Good work starts
with clear answers.
Everyday electrical calculations, with the working shown. Understand the numbers, explore the references, and find your local wholesaler.
A useful place to start.
Simple calculations. Considered details.
Choose the tool for the question in front of you.
Ohm’s law
Find voltage, current, resistance and power in a DC resistive circuit.
Watts to amps
Convert electrical input power to current, with an explicit supply type.
kW to amps
Convert kilowatts to amps for DC, single-phase or balanced three-phase.
Amps to kW
Calculate real electrical power from current, voltage and power factor.
kVA ↔ kW
Convert between apparent and real power using your power factor.
Electricity cost
Work out energy use and its cost from your own wattage and tariff.
EV charging cost
Calculate the energy charge for a session using grid-side kWh.
LED energy savings
Compare running energy and cost for two sets of lights.
Voltage drop
Calculate voltage drop using a supplied circuit coefficient, current and route length.
Prospective fault current
Compare line–neutral and line–earth fault-current estimates from separate loop impedances.
AWG to mm²
Convert American Wire Gauge to nominal conductor diameter and cross-sectional area.
Power factor correction
Calculate theoretical reactive compensation for a sinusoidal, lagging load.
Connected load
Add the electrical input power of equipment groups in watts and kilowatts.
Three-phase imbalance
Compare three RMS line currents using maximum deviation from their average.
R1 + R2
Calculate line and protective-conductor resistance from supplied resistance per kilometre.
Installation cost
Build a project subtotal from your own labour rate, materials and other costs.
Wire length
Total measured cable routes and parallel runs, with an optional length allowance.
Conduit cross-section
Compare round cable cross-sectional area with a conduit’s usable internal area.
Tray & trunking area
Compare round cable area with a specified rectangular containment cross-section.
A number is only as useful
as the assumptions behind it.
We keep our calculators focused on clearly defined arithmetic. Every tool tells you what it covers, shows its formula, and makes its limits visible.
Read our calculation methodologySee the working
Follow the calculation from your inputs to the result.
Know the boundaries
Supply type, units and assumptions are part of the answer.
Keep design decisions in context
Understand how the numbers relate to the circuit and equipment.
Beyond the calculation.
What actually determines a cable size?
A clear look at the inputs a circuit design needs.
Read the guideVoltage drop, with the context included.
Understand the cable data, circuit model and assumptions.
Read the guideFault current is more than a formula.
Why the fault path and measurement conditions matter.
Read the guide