⚡ Cable Size Calculator

BS7671 18th Edition • Full Correction Factors • Voltage Drop

Amendment 2:2022

📋 Circuit Details

Circuit Type

Ring

Radial

Lighting

Cooker

Shower

Design Current (Ib) A

Protective Device (In) A

Cable Length m

Supply Voltage

🔌 Cable Type

Cable

Installation Method BS7671

🌡️ Correction Factors

Ambient Temp Ca

Grouped Cables Cg

Thermal Insulation Ci

Fuse Type Cf

Combined Factor: 1.00

Required Iz = In ÷ factors = 32.00 A

📊 Results

Recommended Cable Size

2.5mm²

Twin & Earth (6242Y)

Current (It)

27 A

Required (Iz)

32 A

Voltage Drop

3.2%

VD (Volts)

7.4 V

✓ Current OK ✓ VD OK

Parameter	Value	Limit	Status

📝 Notes

Size	It (A)	mV/A/m	VD %	Status

📖 Quick Reference

Lighting1.0mm² / 6A

Ring Final2.5mm² / 32A

Radial 20A2.5mm² / 20A

Radial 32A4.0mm² / 32A

Cooker6-10mm² / 32-45A

Shower 8.5kW6.0mm² / 40A

Shower 10.5kW10mm² / 50A

EV 7kW6.0mm² / 32A

Lighting3% (6.9V)

Other5% (11.5V)

📉 Voltage Drop Calculator

Calculate VD for known cable size

Cable Size mm²

Current A

Length m

Phase

📊 Result

Voltage Drop

0% of supply

Status

mV/A/m

At Load

230 V

📊 Twin & Earth (6242Y) - Current Capacity

BS7671 Table 4D5

mm²	Method A	Method B	Method C	mV/A/m
1.0	11	13	15	44
1.5	14	16	19.5	29
2.5	18	22	27	18
4.0	24	30	37	11
6.0	31	38	47	7.3
10.0	42	52	65	4.4
16.0	56	69	87	2.8
25.0	73	90	114	1.75

🌡️ Temperature Factors (Ca)

°C	25	30	35	40	45	50
70°C PVC	1.03	1.00	0.94	0.87	0.79	0.71

📦 Grouping Factors (Cg)

Circuits	1	2	3	4	5	6
Cg	1.00	0.80	0.70	0.65	0.60	0.57