Electrical Calculators
Free online calculators for BS 7671 IET Wiring Regulations. Designed for UK electricians, engineers, and designers — no downloads required.
22
Calculators
5
Categories
BS 7671
Compliant
Free
Always
Cable Sizing & Selection
Calculate cable sizes, voltage drop, R1+R2 values, conduit fill capacity, and temperature-adjusted resistance for BS 7671 compliance.
Protection & Fault Analysis
Verify earth fault loop impedance, prospective fault current, protective conductor sizing, and device selection to BS 7671.
Load & Demand
Assess maximum demand with diversity factors, balance three-phase loads, correct power factor, and convert electrical units.
Circuit-Specific
Dedicated calculators for ring finals, EV charger installations, motor circuits, solar PV, and earthing & bonding sizing.
Design & Reference
Lighting design tools for lux levels and downlight spacing, plus IP rating and bathroom zone reference guides.
About These Calculators
Built for BS 7671
All calculators use formulas, tables, and correction factors from the IET Wiring Regulations (BS 7671:2018+A2:2022) and the IET On-Site Guide. Results are for guidance — always verify against the full regulations for your specific installation.
Works Everywhere
These calculators run entirely in your browser — no app downloads, no sign-ups, no internet needed after the page loads. Use them on-site from your phone, tablet, or laptop.
Study for the 18th Edition Exam
Complement your practical calculations with exam prep. Our app has 800+ practice questions with detailed explanations covering all parts of BS 7671.
