Hose Calculations

How to Calculate Hose Assembly Yield, Crimp Force, and Burst Margin

The four formulas that govern hose assembly production, each worked with real units and inputs so you can run them on your own jobs.

Start with cut length yield, because it sets your material draw. A finished 3/8 inch hydraulic assembly with two crimped ends needs cut hose equal to overall length minus twice the fitting insertion depth, plus a saw kerf allowance. If the callout is 24 inches overall, insertion is 0.94 inch per end, and kerf is 0.06 inch, cut length equals 24 minus 1.88 plus 0.06, or 22.18 inches. From a 328 foot (3936 inch) coil you get floor(3936 / 22.18) equals 177 pieces. The Hose Cut Length Yield calculator handles kerf and insertion loss so you stop rounding by feel.

Coil usage rarely divides cleanly, so quantify the remnant. With 177 pieces at 22.18 inches you consume 3925.86 inches and leave 10.14 inches, too short for a 22 inch piece, so it becomes drop. That remnant is 0.26 percent of the coil here, but on short assemblies cut from long stock the drop can climb past 4 percent. Track it as inches lost per coil, not a vague percentage, because a 0.06 inch kerf across 177 cuts alone eats 10.6 inches, nearly a full extra piece of usable hose per coil.

Crimp force is the number that makes or breaks a joint. Required force scales with the projected contact area under the dies and the target compression stress. Approximate it as force equals contact area times unit crimp pressure, where area is die length times crimp diameter times pi, adjusted for the number of segments. For a 1 inch die length on a 0.62 inch crimp diameter at 55,000 psi effective pressure, projected area near 1.95 square inches yields roughly 107,000 lbf. The Crimp Force Window calculator returns the low and high bounds so your press setting lands inside the die spec, not just above the minimum.

The crimp window matters more than the single target. A fitting rated for a 0.610 to 0.618 inch crimp diameter has a window of only 0.008 inch. Undercrimp by 0.004 inch and pull-off strength can drop 20 to 30 percent; overcrimp by the same amount and you cut hose reinforcement wires. Convert the diameter window into a force window using the same area relationship, then verify your press repeatability. If the crimper holds plus or minus 0.003 inch, an 0.008 inch window leaves almost no margin and you should tighten die maintenance intervals.

Burst pressure margin ties the assembly back to its rating. Working pressure equals burst pressure divided by the design safety factor, which is 4:1 for most hydraulic hose per SAE J517. So a hose with 12,000 psi minimum burst carries a 3,000 psi working rating. To check margin on a real assembly, divide measured or rated burst by the system working pressure. A 5,800 psi system on that 12,000 psi hose gives a 2.07:1 actual margin, below the 4:1 design intent, a red flag. The Burst Pressure Margin calculator flags any combination that falls under target.

Proof pressure sits between working and burst, typically 2 times working pressure per SAE, held without leakage or permanent deformation. On the 3,000 psi rated hose, proof is 6,000 psi. When you validate assemblies, do not confuse proof with a leak test. Proof confirms structural integrity at double the rating; a leak test runs near working pressure to catch fitting seal defects. Mixing the two either overstresses good parts or passes leakers. Keep the burst safety factor, proof multiplier, and leak test pressure as three distinct inputs in your traveler.

Leak test throughput drives how many assemblies clear the bench per hour. Cycle time is fill time plus stabilization dwell plus hold plus vent. If fill is 8 seconds, stabilization 5 seconds, hold 15 seconds, and vent 4 seconds, cycle is 32 seconds, so a single station clears 3600 / 32 equals 112 parts per hour at 100 percent uptime. Apply a realistic 85 percent utilization and you get 95 parts per hour. The Leak Test Throughput calculator lets you tune dwell and hold to find where longer holds stop catching more leaks.

Two supporting numbers round out a job sheet. Coil capacity tells you how many finished assemblies a spool holds for shipping or staging: divide usable spool length by assembly length plus a bend allowance, which the Coil/Spool Capacity calculator computes from core diameter and flange width. Fitting assembly time, the manual insert and orient step before crimping, typically runs 25 to 60 seconds per end depending on fitting style and thread type; the Fitting Assembly Time calculator converts that into pieces per labor hour so your cut, crimp, and test rates all reconcile against the same clock.

Published 2026-07-01.