Wire cut-length calculator
From the length along the branches to the length you cut: every term added, and why.
No account. Nothing is stored. · Last updated
In short
Cut length = path length + an allowance at each end + service loops, then slack (a percentage), a fixed addition and, for twisted wires, the take-up of the twist — rounded the way your shop rounds. The path is the sum of the branch lengths the wire runs through on the drawing. The allowance is the distance from the branch's dimension point to the wire's termination, strip length included.
Worked example
A 1,000 mm path, 20 mm allowance at each connector, a 50 mm service loop at one end, 2 % slack, rounded up to 5 mm: 1,090 mm before slack, 1,115 mm to cut.
How it works
- Path
- The sum of the branch (segment) lengths between the wire's two ends. On a drawing dimensioned between branch points, add the branches the wire passes through.
- Allowance at each end
- From the dimension point of the branch to the end of the wire inside the termination, strip length included. It depends on the connector: deep housings, back-shells and sealed connectors need more.
- Service loop
- Extra wire left at an end so the connector can be re-terminated or moved in service.
- Slack
- A percentage for routing around the pegs of the formboard and for bundle curvature.
- Fixed addition
- A constant some shops add to every wire (or a negative one, to trim).
- Twist take-up
- A twisted pair is shorter than its wires: the take-up is a percentage of the length, with a minimum.
- Rounding
- Up to a step (never too short), to the nearest step, or none.
These are Zorowire's length rules (the same order of operations as the Workspace). The allowance, loop, slack and twist values are yours to set; nothing here is a standard.
Questions
- Why round up instead of to the nearest step?
- Rounding up never cuts a wire too short; a few millimetres of extra copper cost less than a scrapped wire. Shops with a machine that cuts to the millimetre often round to none.
- How do I find the twist take-up?
- Twist a metre of your pair at your lay length and measure how much shorter it gets. That percentage, with a minimum for short pairs, is the take-up.
- Is the slack applied to the loops too?
- Yes. The slack percentage applies to the path, the allowances and the loops together; the fixed addition comes after it.
- What about a cable with several cores?
- Cut the cable to the longest of its cores. In the Workspace this is automatic.
Sources
Zorowire's own method, the same code as the Workspace; no outside data is used.
Last updated
Do it for real harnesses in the Workspace
Enter a harness once — connectors, wires, branch lengths — and Zorowire keeps the quote, the cut list, the 1:1 formboard, labels and the BOM in step. The Free plan needs no card.