Ohm's law calculator
Enter the two known quantities from voltage, current, resistance and power, and we calculate the other two.
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How does the Ohm's law calculator work?
Ohm's law relates voltage (U), current (I), resistance (R) and power (P). From any two of the four quantities the other two can be calculated:
- U = I · R, I = U / R, R = U / I
- P = U · I = I² · R = U² / R
Enter the two known quantities and we calculate the other two. If you want to change a value you have already filled in, clear the field first, because the calculator expects exactly two values.
What to use it for
The power from the resistance of a heating element, the current or the resistance from the power and voltage of a load: it is good for a quick check when you do not have all the rating-plate data at hand. For a DC or resistive AC load the resistance gives the exact value; for a motor or compressor the power factor must also be taken into account, so use the power and current converter for that.
Frequently asked questions
Which two quantities can I calculate from?
Any two of the four quantities (voltage, current, resistance, power): six pairings are possible in all.
Can I use it for an AC motor?
For a resistive load, yes. For a motor and other inductive loads the power factor must also be taken into account; the power and current converter is for that.
Related pages
- Power and current converter – on single- and three-phase networks, with cos φ
- Energy cost calculator – consumption and cost
- Electrician calculators – all the calculators
In detail in the tutorial
- Distribution boards, single-line diagram and sizing – the operating current in the circuits