The mAh to Wh Calculator converts a battery capacity in milliamp-hours into watt-hours using the battery's matching nominal voltage. Enter any positive mAh value and voltage to see Wh, Ah, kWh, and joules instantly, with a formula breakdown you can verify by hand.
Use it for phone batteries, power banks, camera packs, lithium cells, LiFePO4 cells, drones, portable electronics, and other batteries where capacity is printed in mAh but energy comparisons are easier in Wh.
Enter the capacity and the nominal voltage that belong to the same battery rating. The calculator applies Wh = mAh × V ÷ 1000 and shows the related energy values.
Use the battery label or manufacturer datasheet for voltage. Do not substitute a charger's output voltage unless that is also the rated battery voltage.
Nominal battery energy calculated from the entered mAh and voltage.
Equivalent amp-hour capacity after dividing milliamp-hours by 1000.
The same nominal energy expressed in kilowatt-hours for larger comparisons.
Energy in joules, using 1 watt-hour = 3600 joules.
The conversion is short, but using the right voltage is essential. These concepts explain what each number represents and why watt-hours are usually better for comparing stored energy.
The mAh to Wh Calculator is useful because milliamp-hours describe electrical charge, while watt-hours describe energy. A battery's mAh rating by itself does not tell you the complete energy content. Voltage must also be known. A 10,000mAh battery at 3.7V contains 37Wh nominally, while the same 10,000mAh rating at 7.4V represents 74Wh.
This distinction matters when comparing batteries across devices. Phones, cameras, drones, laptops, power banks, and larger packs may use different cell counts or chemistries. If you only compare mAh, a lower-voltage battery can appear larger even when it stores less energy. For broader unit conversions, the Battery Capacity Calculator helps compare Ah, Wh, and related ratings.
Milliamp-hours indicate charge capacity. The prefix “milli” means one-thousandth, so 1000mAh equals 1Ah. NIST lists milli as the SI prefix for 10−3, which is why the conversion from mAh to Ah uses division by 1000.
Convert mAh to AhWatt-hours represent energy. They combine capacity and voltage, making Wh a more useful number for comparing batteries that operate at different nominal voltages.
Open the Watt Hour CalculatorVoltage is the missing factor when converting charge into energy. The mAh number and voltage must describe the same battery or pack. Check the label or datasheet rather than guessing from the charger or USB output.
Check lithium voltage referencesIf you already know watt-hours and voltage, reverse the equation to estimate milliamp-hours. That is useful when comparing product labels that publish energy instead of capacity.
Convert Wh to mAhThe mAh to Wh Calculator uses a direct electrical relationship. Understanding the three steps makes it easy to check a result without relying on any tool.
The core formula is Wh = (mAh × V) ÷ 1000. First, milliamp-hours are converted to amp-hours by dividing by 1000. Then amp-hours are multiplied by voltage. The U.S. Federal Aviation Administration explains the same method when determining a lithium-ion battery's watt-hour rating: convert mAh to Ah, then multiply by volts.
For 10,000mAh at 3.7V, the calculation is 10,000 × 3.7 ÷ 1000 = 37Wh. The mAh to Wh Calculator also shows 10Ah, 0.037kWh, and 133,200 joules. Those are different expressions of the same nominal rating, not extra energy.
If you need a more general energy conversion after this step, the Watt Hour Calculator can help with watts, time, and energy relationships. If you are starting from Wh and need Ah instead, use the Wh to Ah Calculator.
The most common conversion mistake is combining a battery's mAh rating with the wrong voltage. The capacity and voltage should describe the same electrical level. A power bank, for example, may advertise cell capacity near the cell's nominal voltage while its USB port outputs a different voltage through conversion electronics.
Using 5V with a mAh rating that was specified at 3.7V would overstate the stored energy. For accurate label conversion, use the nominal voltage tied to the battery capacity. When in doubt, check the manufacturer's technical data rather than inferring voltage from the connector.
