Why does cost per unit fall as the run grows?

Setup, fixture and imbalance dollars are fixed, so a longer run spreads them over more units. The variable station cost per unit stays the same, so only the fixed share per unit falls.

What is the variable station cost per unit?

The cost each unit adds as it passes through the stations, such as consumables, power and operator time tied to pace. It excludes changeover, fixtures and imbalance, which appear as fixed adders.

Should I use the total or the per-unit row for a quote?

The per-unit row, because quotes are priced per unit. The total is the cash the run spends, useful for the shop budget; the per-unit row is the number to compare with the target.

Why does a short run miss the target?

The fixed adders spread over fewer units, so cost per unit rises. At 110 units the default run carries about 5.82 dollars per unit of fixed adders, against roughly 1.16 dollars at 550 units.

Furniture, Fixtures & Interior Products calculator

Assembly Station Balance Calculator

Add variable station cost, setup and fixtures, and imbalance overhead, then spread the total across the units in the run. The page compares cost per unit with your target.

What this calculator does

Total assembly station cost per run and cost per unit against a target, with setup spread over the run.

Formula used

Total assembly station cost = units × variable station cost per unit + setup and fixture cost + labor imbalance and overhead
Cost per assembled unit = total station cost ÷ units in the run
Variable station cost = units × variable station cost per unit
Fixed adders = setup and fixture cost + labor imbalance and overhead
Cost vs target per unit = target cost per unit − cost per assembled unit

Inputs explained

Assembled Units in the Run: Units started through the stations in this run.
Variable Station Cost per Unit: Cost each unit adds at the stations before setup.
Setup and Fixture Cost: Changeover, fixture and first-piece cost for the run.
Labor Imbalance and Overhead: Time balancing and idle share applied to this run.
Target Cost per Unit: Unit cost target from the quote or cost sheet.

How to use the result

Best suited to choosing a run length for a cabinet box, comparing per-unit cost across run sizes, checking a quote against a unit target.
It spreads setup evenly; a partly completed run still carries the full setup here. Rework or extra stations added after imbalance correction sit outside the model.

Current U.S. benchmarks

The producer price index for lumber stands at 286.633 (BLS, Aug 2026), up 7.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 14,378 furniture and related products establishments employing about 355,594 workers (Census County Business Patterns, 2023).

Common questions

Why does cost per unit fall as the run grows? Setup, fixture and imbalance dollars are fixed, so a longer run spreads them over more units. The variable station cost per unit stays the same, so only the fixed share per unit falls.
What is the variable station cost per unit? The cost each unit adds as it passes through the stations, such as consumables, power and operator time tied to pace. It excludes changeover, fixtures and imbalance, which appear as fixed adders.
Should I use the total or the per-unit row for a quote? The per-unit row, because quotes are priced per unit. The total is the cash the run spends, useful for the shop budget; the per-unit row is the number to compare with the target.
Why does a short run miss the target? The fixed adders spread over fewer units, so cost per unit rises. At 110 units the default run carries about 5.82 dollars per unit of fixed adders, against roughly 1.16 dollars at 550 units.

Last reviewed 2026-10-01.