Electrician Calculator

Electrician Calculator is a pocket calculator for electricians who work to BS 7671 (UK) or NEC (US). Pick your region once, then size cables and check runs on site.

UK, labelled to BS 7671:2018+A4:2026 (Amendment 4)
• Cable sizer: enter Ib, In, reference method, ambient, grouping and length. Get the smallest cable where Iz covers In and voltage drop is within the limit.
• Voltage drop from Table 4D1B, with lighting (3%) and other uses (5%) limits
• Cable derating and current capacity from Table 4D1A with Ca, Cg and Ci

US, NEC
• Wire sizer with continuous loads, terminal ratings, 240.4(D) small conductor limits and 3% voltage drop
• Voltage drop using the K-factor method
• Wire ampacity with ambient correction and conductor adjustment
• Conduit fill and box fill

Every result shows its working. Share it, or save it to a job.

Electrician Calculator Pro is a one-time purchase that adds:
• Unlimited cable sizer (the free version includes 3 sizes)
• Every saved result, grouped by job (the free version opens the newest 3)
• PDF job reports to send or keep with your paperwork

Paths the app does not cover, such as UK conduit fill, 90°C thermosetting and aluminium Iz, twin and earth tables and earth fault loop impedance, are left out rather than guessed. Use the IET On-Site Guide and the full standards alongside the app and your own judgement on site.

Support: support@zarkon.co.uk