20 tools
Electrical Engineering Tools
Twenty browser-based electrical calculators: power and power factor, cable and busbar sizing, voltage drop, fault level, breakers and fuses, transformers, motors and starters, load schedules and demand.
About these tools
Every calculator here asks one question before it computes anything: are you working to IEC or to NEC? The two bodies of rules use different conductor series, different derating tables and different rounding conventions, and a result that does not say which one it used is worse than no result at all. Each page shows the tables and factors it applied, so you can check the working against your own copy of the standard.
These pages are design aids, not approvals. A calculation cannot see your installation method, your ambient conditions, the protective device you actually have on the shelf or the amendments your local regulations add. Treat every figure here as indicative, and have a qualified engineer verify the design against the applicable standard and local rules before anything is installed or energised. Nothing you type is uploaded - the maths runs in your browser.
Popular tasks
All Electrical Engineering Tools
- Single-Phase Power Calculator Work out single-phase real power, apparent power, reactive power, current or voltage from any two known values, with the power triangle, the phase angle and the formula used shown in full.
- Three-Phase Power Calculator Convert between three-phase kW, kVA, kVAr and line current for balanced loads, in star or delta, with line and phase voltages and currents shown separately and the root-three relationship spelled out.
- Power Factor Correction Calculator Size the capacitor bank needed to move a load from its present power factor to a target one: required kVAr, capacitance per phase, released transformer capacity, current reduction and a suggested step arrangement.
- Electrical Cable Size Calculator Size a circuit conductor under IEC or NEC rules: design current, the derating factors for grouping, ambient temperature, insulation and installation method, the required current-carrying capacity and the smallest cable that meets it.
- Voltage Drop Calculator Calculate voltage drop along a run in volts and per cent, for copper or aluminium, single or three phase, with conductor resistance corrected for operating temperature and the maximum acceptable length for your drop limit.
- Short-Circuit Current Calculator Estimate prospective short-circuit current at a board from transformer rating and impedance, source fault level and cable impedance, so you can compare it with the breaking capacity of the devices you plan to fit.
- Circuit Breaker Size Calculator Choose a protective device rating for a circuit: design current, the next standard frame size, the coordination check against cable capacity, a suggested tripping curve for the load type and the breaking capacity the fault level demands.
- Electrical Fuse Size Calculator Pick a fuse rating for a cable or a motor circuit: the standard rating above design current, the gG or aM utilisation category, discrimination with the upstream fuse and the cable protection check the standards require.
- Transformer kVA Calculator Size a distribution transformer from connected load, diversity, power factor, future growth and the loading limit you want to keep, then see the standard kVA rating above the requirement and how hard it would run.
- Transformer Current Calculator Convert a transformer rating into primary and secondary full-load current for single-phase or three-phase units, with the turns ratio, the current at any loading percentage and the inrush and fault current estimates from %Z.
- Motor Full-Load Current Calculator Turn a motor's kW or horsepower rating into full-load current for single-phase or three-phase supplies, using the efficiency and power factor you enter, and see input kW, kVA and current at part load.
- Motor Starting Current Calculator Compare motor starting current and torque across direct-on-line, star-delta, autotransformer and soft starting: the inrush multiple, the starting kVA, the torque you keep and the voltage dip the supply is likely to see.
- Motor Slip Calculator Work out synchronous speed from poles and frequency, slip in rpm and per cent from measured shaft speed, rotor frequency, and what the numbers suggest about loading on an induction motor.
- Star-Delta Starter Calculator Size the three contactors and the overload relay for a star-delta starter, with the line and winding currents each one carries, the starting current and torque compared with direct-on-line, and a changeover time to start from.
- Electrical Load Schedule Builder Build a panel load schedule circuit by circuit: connected load, power factor, demand factor and phase allocation, with per-phase totals, imbalance, the diversified demand and a printable schedule you can export.
- Generator Fuel Consumption Calculator Estimate diesel or petrol consumption for a generating set from its rating and load factor: litres or gallons per hour, run time from tank capacity, fuel cost per hour and per kWh, and consumption across the load range.
- Electrical Conduit Fill Calculator Check how full a conduit or trunking is: total conductor cross-section against the permitted fill percentage for the number of cables, the smallest conduit that complies, and the spare capacity left for future circuits.
- Earthing Conductor Size Calculator Size protective earthing and bonding conductors: the table method against the phase conductor, the adiabatic equation from fault current and disconnection time, and the larger of the two with the k value used shown.
- Electrical Busbar Size Calculator Estimate the current a copper or aluminium busbar can carry: cross-section, current density, the derating for bar arrangement and enclosure temperature, plus resistance, losses and volt drop along the run.
- Electrical Demand Factor Calculator Turn a list of connected loads into a maximum demand figure: demand and diversity factors per load group, the coincident peak, load factor over a period, and the supply capacity the result implies.
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