Electrical
Tools

Enter any two of voltage, current, resistance or watts. Also turn voltage and current into kilowatts, kVA and kvar, single-phase or three-phase.

Series, parallel, or series strings in parallel branches. Add and remove resistors, and enter a supply voltage to split current and watts.

Read the bands, including tolerance, or type a resistance and see the nearest E24 colours.

Power, hours of use and your unit rate, turned into kilowatt-hours and a running cost. The sample rate is there to edit.

See how much you could save by switching to LED lighting from your current bulbs, hours and electricity rate.

Enter any of Zs, Ze, R1, R2, R1+R2, end-to-end readings or cable length. The rest is filled in to BS 7671 20°C copper values.

Current, length and conductor size for copper or aluminium, single-phase or three-phase, checked against 3% or 5%.

Minimum protective conductor size from fault current, disconnection time and k. Suggests the next standard cross-section.

kVA and kvar from real power, plus the capacitor size and the drop in line current when you raise the power factor.

Turns ratio, the missing voltage or turn count, and secondary current from primary current.

Prospective fault current from loop impedance at the origin or at the end of the circuit.

Watts or kilowatts to amps for single-phase and three-phase loads, with power factor.

Maximum length or minimum conductor size for a 3% or 5% voltage-drop limit.

How long a conductor can carry a fault current before it is below the adiabatic limit.

Measured Zs against a cautious breaker limit, or against the maximum you type in from BS 7671.

Maximum earth electrode resistance for an RCD, and the touch voltage at the residual current.

Convert a measured resistance from one conductor temperature to another.

Neutral current from three line currents, with an optional uplift for electronic loads.

A rounded-down current for a conductor size. A pass is cautious. Selection still belongs in Appendix 4.

Lighting, sockets, cookers and fixed loads, with diversity kept mean so the demand stays high.

Fill from the diameters you measure. The pass line is 35%, inside the usual space factor.

Suggests a CPC as large as the line conductor, and can show the adiabatic size alongside.