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 / PIf Current (I) is Known:
R = P / I²Quick 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.
