Electricity
Ohm's Law Calculator
Solve Ohm's law for voltage, current, resistance or power — enter any two values and get all four.
V = I × R
Also called v=ir calculator · ohms law
Science · 11 calculators
Electricity Calculators
Ohm's law, voltage, current, resistance, electrical power and energy, series and parallel resistors, voltage drop and Coulomb's law.
Electricity
Voltage Calculator
Voltage from current and resistance (V = IR) — solve for any of the three values.
V = I × R
Also called volts calculator · find voltage
Electricity
Current Calculator
Electric current from voltage and resistance (I = V/R), in amperes.
I = V / R = P / V
Also called amps calculator · amperage
Electricity
Resistance Calculator
Resistance from voltage and current (R = V/I), in ohms.
R = V / I
Also called ohms calculator · find resistance
Electricity
Electrical Power Calculator
Electrical power in watts from voltage, current or resistance, for DC and AC with power factor.
P = V × I × PF = I²R = V²/R
Also called watts calculator · power formula electrical
Electricity
Electrical Energy Calculator
Energy used by an appliance in kWh over a period, and what it costs to run.
kWh = watts × hours ÷ 1000
Also called kwh calculator · appliance energy use
Electricity
Series Resistance Calculator
Total resistance of resistors in series, with the voltage dropped across each one.
R_total = R₁ + R₂ + R₃ + …
Also called resistors in series · total resistance series
Electricity
Parallel Resistance Calculator
Equivalent resistance of resistors in parallel, with the current through each branch.
1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + …
Also called resistors in parallel · equivalent resistance
Electricity
Voltage Drop Calculator
Voltage drop along a cable run from length, conductor size and current, with the percentage drop.
V_drop = 2 × ρ × L × I / A (single phase)
Also called cable voltage drop · wire voltage loss
Electricity
Electric Charge Calculator
Charge from current and time (Q = It), in coulombs, with the number of electrons.
Q = I × t
Also called coulombs calculator · q = it
Electricity
Coulomb's Law Calculator
Electrostatic force between two point charges, with the electric field at that distance.
F = k·q₁·q₂ / r², k = 8.99 × 10⁹ N·m²/C²
Also called electrostatic force · charge force calculator
Key electricity formulas
| Ohm's Law | V = I × R · P = V × I = I²R = V²/R |
|---|---|
| Voltage | V = I × R |
| Current | I = V / R = P / V |
| Resistance | R = V / I |
| Electrical Power | P = V × I × PF = I²R = V²/R |
| Electrical Energy | kWh = watts × hours ÷ 1000 |
| Series Resistance | R_total = R₁ + R₂ + R₃ + … |
| Parallel Resistance | 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + … |
| Voltage Drop | V_drop = 2 × ρ × L × I / A (single phase) |
| Electric Charge | Q = I × t |
Electricity questions
What is Ohm's law in simple terms?
Current through a conductor is proportional to the voltage across it and inversely proportional to its resistance: I = V / R.