# How to Calculate Milliamps ••• Photos.com/Photos.com/Getty Images

Ohm's Law is the basic formula for electronics. With it, we may calculate Resistance (Ohms), Voltage (Volts) or Current (Amps) by knowing any two of the three values.

## How to Calculate Milliamps

A milliamp is one one-thousandth of an amp. By calculating the value in amps and dividing by one thousand, you will have a value of current in milliamps.

Ohm's Law is Voltage = Resistance X Current. The derivations are: Resistance = Voltage / Current Current = Voltage / Resistance

Calculate Current using your known Voltage and Resistance as shown in Step 2. Current (I) = Voltage (V) divided by Resistance (R) I = V/R Ex: if your voltage is 12V and resistance is 200 Ohms I = V/R = 12 / 200 = 0.06 Amps

Knowing your Current in Amps, multiply by 1000 to see the value in milliamps Ex: 0.06 Amps x 1000 = 60 milliamps

Given a known Voltage and Current, you may also derive Power (Watts). Power = Voltage times Current ( P = V x I ) Ex: 12V x 0.06A = 0.72W or 720 milliwatts

#### Things You'll Need

• Known voltage value
• Known resistance value