SparkyHub: BS 7671 Tools

Pay once. Own forever. No subscription. All BS 7671 calcs, reference tables and saved jobs = offline. Tell us what to add next inside the app.

Pay once. Own forever. No subscription. Ever.

SparkyHub is the on-site companion for UK working electricians. BS 7671 calculators, reference tables, and saved jobs — all working offline, on your phone.

The website sparkyhub.co.uk stays free, forever. This app is the paid tool for sparks who use these calcs every day, on the job, where signal is patchy and time matters.

— What's in v1 —

CALCULATORS • Voltage drop (BS 7671 Appendix 4) • Maximum Zs (Tables 41.2-41.4, 18th-edition values) • R1 + R2 with Zs compliance check • Prospective fault current (PSCC, PEFC, line-to-line) • Cable size (current capacity + voltage drop) • Ring final design (R1+R2, Zs, Vd, length) • Circuit breaker selector (Ib ≤ In ≤ Iz) • EV charger circuit (Section 722) • Conduit fill (IET cable-factor method) • Cable tray / trunking (space-factor method) • Load & demand (domestic max demand) • Diversity (On-Site Guide Appendix A) • Earthing & bonding (Table 54.7 + adiabatic)

REFERENCE • IP ratings — interactive decoder + full reference tables • Bathroom zones — Section 701 with IP, RCD, equipment per zone • Max Zs quick-reference tables (every device, every rating) • Cable current rating tables (Tables 4D5 and 4D1A)

SAVED JOBS • Save any calculation to your phone • Tap to re-open with the exact same inputs • Add customer / job notes • Share as plain text via Mail, Messages, WhatsApp

— Verified —

Every calculator has been audited against BS 7671:2018+A2:2022. The app shows the regulation each result comes from, and warns clearly when a value depends on data we have not yet confirmed against the printed standard (audit findings C03 fuses, C09 conduit factors, C14 commercial diversity).

— Anti-subscription. Anti-paywall. Anti-b******t. —

You pay once. Future BS 7671 updates are free. New calculators we add are free. There is no monthly fee, no tier, no "Pro" upgrade. Tell us what is missing inside the app and we'll add it.

If you only need the calcs once in a blue moon, use the free website at sparkyhub.co.uk/calculators. That is our deal: free online for occasional use, paid app for daily on-site.

— Designed for the loft —

Offline from launch. No account, no signup, no tracking, no analytics. Saves to your phone, not our servers. The app icon is one tap from your home screen, and the calculator you opened last is the one you opened last.

Built by an electrician's nephew, audited against the standard, made for the moment up the ladder with gloves on.