Volts to mAh Calculator
Convert electrical voltage and energy storage to battery capacity in milliamp-hours (mAh). Get quick, accurate capacity estimations for 12V, 3.7V, 5V, and household electrical systems.
Volts to mAh Converter
How to Use Volts to mAh Calculator
Follow these simple steps to use the volts to mAh calculator effectively:
- 1Enter Voltage: Input the nominal voltage (V) of your battery or device (e.g., 3.7V for a cell, 12V for a car battery).
- 2Select Energy Unit: Use the dropdown next to the energy field to select your energy unit: Watt-hours (Wh), Milliwatt-hours (mWh), or Joules (J).
- 3Enter Energy Value: Input the energy capacity of the battery or system in the selected unit.
- 4Calculate: Click the Calculate to mAh button to run the conversion.
- 5Analyze Results: Read your battery capacity immediately in milliamp-hours (mAh), which represents the total electric charge capacity.
- Make sure to use the nominal voltage specified on the battery label.
- If converting from energy in Joules, remember that 1 Watt-hour equals 3,600 Joules.
- Power bank labels often specify capacity at the internal cell voltage (typically 3.7V) rather than the boosted USB output voltage (5V).
How to Calculate Volts to mAh (Conversion Guide)
To convert voltage (Volts) to battery capacity (milliamp-hours, mAh), you must understand that Volts and mAh measure two distinct physical properties: electrical potential difference and electric charge. Because of this, they cannot be converted directly without knowing the total energy capacity of the battery. This energy is typically specified in Watt-hours (Wh), Milliwatt-hours (mWh), or Joules (J).
By using the total energy, you can calculate the exact charge capacity. Doing so helps electrical engineers, device designers, and hobbyists size batteries properly for electronic systems and compare capacity ratings across different battery chemistries.
Real-Life Sizing Scenarios
Scenario 1: Sizing Smartphone Battery Capacity (3.7V Lithium-Ion)
A modern smartphone manufacturer lists their battery energy rating as 14.8 Watt-hours (Wh) at a nominal operating voltage of 3.7 Volts. To size the battery capacity in mAh, we use the standard Wh formula:
mAh = (14.8 Wh × 1000) ÷ 3.7 V = 4,000 mAh
This tells us the phone has a 4,000 mAh battery capacity.
Scenario 2: Sizing a Portable Power Station Battery (12V Lead-Acid/LiFePO4)
A camping power station or portable backup UPS is rated at 120 Wh and operates at 12 Volts. To find its capacity in milliamp-hours:
mAh = (120 Wh × 1000) ÷ 12 V = 10,000 mAh (which is equal to 10 Ah).
This helps you size standard DC loads that run off the 12V output port.
Step-by-Step Manual Sizing Guide & Formulas
To perform this calculation manually, follow these steps using the formula that corresponds to your energy unit:
mAh = (Wh × 1,000) ÷ V
mAh = mWh ÷ V
mAh = (Joules × 1,000) ÷ (V × 3,600)
Step 1: Determine your inputs. Identify the system voltage (V) and the total energy capacity. Let's assume you have a 5V USB output power bank rated at 50 Wh.
Step 2: Multiply the energy (Wh) by 1,000. This converts Watt-hours to milliwatt-hours (mWh):
50 Wh × 1,000 = 50,000 mWh
Step 3: Divide by the system voltage. Divide the mWh value by the nominal voltage (5V):
50,000 mWh ÷ 5 V = 10,000 mAh
Final Answer: The battery capacity at 5V is 10,000 mAh.
Volts to mAh Reference Conversion Chart
This table provides a quick lookup for converting standard system and battery voltages to capacity in milliamp-hours (mAh) based on common energy ratings (in Watt-hours, Wh).
| Nominal Voltage (V) | Energy Capacity (Wh) | Calculated Capacity (mAh) | Common Application |
|---|---|---|---|
| 1.2V | 2.4 Wh | 2,000 mAh | Rechargeable NiMH AA/AAA Cell |
| 1.5V | 3.0 Wh | 2,000 mAh | Alkaline AA/AAA Battery |
| 3.7V | 5.0 Wh | 1,351 mAh | Standard Lithium-Ion Cell |
| 3.7V | 11.1 Wh | 3,000 mAh | Smartphone Battery Sizing |
| 3.7V | 37.0 Wh | 10,000 mAh | Lithium Power Bank Sizing |
| 5.0V | 10.0 Wh | 2,000 mAh | Standard USB Output Power |
| 5.0V | 50.0 Wh | 10,000 mAh | USB Portable Battery Sizing |
| 7.4V | 14.8 Wh | 2,000 mAh | 2S Lithium RC battery pack |
| 9.0V | 5.0 Wh | 556 mAh | 9V Alkaline Smoke Detector cell |
| 11.1V | 44.4 Wh | 4,000 mAh | 3S Laptop/Drone Battery |
| 12.0V | 60.0 Wh | 5,000 mAh | Small Lead-Acid UPS Battery |
| 12.0V | 120.0 Wh | 10,000 mAh | Automotive Backup Battery |
| 24.0V | 240.0 Wh | 10,000 mAh | Heavy Industrial Control Sizing |
| 36.0V | 360.0 Wh | 10,000 mAh | Electric Scooter battery pack |
| 48.0V | 480.0 Wh | 10,000 mAh | Telecom solar backup battery |
12 volts to mah
A 12V voltage rating is standard for automotive lead-acid batteries, RV house batteries, boat electrical accessories, and small uninterruptible power supplies (UPS). To convert 12 volts to capacity in milliamp-hours (mAh), you need to divide the total energy capacity in Watt-hours by 12, then multiply by 1,000.
