Free · Built around BS 7671 · Works offline
Electrical calculators that work on site
For UK electricians and apprentices. Pick a tool, type your values, read the answer.
- V – Voltage
- I – Current
- R – Resistance
- P – Power
Most used
Voltage dropDrop in volts and % against the 3 % and 5 % limits
Cable sizeFrom device rating to twin and earth size
Maximum ZsZs limits for Type B, C and D breakers
Ohm's lawAny two of V, I, R and P
All calculators
- Ohm's lawFind voltage, current, resistance or power from any two.
- Power and currentConvert kW to amps and back, single or three phase.
- Voltage dropCheck a cable run against the 3 % and 5 % limits.
- Cable sizingTwin and earth size from device rating, install method and derating, with a voltage drop check.
- Maximum ZsEarth fault loop impedance limits for Type B, C and D breakers, with the 80 % check.
- Conduit fillHow many cables fit, using the cable factor method.
- CPC size (adiabatic)Minimum protective conductor size for a fault.
- Trunking fillCable factor method for trunking.Coming soon
- Diversity and maximum demandEstimate the load on a supply.Coming soon
Learn
All unitsLevel 2 Electrical Installation in 6 units. Worked examples and a mini test in every lesson.
Guides
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Revise for your Level 2 exams
Five packs that follow the course units, each with 50 exam-style questions and worked answers.
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Works with no signal. Use Add to Home Screen and it opens like an app, even in a plant room.