Electrical Calculator · Instrument Apps Hub

Enter any two values

Voltage VV Current IA Resistance RΩ Power PW

V = I·R P = V·I = I²·R = V²/R Tip for 4–20 mA loops: 20 mA through a 250 Ω resistor gives 5 V and 0.1 W.

Resistor values (Ω)

Separate with commas or spaces. k and M allowed (4.7k, 1M).

Series: R = R1 + R2 + … Parallel: 1/R = 1/R1 + 1/R2 + …

Input voltage VinV R1 (top)Ω R2 (bottom)Ω Wanted VoutOptional: finds R2 for this outputV

Vout = Vin · R2 / (R1 + R2) (no load on the output)

System Supply voltageLine-line for 3-phaseV Load currentA Cable length (one way) Conductor size Material Conductor temperature Allowed drop%

R = ρ·(1 + α(T − 20))/A per metre of conductor DC and 1-phase: ΔV = 2·L·I·R 3-phase: ΔV = √3·L·I·R ρ20: Cu 0.017241, Al 0.028264 Ω·mm²/m; α: Cu 0.00393, Al 0.00403 /K Reactance is ignored: fine for small cables; for large AC cables use the cable maker's mV/A/m data.

Supply VoltageLine-line for 3-phaseV Power factor cos φ EfficiencyFor motor shaft power; 100 % = electrical only% Known value

3-phase: S = √3·V·I 1-phase: S = V·I P = S·cos φ Q = S·sin φ Shaft power = P·η 1 hp = 0.7457 kW