The UK electrician's toolbox
Free BS 7671 compliant calculators for UK electricians. Cable sizing, voltage drop, max Zs, fault current and more. No sign-up required.
Essential Calculators
The tools sparkies use every day — organized by task
Circuit Design
Cable sizing, voltage drop, and circuit requirements
Testing & Verification
Loop impedance, fault current, and compliance checks
Load Calculations
Maximum demand, diversity, and load balancing
Earthing & Containment
CPC sizing, bonding, and conduit fill
Quick Converters
Unit conversions and basic formulas
Business Tools
Pricing, VAT, energy savings, and job estimating
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All calculations verified against BS 7671:2018+A2:2022 (18th Edition)
Mobile First
Designed for use on site. Large buttons, high contrast, works on any device
No Sign-Up Required
Free to use, no accounts, no faff. Just the tools you need
Trusted by UK Sparkies
SparkyHub is built by electricians, for electricians. Every calculator shows its working and references the relevant BS 7671 tables so you can verify the results yourself.