Enter the resistance (ohms), the current (amps), and the voltage drop (volts) into the calculator to determine the Source Voltage. 

Source Voltage Formula

The following formula is used to calculate the Source Voltage.

Vs = R*I + Vd
  • Where Vs is the Source Voltage (volts)
  • R is the resistance (ohms) 
  • I is the current (amps) 
  • Vd is the voltage drop (volts) 

To calculate the source voltage, multiply the resistance by the current, then add the voltage drop.

How to Calculate Source Voltage?

The following example problems outline how to calculate Source Voltage.

Example Problem #1

  1. First, determine the resistance (ohms). In this example, the resistance (ohms) is determined to be 4 .
  2. Next, determine the current (amps). For this problem, the current (amps) is measured to be 5 .
  3. Next, determine the voltage drop (volts). In this case, the voltage drop (volts) is found to be 20.
  4. Finally, calculate the Source Voltage using the formula above: 

Vs = R*I + Vd

Inserting the values from above and solving the equation yields: 

Vs = 4*5 + 20 = 40 (volts)

Example Problem #2

Using the same method as above, determine the variables required by the equation. For this example problem, these are:

resistance (ohms) = 3

current (amps) = 6

voltage drop (volts) = 30

Enter these given values into the calculator or above yields: 

Vs = 3*6 + 30 = 48 (volts)