Electrical cable calculator
For planning a rewire, the cable length can be estimated from the number of points and their average distance from the consumer unit, plus a reserve for drops and connections in boxes.
Your measurements
Result
- Cable needed (incl. 15% reserve)
- 69.0 m
An average estimate; real routes through walls and ceilings are longer than straight lines. The work must be done and tested by a qualified electrician.
How the calculation works
- Base length = number of electrical points × average distance from the consumer unit to a point.
- Length to order = base length + 15% for drops, rises and connections.
Worked example
For 10 points at an average distance of 6 m from the consumer unit: 10 × 6 = 60 m, plus 15%, so about 69 m of cable.
What the calculator assumes
- The average distance is measured along the real route, on walls and through ceilings, not in a straight line.
When to adjust the result
- The calculation doesn't distinguish circuits: in practice several sockets on one circuit are chained, which shortens the route.
- Cable size differs by circuit (commonly 1.5 mm² for lighting, 2.5 mm² for sockets, larger for hobs, ovens and water heaters) and is set by local wiring rules.
- Conduit, boxes and earthing are not included. Electrical work must be designed, carried out and tested by a qualified electrician under local rules.
Measuring cable runs realistically
Cable runs are always longer than the straight-line distance: cables go up and down walls, follow safe zones and turn at corners. Measure along the actual route, add the height from the floor or ceiling to each outlet and allow 20–30 cm at each box for connections, plus 10–15% overall.
Cable size depends on the circuit's protective device, its length and how it is installed — buried in insulation it carries less current. Run cables vertically or horizontally from outlets in the zones your local wiring rules define, so nobody drills into them later.
Frequently asked questions
How much cable to rewire a house?
Count the points, estimate their average route length to the consumer unit and add 15% — then let the electrician confirm per circuit.
What size cable for sockets?
In many European countries 2.5 mm² for socket circuits and 1.5 mm² for lighting, but local regulations decide.
What cable size for sockets and lighting?
Sizes depend on local wiring rules and protection; lighting circuits typically use smaller cable than socket or cooker circuits. Have the design checked by an electrician.
Why add extra cable at each box?
Connections need loose ends to strip and terminate, and a short loop allows a fitting to be replaced later without re-pulling the cable.