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UK BS 7671 Cable Size, Current Carrying Capacity & 3% Voltage Drop Calculator

Determine Twin & Earth (T&E) copper conductor size (1.5mm² to 16mm²) ensuring voltage drop stays below statutory 3% (lighting) and 5% (power).

Parameters & Dimensions

UK Building & Trade Guidelines:

    How to Use This Calculator

    1. Input your dimensions and structural/electrical parameters into the fields above.
    2. Review the instantly calculated material quantities, safety margins, and cost estimations.
    3. Download or print the bill of materials (BOM) for your trip to B&Q, Screwfix, or local builders merchant.

    Frequently Asked Questions (UK Regulations)

    How accurate is this UK BS 7671 Cable Size, Current Carrying Capacity & 3% Voltage Drop Calculator?

    Calculations comply directly with UK Building Regulations, BS standards (such as BS 7671 for electrical and BS 5268 for timber), incorporating customary 5-15% wastage allowances.

    Can I use this for planning permission or building control submissions?

    Yes, our algorithms follow approved statutory formulas and provides accurate guidance; however, always have critical structural work countersigned by a qualified structural engineer or Building Control officer.

    Does this support both metric and imperial units?

    Yes, while UK Building Regulations specify metric (metres, mm, kg), you can easily cross-reference standard timber sections (e.g., 4x2 inches as 100x47mm).