How to convert volts to ohms

How to convert electrical voltage in volts (V) to electric resistance in ohms (Ω).

You can calculate ohms from volts and amps or watts, but you can't convert volts to ohms since volt and ohm units do not measure the same quantity.

Volts to ohms calculation with amps

According to ohm's law, the resistance R in ohms (Ω) is equal to the voltage V in volts (V) divided by the current I in amps (A):

R(Ω) = V(V) / I(A)

 

So ohms are equal to volts divided by amps:

ohms = volts / amps

or

Ω = V / A

Example

Calculate the resistance in ohms of a resistor when the voltage is 5 volts and the current is 0.2 amps.

The resistance R is equal to 5 volts divided by 0.2 amps, which is equal to 25 ohms:

R = 5V / 0.2A = 25Ω

Volts to ohms calculation with watts

The power P is equal to the voltage V times the current I:

P = V × I

The current I is equal to the voltage V divided by the resistance R (ohm's law):

I = V / R

So the power P is equal to

P = V × V / R = V 2 / R

So the resistance R in ohms (Ω) is equal to the square value of voltage V in volts (V) divided by the power P in watts (W):

R(Ω) = V 2(V) / P(W)

 

So ohms are equal to the square value of volts divided by watts:

ohms = volts2 / watts

or

Ω = V2 / W

Example

Calculate the resistance in ohms of a resistor when the voltage is 5 volts and the power is 2 watts.

The resistance R is equal to square of 5 volts divided by 2 watts, which is equal to 12.5 ohms.

R = (5V)2 / 2W = 12.5Ω

 

How to convert ohms to volts ►

 


See also

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