Free Electrical Calculatorsfor UK Electricians
BS 7671 compliant calculators — cable sizing, voltage drop, load, Zs & more. No signup required.
Featured Calculators
The eight most-used calculators, from cable sizing to ring final verification.
Cable Size Calculator
Calculate correct cable sizes for BS 7671 compliance
Voltage Drop Calculator
Check voltage drop meets BS 7671 limits for any circuit
Load Calculator
Calculate electrical loads with UK diversity factors
Max Zs Calculator
Verify earth fault loop impedance for protective devices
PFC Calculator
Calculate prospective fault current at any point
Earthing & Bonding
Size earthing and bonding conductors to BS 7671
Ring Final Circuit
Verify ring final circuit continuity test results
Diversity Calculator
Apply diversity factors for maximum demand calculations
Browse by Category
Find the right calculator for your project. Tools organised by use case.
BS 7671 Compliance
Zs, PFC, earthing & circuit protection calculators
Cable & Wiring
Cable sizing, voltage drop & conduit fill tools
Testing & Verification
Ring final, Zs verification & test result tools
Design & Planning
Load, diversity, EV charger & solar sizing tools
Why electricians use these tools
Built for working electricians who need fast, accurate calculations on-site.
BS 7671:2018+A2:2022
Calculations follow the 18th Edition wiring regulations, with the relevant regulation or table referenced
Free, no signup
No account, no email, no paywall. Open a tool and start calculating
Built for site work
Big touch targets and phone-first layouts — usable one-handed in the van or at the board
Shows its working
Full calculation breakdowns you can reference in certificates and reports
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Find the right calculator for your project
51 free BS 7671 calculators for cable sizing, voltage drop, load calculations and more.