Electricity Converter
Convert between watts, amps, volts, kWh, mAh, and more.
Electricity measurements โ volts, amperes, ohms, and watts โ are interconnected through Ohm's Law and the power formula. Whether you're troubleshooting a circuit, sizing a generator, selecting a battery, or understanding your electric bill, these units and their relationships are the foundation. Messing up electrical unit conversions can mean at best a blown fuse and at worst a safety hazard.
Popular Electricity Conversions
Ohm's Law: The Foundation of Electrical Calculation
Ohm's Law states that Voltage (V) = Current (I) ร Resistance (R). This single equation connects three of the four core electrical quantities. The fourth โ power (P) โ is calculated as P = V ร I (watts = volts ร amperes). These relationships mean you can always calculate any one quantity if you know the other two: current through a 120V circuit with a 60ฮฉ load is 120 / 60 = 2 amps. Power consumed is 120 ร 2 = 240 watts. This is how electricians size wiring, fuses, and breakers.
Voltage Systems Around the World
The United States uses 120V / 60Hz for most household outlets, with 240V for high-power appliances like dryers and ovens. Europe, most of Asia, and Australia use 220โ240V / 50Hz. When traveling, voltage compatibility is critical: a device designed for 120V will be damaged or destroyed by 240V unless it has a built-in voltage converter. Many modern electronics (laptops, phone chargers) have universal 100โ240V power supplies indicated on the label. Hair dryers and flat irons are often not universal and can burn out or catch fire if used with incompatible voltage.
| Concept | Value / Formula |
|---|---|
| 1 V ร 1 A | 1 W (power) |
| 1 kWh | 1 kW drawn for 1 hour |
| 1 mAh (milliamp-hour) | 0.001 A ร 3,600 s = 3.6 C |
| US household | 120V / 240V, 60 Hz |
| EU/UK/AU | 220โ240V, 50 Hz |
| Ohm's Law | V = I ร R |
Batteries: mAh, Wh, and Real-World Capacity
Battery capacity is commonly expressed in milliamp-hours (mAh) or watt-hours (Wh). mAh measures the total charge stored; Wh measures actual energy stored. To convert: Wh = mAh ร Voltage / 1,000. A smartphone battery rated at 4,000 mAh at 3.7V stores 4,000 ร 3.7 / 1,000 = 14.8 Wh of energy. A laptop battery at 50 Wh can power a 50W laptop for about 1 hour, or a 10W system for about 5 hours. Airport regulations on lithium batteries typically use Wh limits (e.g., 100 Wh for carry-on), making Wh the more useful unit for travel compliance.
Further Reading
Sources & References
- NIST โ Units and Conversion Factors โ Official unit conversion factors from the National Institute of Standards and Technology.
- BIPM โ The International System of Units (SI) โ International SI unit definitions from the International Bureau of Weights and Measures.