Electrical Calculator — Outlets, Cable, Boxes & Circuits
Plan a first fix: the socket outlets, switches and light points on a run, the cable they need, and the boxes, breakers and conduit that go with them. Quantities for planning only — the rules that govern an installation are local, and this page makes no claim about them.
Materials
Price estimate
Quantities for planning only. Outlet spacing, cable sizing, circuit loading and who is allowed to do the work are set by local rules that differ by country — check them, and have the installation done by a qualified electrician.
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How the electrical calculator works
- 1Points: type a count, or space them along the run — run length ÷ spacing, plus one
- 2Circuits = points ÷ points per circuit, rounded up, with one breaker each
- 3Cable is built from four lengths you can check: a home run to the board per circuit, one pass along the run, a drop to each wall point, and the tail left at every box
- 4Slack goes on as a percentage, so the total can be compared with how cable is sold — a 50 m reel, or 250 ft
- 5One back box per point; conduit, where used, follows the cable length
Worked example
One room: 18 m of wall at 2.4 m high — 59 × 8 ft — with 6 socket outlets, 2 switches, 2 light points, and 10 m (33 ft) back to the board.
10 points on 1 circuit: 10 back boxes, 1 breaker, and 45.5 m of cable — 149 ft, so one 50 m reel with nothing cut from a second.
Frequently asked questions
Does this follow the wiring rules where I live?
No, and it does not try to. Outlet spacing, cable sizing, circuit loading and who is allowed to do the work are set locally and differ by country. The spacing field is your own planning rule, not a requirement — have the installation designed and carried out by a qualified electrician.
Why is the cable figure longer than the wall?
Because cable does not run in a straight line. The length is the home run to the board, the pass along the wall, a drop down to each wall point and the tail at every box, with slack on top. 10% is a common allowance; raise it where the route bends or crosses a ceiling.
Does it work in feet and inches, and in my currency?
Yes. Every length follows the EU/US toggle in the header and every price follows the currency setting, so the same run reads as 18 m or 59 ft with nothing re-typed. No market is baked in.
Plan the whole job
One calculation is one line of a job. With the floor planner you draw the room once and every calculator on the site fills itself from those measurements, with the openings taken off. The project manager then holds every room and trade against one budget, and tracks what things actually cost as the invoices arrive.