Ohm’s Law Calculator
Solve any one of voltage, current, resistance, or power given the other two. V = IR, P = VI.
Inputs
Voltage
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Current
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Resistance
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Power
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Energy use (continuous)
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About Ohm’s Law Calculator
Ohm’s Law in plain English
Voltage pushes current through a resistance. V = I × R. Doubling voltage on the same resistance doubles the current. Doubling resistance halves the current.
Power formulas
P = V × I (always). For purely resistive loads: P = I² × R = V² / R. AC adds power factor — real watts vs apparent VA.
Real-world sanity check
A US wall outlet is 120 V. A 1500 W heater draws 1500/120 = 12.5 A. That’s near the 15 A breaker limit, which is why hair-dryer + heater on the same circuit trips.