How To Calculate Milliamps

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.

Step 1

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.

Step 2

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

Step 3

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

Step 4

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

Step 5

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