The conversion gives nominal watt-hours from label ratings. Real delivered energy can be lower because of conversion losses, protection cutoffs, temperature, aging, load level, and the usable discharge range allowed by the battery management system.
That distinction is important when estimating runtime. After converting with the mAh to Wh Calculator, use a runtime model that includes efficiency assumptions rather than expecting every nominal watt-hour to reach the load.
When compatible cells are connected in series, pack voltage increases while the amp-hour capacity of the series string stays the same. A two-cell lithium-ion pack may therefore have roughly twice the nominal voltage of one cell while retaining the same Ah rating.
This is why 5000mAh at 7.4V is not the same energy as 5000mAh at 3.7V. The first converts to 37Wh; the second converts to 18.5Wh. If you are designing a multi-cell pack, the Battery Cell Configuration Calculator can help organize series and parallel relationships.
In a compatible parallel arrangement, voltage stays the same while amp-hour capacity adds. Two equal 3000mAh cells in parallel can be treated as 6000mAh at the same nominal voltage for basic energy arithmetic, subject to the pack's actual design and manufacturer limits.
For pack-level planning, confirm whether the published rating already describes the complete pack. Entering per-cell mAh with pack voltage can overstate Wh when the cells are arranged in series.
| Capacity | Nominal Voltage | Calculation | Nominal Energy | Example Context |
|---|---|---|---|---|
| 1000mAh | 3.7V | 1000 × 3.7 ÷ 1000 | 3.7Wh | Small single-cell lithium pack |
| 3000mAh | 3.7V | 3000 × 3.7 ÷ 1000 | 11.1Wh | Phone-size battery example |
| 5000mAh | 3.7V | 5000 × 3.7 ÷ 1000 | 18.5Wh | Larger portable-device battery |
| 10,000mAh | 3.7V | 10,000 × 3.7 ÷ 1000 | 37Wh | Common power-bank rating example |
| 20,000mAh | 3.7V | 20,000 × 3.7 ÷ 1000 | 74Wh | Large power-bank example |
| 26,800mAh | 3.7V | 26,800 × 3.7 ÷ 1000 | 99.16Wh | Near-100Wh example |
| 10,000mAh | 3.2V | 10,000 × 3.2 ÷ 1000 | 32Wh | LiFePO4 nominal-cell example |
The mAh to Wh Calculator is mathematically simple, so most errors come from the inputs rather than the equation. The first mistake is treating every lithium battery as 3.7V. Many lithium-ion cells are labeled around 3.6V or 3.7V, some higher-voltage variants use different nominal ratings, and LiFePO4 cells commonly use a lower nominal voltage. A small difference in voltage changes the Wh result directly, so the label value should win over a generic chemistry preset.
The second mistake is mixing a cell rating with a pack rating. Suppose a pack contains cells in series. The complete pack voltage is higher than one cell's voltage, but the series string does not add the Ah rating in the same way a parallel connection does. If a manufacturer publishes capacity for the finished pack, use the finished pack's mAh and nominal voltage together. If you are building a battery bank, confirm the series/parallel arrangement before making the conversion.
A third mistake is using charging voltage instead of nominal voltage. A lithium battery may charge to a voltage above its nominal rating, but the mAh capacity is normally paired with the nominal battery voltage for energy labeling. Multiplying mAh by the maximum charge voltage will usually produce a number that is not the intended nominal Wh rating. The lithium battery charging guide explains why charging setpoints and nominal voltage serve different purposes.
Finally, do not interpret the Wh conversion as a guaranteed runtime figure. A battery labeled 37Wh will not necessarily deliver 37Wh to a USB device, inverter, motor, or radio. Electronics consume some energy during conversion, and batteries can stop discharging before every nominal watt-hour is available. Use the mAh to Wh Calculator for clean unit conversion, then apply efficiency, reserve, load behavior, and manufacturer limits in the next stage of system planning.
