Thermoforming & Vacuum Formed Products calculator

Stack Height Calculator

Stack Height turns a run's total part count and runtime into an effective per-hour throughput, discounted by how efficiently the line actually ran. Production supervisors and planners use it to convert last shift's output into a rate they can schedule and quote against. It matters because a raw parts-per-hour figure flatters the line — it ignores the minor stops, slow cycles, and speed losses that separate the count you'd hope for from the count you'll get. Applying an efficiency factor gives you a defensible, repeatable throughput number for the vacuum forming and stacking operation rather than a best-case guess.

What this calculator does

  • Stack Height turns a run's total part count and runtime into an effective per-hour throughput, discounted by how efficiently the line actually ran.
  • Use it when stack height in thermoforming and vacuum formed products is being committed and you need a throughput number you can defend.
  • It divides completed output by runtime to get a raw throughput rate, then multiplies by line efficiency to give effective throughput per hour.

Formula used

  • Raw stack height = completed output ÷ runtime
  • Effective stack height = raw throughput × efficiency

Inputs explained

  • Parts formed over the run:
  • Line runtime:
  • Line efficiency:

How to use the result

  • Use it when converting a completed run into a plannable hourly rate, comparing shifts, or feeding a realistic rate into a capacity or scheduling model.
  • It bundles all losses into one efficiency figure, so it won't tell you whether the shortfall came from micro-stops, speed loss, or downstream stacking jams — use it for rate-setting, not root-cause diagnosis.

Current U.S. benchmarks

  • The producer price index for plastic resins and materials stands at 319.371 (BLS, May 2026), up 19.5% from a year earlier. Quotes priced off last quarter's material cost miss this move.
  • The U.S. has 9,635 plastics product manufacturing establishments employing about 677,302 workers (Census County Business Patterns, 2023).

Common questions

  • How do you calculate stack height throughput? Divide parts produced by runtime for the raw rate, then multiply by efficiency. With 1,200 parts over 8 hours at 90% efficiency, raw throughput is 150 units/hr and effective throughput is 135 units/hr.
  • What is the difference between raw and effective throughput? Raw throughput (150/hr) is simply output divided by runtime — the rate the run appeared to hit. Effective throughput (135/hr) discounts it by efficiency to give the sustainable rate you should schedule against.
  • What is a good line efficiency for thermoforming? Well-run continuous formers with automated stacking often sit around 85-92% efficiency; the 90% used here is a solid target. Below about 80%, micro-stops and stacking jams are usually eating the difference.
  • Why not just quote the raw rate? Because raw rate is a peak snapshot that ignores the small losses every real shift accumulates. Quoting 150/hr when the line sustains 135/hr overcommits capacity by roughly 10% — enough to blow a delivery date over a long order.
  • How do I raise effective throughput? Because efficiency multiplies the raw rate directly, closing micro-stops and stacking jams is the fastest lever — moving from 90% to 95% here would lift effective throughput from 135 to about 142/hr with no faster cycling.

Last reviewed 2026-05-12.