop battery / 3S LiPo	11.1 V
Car / lead-acid	12 V
E-bike / e-scooter	36 – 48 V
AA / AAA NiMH	1.2 V

Power Bank mAh vs Usable mAh

A 20,000 mAh battery rated at 3.7 V stores a nominal 74 Wh. With the assumed 85% conversion efficiency, estimated USB output energy is 62.9 Wh, equivalent to 12,580 mAh at 5 V. Conversion losses reduce the delivered energy; the nominal battery rating remains 74 Wh. Actual efficiency varies with the converter and load.

How to Use This Calculator

Choose a direction: mAh to Wh (the default) or Wh to mAh for the reverse.
Enter the capacity: type the mAh (or switch the unit to Ah), or the energy in Wh for the reverse direction.
Enter the voltage: type the nominal voltage, or click a battery-type preset to fill it in.
Review the result: read the watt-hour value, the airline verdict on the gauge, usable mAh at 5 V, real-world estimates, and the step-by-step formula.

Frequently Asked Questions

How do you convert mAh to Wh?

Multiply the capacity in milliamp-hours by the battery voltage, then divide by 1000: Wh = (mAh × V) / 1000. For example, a 20,000 mAh power bank at 3.7 V holds 20000 × 3.7 / 1000 = 74 Wh.

What voltage should I use for a power bank?

Most power banks rate their mAh at the internal lithium cell voltage of about 3.6 to 3.7 V, so use 3.7 V unless the label states otherwise. The 5 V printed on the USB port is the output voltage, not the rating voltage.

How many watt-hours can I take on a plane?

Spare lithium batteries and power banks up to 100 Wh are allowed in carry-on with no approval. From 100 Wh to 160 Wh you need airline approval and may carry at most 2 spares. Over 160 Wh they are banned from passenger aircraft.

Why is my usable mAh lower than the label?

How do you convert Wh back to mAh?

Multiply the watt-hours by 1000 and divide by the voltage: mAh = (Wh × 1000) / V. For example, 74 Wh at 3.7 V equals 74 × 1000 / 3.7 = 20,000 mAh.

What is the difference between mAh and Wh?

mAh (milliamp-hours) measures electric charge and depends on voltage, while Wh (watt-hours) measures energy and is voltage-independent. Wh is the fair way to compare batteries of different voltages, which is why airlines and shipping rules use Wh.

Additional Resources

Watt-hour / Kilowatt-hour - Wikipedia

Reference this content, page, or tool as:

"mAh to Wh Converter" at https://MiniWebtool.com/mah-to-wh-converter/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: July 5, 2026

Developer API available: Run this tool from your app, automation, or agent with one JSON HTTP request. View API docs

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