mAh to Wh Calculator
A battery’s milliamp-hour rating tells you about its charge capacity, but it does not tell you the full energy capacity without the battery’s voltage. The mAh to Wh Calculator combines those two values to estimate battery energy in watt-hours (Wh). This can help you compare batteries used with dash cams, portable power supplies, and other vehicle electronics.
What the mAh to Wh Calculator does
The calculator converts battery capacity in milliamp-hours (mAh) into energy in watt-hours (Wh) using the battery’s nominal voltage. Enter the two values, and the result appears as Battery energy in Wh, rounded to two decimal places.
Milliamp-hours describe how much electric charge a battery can provide over time. Watt-hours describe energy, which takes both capacity and voltage into account. That distinction matters when you compare batteries: two batteries with the same mAh rating can store different amounts of energy if their nominal voltages differ.
For dash cam owners, watt-hours provide a useful starting point for comparing a dedicated dash cam battery pack with another battery or power source. The result is an energy estimate, though, and does not account for every loss between the battery and the camera.
How to use the mAh to Wh Calculator
Find the battery capacity and nominal voltage on the battery label, packaging, or manufacturer’s specifications. Then enter these values into the calculator:
- Battery capacity (mAh): Enter the stated capacity in milliamp-hours. For example, enter 10,000 for a 10,000 mAh battery.
- Nominal battery voltage (V): Enter the battery’s nominal voltage in volts. For example, enter 3.7 for a battery rated at 3.7 V.
- Read Battery energy: The result is shown in watt-hours, to two decimal places.
The default inputs are 10,000 mAh and 3.7 V, which produce 37.00 Wh. These values are illustrative; use the specifications for your own battery to get an estimate relevant to your setup.
If a battery lists its capacity in amp-hours (Ah) instead of mAh, multiply the Ah figure by 1,000 before entering it. For example, 5 Ah equals 5,000 mAh. Make sure the voltage and capacity describe the same battery or battery pack.
How the mAh to Wh Calculator formula works
The formula converts milliamp-hours to amp-hours and then multiplies by nominal voltage:
Battery energy (Wh) = Battery capacity (mAh) × Nominal battery voltage (V) ÷ 1,000
There are 1,000 milliamp-hours in one amp-hour. Multiplying amp-hours by volts gives watt-hours. Using the calculator’s default values:
- Battery capacity: 10,000 mAh
- Nominal battery voltage: 3.7 V
- Calculation: 10,000 × 3.7 ÷ 1,000
- Estimated battery energy: 37.00 Wh
As another example, a battery rated at 5,000 mAh and 5 V has an estimated energy capacity of 25.00 Wh. The same 5,000 mAh capacity at a different voltage would produce a different watt-hour result. If the entered capacity is zero, the calculated energy is 0.00 Wh.
Use cases for the mAh to Wh Calculator
Compare dash cam battery packs. A watt-hour figure can make it easier to compare packs with different capacity and voltage ratings. Check that each calculation uses the nominal voltage and capacity specified for the whole pack.
Assess a portable power bank. A power bank may list its internal battery capacity in mAh. Converting that rating to Wh gives you an energy estimate that can help when comparing it with other power banks. Keep in mind that its USB output voltage may differ from the internal battery’s nominal voltage.
Estimate potential operating time. If you also know a device’s average power draw in watts, you can make a rough calculation: divide the battery’s watt-hours by the device’s watts. For example, assuming a 37 Wh battery and a constant 5 W power draw, the theoretical estimate is 37 ÷ 5, or 7.4 hours. This is an illustrative assumption, not a measured dash cam runtime. Actual runtime will generally be lower because of losses and changing operating conditions.
Compare ratings across units. Some manufacturers advertise mAh, while others provide Wh. Converting to the same unit gives you a more useful basis for comparison, provided the source specifications are accurate and refer to comparable batteries.
Other factors to consider when calculating Battery energy
Use nominal voltage. Battery voltage changes as a battery charges and discharges. The calculator uses nominal voltage as a representative value, so its result is an estimate of energy rather than a measurement of every discharge cycle.
Distinguish battery voltage from output voltage. A power bank or dash cam battery pack may convert its internal battery voltage to a different output voltage. Do not automatically pair an internal-cell mAh rating with a USB or vehicle-output voltage. Look for the nominal voltage associated with the capacity rating you are entering.
Allow for conversion losses. Voltage converters and other electronics use some energy. A 37 Wh battery estimate therefore does not mean that all 37 Wh will reach a connected dash cam. Efficiency varies by equipment and operating conditions, so this calculator does not apply a fixed loss percentage.
Consider temperature, age, and discharge conditions. A battery’s available capacity can change with temperature, wear, storage, and how quickly it is discharged. The camera’s power demand can vary too, including when recording modes, accessories, or parking features change.
Check compatibility separately. A watt-hour calculation describes estimated energy capacity. It does not establish whether a battery pack’s voltage, connectors, output current, or charging method is suitable for a particular dash cam. Check the device and battery specifications before connecting them.
Frequently asked questions
How many watt-hours is 10,000 mAh?
It depends on the battery’s nominal voltage. At 3.7 V, 10,000 mAh equals 37.00 Wh. Enter the voltage specified for your battery to calculate its estimate.
Why does voltage matter when converting mAh to Wh?
Milliamp-hours measure charge capacity, while watt-hours measure energy. Voltage is needed to connect the two. Batteries with the same mAh rating but different nominal voltages have different estimated energy capacities.
Can I use this calculator for a dash cam battery pack?
Yes. Enter the pack’s capacity in mAh and the nominal voltage associated with that capacity. The result can help you compare energy ratings, but it does not by itself confirm compatibility or predict exact recording time.
Should I use the USB output voltage for a power bank?
Only use a voltage that corresponds to the capacity rating you enter. A power bank’s USB output voltage can differ from the nominal voltage of its internal battery. Check the manufacturer’s specifications when the label is unclear.
Does the watt-hour result show how much energy my dash cam can use?
It estimates the battery’s energy from its rated capacity and nominal voltage. The energy available to the dash cam can be lower because of voltage conversion losses, battery condition, temperature, and other operating factors.