# What is an Ampere? What is ampere in electricity? First, let’s answer the question, “What is a current?” Current is the measure of the rate at which electrons “flow” in a circuit. Ampere is a basic unit that measures current, and is frequently shortened to “Amp.” It’s a measure of the amount of electric charge that passes a point in a circuit per unit time with 6.241 × 1018 electrons, or one coulomb per second comprising one ampere. Ampere for electric current is one of the seven SI base units, which include:

• Ampere for electric current
• Second for time
• Metre for length
• Kilogram for mass
• Kelvin for temperature
• Mole for amount of substance
• Candela for luminous intensity

## What is Ampacity?

Measured in amperes, ampacity refers to the maximum current-carrying capacity of a conductor, such as a cable, without surpassing its maximum operating temperature. How well a device can dissipate heat greatly impacts its ampacity. Current-carrying capacity is especially important when choosing a cable. Heating is the effect of current flow resistance, and the size of the conductor, the insulation material, and external factors, play a large role in current-carrying capacity and heat resistance.

Generally, the larger the conductor, the lower the current flow resistance. A larger conductor also means a greater current-carrying capacity. When the current-carrying capacity of the conductor (or a cable in this example) is high, the temperature resistance of the insulating material also needs to be high to accommodate. Insulation material with a with 190 degree F temperature rating will have a higher current-carrying capacity than insulation material rated at 150 degrees F.

## How to Calculate Watt to Ampere

You can use Watt’s Law to convert watts to amps. This formula states that I = P / E. I, or current measured in amps, equals P (power measured in watts) divided by E (voltage measured in volts). If you wanted to find the amperage of 1,200 watts at 120 volts, you would use the following formula:

• current = power / voltage
• current = 1,200W / 120V
• current = 10A

If you know the resistance of the circuit, you can convert watts to amps with the following formula:

• amps = √(watts × ohms)