Harness Formulas

How to Calculate Wire Harness Build Metrics: Cut Length, Crimp Load, and Test Time

The core wire harness math, worked end to end: cut length with strip and service allowances, crimp labor load, and continuity test time.

Cut length is the first number that has to be right, because every downstream operation inherits its error. Start with the routed path length from the 3D model or formboard, then add allowances: cut length equals routed length plus two strip lengths plus service loop plus tolerance slack. A wire routed 480 mm with a 7 mm strip each end and a 25 mm service loop needs 480 plus 14 plus 25, so 519 mm before cut tolerance. Add roughly 1 percent slack for cut-and-strip machine repeatability, giving about 524 mm. The Wire Cut Length calculator handles the allowance stack so you are not adding strip length twice or forgetting the loop.

Crimp labor load drives most of the touch time in a harness, so count crimps before anything else. Total crimps equals the sum over each wire of its terminated ends, typically 2 per discrete wire, minus any splice-shared ends. A 40-circuit harness with 4 splices carrying 3 wires each has roughly 80 wire ends minus the splice consolidation, landing near 74 crimp cycles. At a benched rate of 4.5 seconds per applicator cycle plus 6 seconds handling per crimp, that is 10.5 seconds each, so 74 crimps take about 13 minutes. Feed these counts into the Crimp Labor Load calculator to convert cycle time into minutes per assembly.

Continuity and hipot testing scales with net count, not wire count, and people confuse the two constantly. Test points equal the number of connector cavities populated, and the test matrix checks every net for continuity plus every net pair for isolation. A 60-cavity harness with 45 distinct nets needs 45 continuity checks; a bed-of-nails tester runs these in parallel in roughly 8 to 15 seconds regardless of count, but manual point-to-point runs near 6 seconds per net, so 45 nets take about 4.5 minutes by hand. The Harness Test Time and Continuity Test Workload calculators separate fixtured parallel testing from sequential manual probing so your quote matches your actual method.

Routing and dress labor is the hidden line item, and it correlates with breakout count and bundle length rather than circuit count. A useful estimate is routing time equals base handling plus breakouts times per-branch dress time plus bundle length times a lay-in rate. For a harness with 6 breakouts and 2.1 meters of trunk, using 45 seconds per breakout and 20 seconds per meter, routing runs 6 times 45 plus 2.1 times 20, so 270 plus 42, about 5.2 minutes before tape and tie. The Routing Labor calculator lets you tune the per-breakout and per-meter rates to your own formboard time studies.

Wire consumption and scrap close the loop between the cut plan and material purchasing. Gross wire per assembly equals the sum of all cut lengths divided by 1 minus the scrap fraction. If total finished cut length is 42 meters and your cut-and-strip scrap runs 4 percent from lead ends and setup slugs, gross consumption is 42 divided by 0.96, about 43.75 meters. That 1.75 meter delta, multiplied across a 5,000-unit run, is 8,750 meters of wire you must buy but never ship. The Cable Scrap Cost calculator ties this scrap fraction to spend so the number is visible instead of buried in yield.

Units trip up more calculations than math does, so lock them early. Keep all lengths in millimeters through the cut plan and convert to meters only at consumption, keep all labor in seconds through the count and convert to minutes only at the assembly total, and keep wire gauge as AWG but pull mass from a gram-per-meter table, since 20 AWG is about 8.5 g/m and 16 AWG about 21 g/m. Mixing meters and millimeters in a service loop is the classic error that inflates cut length by a factor of ten and passes silent review until the wire will not seat.

To assemble a full per-unit build time, sum the operation minutes: crimp load, routing, testing, plus lead prep and final assembly. Using the numbers above, a mid-complexity 40-to-60 circuit harness lands near 13 minutes crimp, 5 minutes routing, 5 minutes test, and roughly 7 minutes lead prep and dress, totaling about 30 minutes of direct labor. The Cable Assembly Labor calculator rolls these operation-level estimates into one standard time you can compare against your measured cycle, and any gap over 15 percent usually means a missed operation rather than a slow operator.

Published 2026-07-01.