- Formula:
mAh = (Wh × 1,000) ÷ 12 - For a 60Wh Backup Battery: Sizing capacity yields
(60 × 1,000) ÷ 12 = 5,000 mAh. - For a 120Wh Car Battery: Sizing capacity yields
(120 × 1,000) ÷ 12 = 10,000 mAh(which is equal to 10 Ah).
3.7 volts to mah
A nominal potential of 3.7 Volts is the universal standard for rechargeable single-cell lithium-ion and lithium-polymer batteries. These are widely used in smartphones, tablets, rechargeable bluetooth speakers, and handheld power banks.
- Formula:
mAh = (Wh × 1,000) ÷ 3.7 - For an 11.1Wh Smartphone Battery: Capacity sizing yields
(11.1 × 1,000) ÷ 3.7 = 3,000 mAh. - For a 37Wh Lithium Power Bank: Capacity sizing yields
(37 × 1,000) ÷ 3.7 = 10,000 mAh.
1.5 volts to mah
A standard voltage rating of 1.5 Volts is common for standard household alkaline batteries (AA, AAA, C, and D sizes). These single-use batteries power low-drain devices such as TV remotes, wall clocks, and kitchen scales.
- Formula:
mAh = (Wh × 1,000) ÷ 1.5 - For a 3.0Wh Alkaline AA Battery: Capacity sizing yields
(3.0 × 1,000) ÷ 1.5 = 2,000 mAh. - For a 1.5Wh Alkaline AAA Battery: Capacity sizing yields
(1.5 × 1,000) ÷ 1.5 = 1,000 mAh.
5 volts to mah
5 Volts is the standard operating potential for USB charging grids, desktop/laptop ports, and smart accessory chargers. Converting 5V to mAh is vital when sizing capacity ratings for portable power banks or charging hubs.
- Formula:
mAh = (Wh × 1,000) ÷ 5 - For a 50Wh USB Portable Charger: Capacity sizing yields
(50 × 1,000) ÷ 5 = 10,000 mAh. - For a 25Wh Backup Battery: Capacity sizing yields
(25 × 1,000) ÷ 5 = 5,000 mAh.
48 volts to mah
A rating of 48 Volts is widely used in residential solar backup battery blocks, telecom server rooms, and light electric vehicles (LEVs) like high-speed e-bikes, electric scooters, and golf carts.
- Formula:
mAh = (Wh × 1,000) ÷ 48 - For a 480Wh Server Backup Rack: Capacity sizing yields
(480 × 1,000) ÷ 48 = 10,000 mAh(or 10 Ah). - For a 960Wh E-Bike Battery: Capacity sizing yields
(960 × 1,000) ÷ 48 = 20,000 mAh(or 20 Ah).
21 volts to mah
21 Volts is the peak charging voltage for 5-cell in series (5S) lithium battery packs. These packs are nominal 18V but are frequently marketed as "20V Max" or "21V peak" cordless power tools (like grass trimmers, leaf blowers, and drills).
- Formula:
mAh = (Wh × 1,000) ÷ 21 - For an 84Wh High-Power Power Tool Pack: Capacity sizing yields
(84 × 1,000) ÷ 21 = 4,000 mAh. - For a 42Wh Handheld Drill Battery: Capacity sizing yields
(42 × 1,000) ÷ 21 = 2,000 mAh.
220 volts to mah
220 Volts is the standard AC household single-phase voltage used across Europe, Asia, Africa, and parts of South America. Sizing capacity at 220V is useful for solar grid-tied inverters and high-voltage home battery bank backup systems.
