Tool

Practical calculations for GB electrical engineers, grounded in BS 7671.

Power factor, voltage drop, cable sizing, transformer calculations. Each tool references the relevant BS 7671 (18th Edition) clause or IEC standard. Inputs accept SI units; outputs show the applicable design rule. No sign-in, open to all, free to use.

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Interactive BS 7671 18th Ed. IEC standards React island Last verified

What this tool does

  • Power factor correction: compute capacitor bank size for target pf.
  • Voltage drop on cables: percentage and absolute drop for a given load and run.
  • Cable sizing: recommend conductor size to BS 7671 tables for given load and route.
  • Transformer calculations: losses, efficiency, impedance at given loading.
  • Each output cites the BS 7671 clause or IEC standard used.
Electrical engineering calculations, cable ratings and substation design

Why these tools existDesign rules save hours when they are accessible

Engineering calculations are rarely hard. Finding the right table and the right clause is the time-consuming part.

BS 7671 runs to over 500 pages. IEC 60287 (cable current ratings) is a multi-part standard. The calculations themselves are straightforward once you have the right formulas and reference tables; the time sink is looking them up. These tools bundle the most common calculations with inline references to the applicable clause.

The 18th Edition amendment 2 (effective March 2022) tightened rules on EV charging, earthing, and surge protection. The tools reflect current standards; verification dates are shown.

Which calculation do you need most often?

Open the calculator below.

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Engineering calculators

Interactive tool · Engineering calculators

References: BS 7671 (18th Edition Amendment 2), IEC 60287 for cable ratings, IEC 61439 for switchgear assemblies. Outputs cite the specific clause used.

Key takeaways

  • Four common calculations: power factor, voltage drop, cable sizing, transformer.
  • Every output cites the BS 7671 clause or IEC standard used.
  • Inputs in SI units; outputs include the applicable design rule.
  • For connection-level studies, use vendor tools (DigSilent, PSS/E).
  • For system-operator-level modelling, use LTDS data with SPARQL or rdflib.

References

  1. IET: BS 7671 18th Edition

    The main UK wiring regulation.

    Primary design standard.

  2. IEC 60287

    Cable current ratings.

    Cable sizing standard.

  3. IEC 61439

    Low-voltage switchgear assemblies.

    Switchgear standard.

Continue to the tools directory for the full list of workspace calculators and visualisations.