Electrical calculators
Testing and protection, power, cables, energy and planning. Each calculator states what it covers, shows its formula and works through your numbers.
Testing & protection
- R1 + R2Calculate R1 + R2 for standard copper conductor sizes, or from your own resistance per kilometre.
- Max ZsMaximum earth fault loop impedance for type B, C and D circuit-breakers and RCBOs in TN systems, with the value to compare test readings against.Zs ≤ U0 × Cmin ÷ Ia
- Earth fault loopAdd Ze and R1 + R2 to get Zs, then compare it with the maximum for a type B, C or D circuit-breaker or RCBO in a TN system.Zs = Ze + (R1 + R2)
- Ring finalExpected readings for the ring final cross-connection test, from the end-to-end resistances r1, rn and r2.
- Earth conductor sizeThe minimum copper protective conductor area that passes the adiabatic check, from fault current and disconnection time or from a manufacturer's let-through energy.S = √(I² × t) ÷ k
Power & current
- Ohm’s lawFind voltage, current, resistance and power in a DC resistive circuit.V = I × R
- Watts to ampsConvert electrical input power to current, with an explicit supply type.I = P ÷ (V × PF)
- kW to ampsConvert kilowatts to amps for DC, single-phase or balanced three-phase.I = kW × 1,000 ÷ (V × PF)
- Amps to kWCalculate real electrical power from current, voltage and power factor.kW = V × I × PF ÷ 1,000
- kVA ↔ kWConvert between apparent and real power using your power factor.kW = kVA × PF
- Prospective fault currentCompare line–neutral and line–earth fault-current estimates from separate loop impedances.
- Power factor correctionCalculate theoretical reactive compensation for a sinusoidal, lagging load.
- Three-phase imbalanceCompare three RMS line currents using maximum deviation from their average.
Cables & circuits
- Voltage dropCalculate voltage drop using a supplied circuit coefficient, current and route length.
- AWG to mm²Convert American Wire Gauge to nominal conductor diameter and cross-sectional area.
- Conduit cross-sectionCompare round cable cross-sectional area with a conduit’s usable internal area.
- Tray & trunking areaCompare round cable area with a specified rectangular containment cross-section.