- Formula:
mAh = (Wh × 1,000) ÷ 220 - For a 220Wh Appliance Load: Capacity sizing yields
(220 × 1,000) ÷ 220 = 1,000 mAh. - For a 1,100Wh Portable Solar Generator: Capacity sizing yields
(1,100 × 1,000) ÷ 220 = 5,000 mAh.
convert volts to mah
To convert voltage (V) to battery capacity in milliamp-hours (mAh), you must use the total active energy stored in the cell, typically measured in Watt-hours (Wh). Milliamps and volts represent distinct measurements, meaning a direct conversion requires knowing the total work capacity of the storage cell.
- Standard Sizing Formula:
mAh = (Wh × 1,000) ÷ Voltage - Alternative Sizing Formula (using Joules):
mAh = (Joules × 1,000) ÷ (Voltage × 3,600)
20 volts to mah
20 Volts is the standard high-power delivery profile for USB-C Power Delivery (PD) protocols used in modern laptops. It is also the nominal rating for mid-sized garden tool batteries.
- Formula:
mAh = (Wh × 1,000) ÷ 20 - For a 100Wh USB-C Laptop Battery: Capacity sizing yields
(100 × 1,000) ÷ 20 = 5,000 mAh. - For an 80Wh Cordless Lawn Mower Battery: Capacity sizing yields
(80 × 1,000) ÷ 20 = 4,000 mAh.
1588 volts to mah
A specific rating of 1,588 Volts represents high-voltage industrial applications. These include heavy-duty mining ventilation fans, railway traction substations, or large utility-scale battery grid arrays designed to minimize transmission current losses.
- Formula:
mAh = (Wh × 1,000) ÷ 1,588 - For a 1,588Wh Grid Backup Battery Node: Capacity sizing yields
(1,588 × 1,000) ÷ 1,588 = 1,000 mAh. - For a 3,176Wh High-Voltage Industrial Capacitor Bank: Capacity sizing yields
(3,176 × 1,000) ÷ 1,588 = 2,000 mAh.
Frequently Asked Questions (FAQs)
Milliamp-hours (mAh) measure electrical charge, while Watts (W) measure instantaneous power. If you are looking for energy capacity in Watt-hours (Wh): Wh = (mAh × V) ÷ 1,000. For a standard 3.7V internal power bank battery, 20,000 mAh is equal to (20,000 × 3.7) ÷ 1,000 = 74 Wh. At 5V output, it represents 100 Wh of energy.
One Volt (V) is defined as the difference in electrical potential that will force a current of 1 Ampere (A) through a conductor with a resistance of 1 Ohm (Ω). It is also equal to 1 Joule of electrical energy per Coulomb of charge (1 V = 1 J/C).
Ampere-hours (Ah) and milliamp-hours (mAh) are related by a factor of 1,000. To convert Ah to mAh, multiply the Ah value by 1,000: 100 Ah × 1,000 = 100,000 mAh.
One milliampere-hour (1 mAh) is equal to 0.001 Ampere-hour (Ah). It represents the amount of electrical charge transferred by a steady current of 1 milliampere flowing for a duration of exactly 1 hour. It is also equal to 3.6 Coulombs of charge.
Almost all commercial 20,000mAh power banks contain internal lithium-ion cells with a nominal voltage of 3.7 Volts. When supplying power, the internal circuitry boosts this voltage to standard USB outputs of 5 Volts, 9 Volts, 12 Volts, or 20 Volts depending on fast-charging standards.
Watts measure power rate, whereas mAh measures charge capacity. If you mean energy in Watt-hours (Wh), you can convert it using: Wh = (mAh × V) ÷ 1,000. For a standard 3.7V cell, 2,000 mAh is equivalent to (2,000 × 3.7) ÷ 1,000 = 7.4 Wh. For a 1.2V rechargeable NiMH cell, it is 2.4 Wh.
A 20,000mAh battery has twice the capacity of a 10,000mAh battery, allowing it to charge your devices twice as many times. However, a 20,000mAh battery is heavier, physically larger, and takes longer to charge. Choose 10,000mAh for daily portability and 20,000mAh for long trips or multiple devices.
A 20,000mAh battery is an energy storage system that can deliver a total of 20,000 milliamp-hours of electric charge. For instance, it can sustain a current draw of 20,000 mA (20A) for 1 hour, or a draw of 1,000 mA (1A) for 20 hours, before running flat.
The lifespan of a charge depends on the current draw of your device: Hours = Capacity (mAh) ÷ Draw (mA). If your phone draws 500mA during active use, a 10,000mAh battery will last: 10,000 mAh ÷ 500 mA = 20 hours. If the load draws 1,000mA (1A), it will last 10 hours.
Watts measure power rate, not total capacity. If you mean 1 Watt-hour (1 Wh) of energy, the capacity in mAh depends on the system voltage: mAh = (Wh × 1,000) ÷ V. At 3.7V, 1 Wh equals 270.3 mAh. At 5V, 1 Wh equals 200 mAh. At 12V, 1 Wh equals 83.3 mAh.