Formulas & Calculators

BS 7671:2018+A4:2026 reference calculators for Cable Sizing, Earth Fault Loop (Zs), Adiabatic equation, and Ohm's Law.

Circuit Parameters

Load Power (Watts)

Voltage (V)

Length (Meters)

Tabulated mV/A/me.g. 2.5mm² = 18

Circuit Usage

Design Current (Ib)13.73 A

Min Cable Rating (Iz)13.73 A

Calculated Volt Drop6.18 V (2.69%)

Max Permissible Drop11.5 V (5%)

Voltage Drop Compliant

Within BS 7671 limits for power circuits.