Watts To Ohms

Watts to Ohms Calculator

Convert power and either voltage or current to resistance in ohms.

Select either voltage or current.

How to Convert Watts to Ohms

To convert watts (W) to ohms (Ω), you need additional information—either voltage (V) or current (A)—because resistance is derived from Ohm’s Law and Power formulas. For more information on power, refer to the Wikipedia page on Watt.

Watts to Ohms Formulas

To calculate resistance (R) in ohms based on power (P) in watts, you can use one of the following formulas:

If Voltage (V) is Known:

R = V² / P
R = Resistance in ohms
V = Voltage in volts
P = Power in watts

If Current (I) is Known:

R = P / I²
R = Resistance in ohms
I = Current in amperes
P = Power in watts

Quick Trick: Use the formula that corresponds to the known value (Voltage or Current)!

Understand the Conversion

To calculate resistance in ohms from power in watts, you need either the voltage or the current:

  • If you know the voltage (V), use: R = V² / P
  • If you know the current (I), use: R = P / I²

Simply input the known values and use the appropriate formula to calculate the resistance.

Example

Imagine you have the following measurements:

  • Power entered: 36 W
  • Voltage entered: 12 V

Here’s how we figure it out:

Applying Formula:

Formula: R = V² / P

Calculation: R = (12 V)² / 36 W = 144 / 36 = 4 Ω

Answer: 4 ohms

What Do These Terms Really Mean?

Watt (W) – A Unit of Power

Watts are a standard unit of power used to measure electrical power. One watt is equal to one joule per second.

Ohm (Ω) – A Unit of Resistance

Ohms are a standard unit of resistance used to measure electrical resistance. One ohm is the resistance that allows one ampere of current to flow with one volt of electrical potential.

Author

  • Manish Kumar

    Manish holds a B.Tech in Electrical and Electronics Engineering (EEE) and an M.Tech in Power Systems, with over 10 years of experience in Metro Rail Systems, specializing in advanced rail infrastructure. He is also a NASM-certified fitness and nutrition coach with more than a decade of experience in weightlifting and fat loss coaching. With expertise in gym-based training, lifting techniques, and biomechanics, Manish combines his technical mindset with his passion for fitness.

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