Accuracy and safety note: This calculator performs a rating conversion; it does not predict exact runtime, remaining state of charge, safe charging voltage, maximum current, or whether a battery is suitable for a specific device. Always follow the battery and equipment manufacturer's specifications.
For U.S. air travel, the FAA currently uses watt-hour ratings when describing lithium-ion battery limits and notes that airline rules may be more restrictive. Check the current FAA airline passenger battery guidance and your carrier before travel. For the SI meaning of “milli,” see the NIST metric prefix reference.
These worked examples show how the same formula behaves at different capacities and voltages, and why matching the correct voltage to the mAh rating matters.
10,000mAh ÷ 1000 = 10Ah. Multiply 10Ah × 3.7V to get 37Wh. This is the nominal stored-energy figure for the rating pair. It should not be confused with energy delivered at a 5V USB output, because conversion losses occur between the internal battery and the output port.
3000 × 3.85 ÷ 1000 = 11.55Wh. Notice that using 3.85V instead of 3.7V changes the result. The correct input is the nominal voltage printed for that specific battery, not a universal number for all lithium-ion cells.
6000 × 6.4 ÷ 1000 = 38.4Wh. If the label already states 6.4V for the pack, use that pack voltage with the pack's 6000mAh rating. Do not substitute the nominal voltage of one 3.2V cell unless the capacity rating also refers to a single cell.
Once you know watt-hours, you can compare batteries on a common energy basis, estimate runtime against a load, or check whether two products with different mAh ratings actually store similar energy. The Battery Runtime Calculator is the next logical step when you know the device wattage. For larger solar or backup planning, use the Battery Sizing Calculator instead of treating a simple mAh conversion as a complete system design.
If you are comparing lithium chemistries rather than only units, the LiFePO4 vs Li-ion guide explains why nominal voltage, safety characteristics, and application fit can differ even when battery energy is expressed in the same Wh unit.
Answers to common questions about the mAh to Wh Calculator, voltage selection, battery labels, power banks, and interpreting the result.
Multiply milliamp-hours by the battery's nominal voltage and divide by 1000. The formula is Wh = mAh × V ÷ 1000. For example, 5000mAh at 3.7V equals 18.5Wh. The mAh to Wh Calculator performs exactly this conversion and also shows the equivalent Ah, kWh, and joules.
No. mAh is a charge-capacity value, while Wh is an energy value. Voltage is required to connect the two. If voltage is missing, check the battery label, pack specification, or manufacturer datasheet. Guessing voltage can produce a misleading energy result.
No. It is 37Wh only when the matching nominal voltage is 3.7V. At 3.2V, 10,000mAh is 32Wh; at 7.4V, it is 74Wh. That is why the voltage field is required and why mAh alone should not be used to compare batteries at different voltages.
Use the voltage that corresponds to the published mAh rating. Many power banks state capacity based on internal lithium cells while delivering power through a regulated USB output. If the mAh rating is tied to the internal cell voltage, using 5V would not be a like-for-like conversion. Check the product specification when the label is unclear.
Wh includes both capacity and voltage, so it represents energy. Two batteries can have the same mAh rating but very different Wh ratings if their voltages differ. Wh therefore provides a more meaningful basis for comparing batteries across different pack voltages.
Not necessarily. The result is nominal energy based on label ratings. Real usable energy may be lower because of conversion losses, low-voltage cutoffs, temperature, aging, discharge rate, and protection settings. Use product-specific data when runtime or safety is important.
Yes. The calculator accepts positive decimal values for both mAh and voltage. This is useful when a datasheet lists values such as 3150mAh, 3.85V, or other non-integer ratings. Results are formatted to preserve useful precision without displaying unnecessary trailing zeros.
Use mAh = Wh × 1000 ÷ V. The site's Wh to mAh Calculator applies that reverse formula. You still need voltage because the same Wh can correspond to different mAh values at different voltages.
Use the mAh to Wh Calculator with the capacity and nominal voltage from your battery label, then carry the Wh result into runtime, charging, or battery-sizing calculations for a clearer energy comparison.
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