Voltage Calculator

Use the voltage calculator below to calculate the voltage given the current, power, or resistance.

Current:

milliampsampskiloamps

Resistance:

milliohmsohmskiloohms

Power:

milliwattswattskilowatts

Voltage:

millivoltsvoltskilovolts

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By

Joe Sexton

Joe is the creator of Inch Calculator and has over 20 years of experience in engineering and construction. He holds several degrees and certifications.

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Reviewed by

Aditya Dua, PhD

Aditya holds a PhD in electrical engineering from Stanford University and specializes in signal processing, algorithms, and machine learning.

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Cite As:

Sexton, J. (n.d.). Voltage Calculator. Inch Calculator. Retrieved April 17, 2025, from https://www.inchcalculator.com/voltage-calculator/

How to Calculate Voltage From Power and Resistance

Voltage is the potential difference between two points in an electrical circuit, measured in volts. In a static electric field, it is the measure of the work needed to move a unit of electric charge between two points.

You can calculate the voltage in a circuit using Ohm’s Law, which states that the current through a circuit element is directly proportional to the potential difference applied to it and inversely proportional to the resistance.^[1]

Voltage Formula

The Ohm’s Law formula states I = V/R, where I is the current through the circuit (in amperes or amps), V is the potential difference across the circuit (in volts), and R is the resistance of the circuit (in ohms).^[2]

By rearranging this formula, you can calculate the voltage by multiplying the current flowing through a circuit by the resistance of the circuit. The formula to calculate voltage is:

V = I × R

Thus, the voltage (or potential difference) V across the circuit is equal to the product of the current I flowing through the circuit and the resistance R of the circuit.

This is the formula that is used to convert amps to volts.

How to Calculate the Voltage From Power

You can also calculate the voltage in a circuit using Watt’s Law power formula. If you know the power in watts drawn through a circuit and the current in amps, the formula to calculate the voltage is:

V = P / I

The voltage (or potential difference across) V of the circuit is equal to the power P drawn through the circuit divided by the current I flowing through the circuit.

This is the formula that is used to convert watts to volts.