Wire Length Calculator

Calculate total cable lengths and quantities for electrical installations in the UK

Wire Length Calculator

Calculate total cable length and quantities for your project

Select project type for quick setup

m
m
m
m

Average distance from circuits to consumer unit

%

Recommended: 10-15% for unforeseen routing changes

Circuits

m
m

How to Use the Wire Length Calculator

This calculator helps you accurately estimate the total amount of cable needed for electrical installations, reducing waste and ensuring you order the right quantities.

Step 1: Project Setup

  • Enter room dimensions (length, width, ceiling height)
  • Select installation method (surface, buried, conduit, etc.)
  • Specify distance to consumer unit
  • Set waste factor (recommended 10-15%)

Step 2: Add Circuits

  • Click "Add Circuit" for each circuit type (lighting, sockets, etc.)
  • Select appropriate cable size for each circuit
  • Enter number of points (sockets, lights, etc.)
  • Specify average spacing between points
  • Choose routing method (straight, perimeter, custom)

Step 3: Review Results

  • Check total cable length with waste factor applied
  • Review cable type breakdown and drum requirements
  • Use shopping list for ordering materials
  • Note estimated costs (approximate wholesale prices)

Understanding the Results

Total Cable Needed: Calculated length before waste factor

Order Quantity: Total with waste factor included - this is what you should actually order

Drum Requirements: Number of standard 100m drums needed for each cable type

Estimated Cost: Based on approximate UK wholesale prices (2024). Contact distributors for actual quotes.

Cable Waste Factors Explained

Waste factors account for unforeseen circumstances during installation. Here's what to consider when setting your waste percentage:

10% Waste Factor

Best For: Simple, straightforward installations
Examples:
  • New build with clear routes
  • Single room with simple layout
  • Well-planned installations with minimal obstacles

12-15% Waste Factor (Recommended)

Best For: Most typical installations
Accounts For:
  • Route deviations around obstacles
  • Mistakes and rework
  • Extra length for terminations
  • Spare cable for future alterations

20%+ Waste Factor

Best For: Complex or uncertain projects
Examples:
  • Listed buildings with hidden obstacles
  • Retrofits where routing is unclear
  • Multi-story installations with complex routes
  • Projects with design changes expected

Important Note

Running short of cable mid-installation is costly and time-consuming. It's better to have slightly more cable than needed. Most wholesalers won't accept returns of cut cable from drums, so order conservatively.

Installation Planning Tips

Measuring Cable Routes

  • Horizontal runs: Measure actual cable path, not straight line distance
  • Vertical drops: Add ceiling height plus 0.5m for terminations
  • Perimeter routes: Follow walls and add 30% for corners and obstacles
  • Consumer unit runs: Measure from each circuit location to CU via actual cable route

Cable Selection by Circuit Type

  • Lighting: 1.0mm² or 1.5mm² twin & earth (6A/10A MCB)
  • Socket outlets: 2.5mm² twin & earth (16A/20A MCB)
  • Cooker: 6mm² or 10mm² twin & earth (32A/40A MCB)
  • Shower: 6mm² to 10mm² twin & earth (32A-50A MCB)
  • EV charger: 6mm²-10mm² (7kW charger, see EV calculator)

Use the Cable Size Calculator to determine exact cable sizes for your circuits.

Installation Method Considerations

Surface mounting: Quickest installation, cables clipped to surface. Add 10% for clips and routing around features.

Buried in wall: Requires chasing. Cables must run vertically or horizontally only (safe zones). Add 15% for deviations. Buried cables <50mm deep require 30mA RCD protection (BS 7671).

Under floor: Good for ground floor. Add length for joists and routing around obstacles. Consider notch depth regulations.

In conduit: Provides mechanical protection. Add 20% for bends and routes. Check conduit fill capacity (40% max for 3+ cables).

Ordering from Distributors

  • Order cable in standard drum sizes (50m, 100m, etc.)
  • Consider buying one size larger drum if close to the breakpoint
  • Ask about bulk discounts for large projects (3+ drums)
  • Check delivery lead times - cable may need to be ordered in
  • Some distributors offer cut lengths for small jobs (may be more expensive)