How do you calculate coating cost per square?

Multiply squares coated by the paint and primer cost per square, then by transfer efficiency, then add the changeover cost, and divide by squares. With 800 squares at $6.20, 90% transfer efficiency and $95 changeover, the total is $4,559, or $5.70 per square.

Why is my per-square cost higher than the paint price?

Transfer efficiency and changeover. At $6.20 raw paint and 90% efficiency the applied variable cost is $4,464 across 800 squares, and the $95 purge adds $0.12 per square, landing at $5.70 instead of $6.20.

What is a good transfer efficiency for coil and spray coating?

Coil coating and roll application routinely hit 95-99%, while air-spray on profiled siding can drop to 50-70%. The 90% default reflects an efficient electrostatic or curtain-coat line; lower efficiency directly inflates cost per square.

How much does color changeover add per square?

In this example $95 of purge and flush spread over 800 squares adds about $0.12 per square. On short runs of 100-200 squares the same $95 can add $0.50 or more, which is why short color runs are expensive.

Coil coating vs spray coating cost per square?

Coil coating has higher transfer efficiency and lower waste, so its cost per square is usually lower on long runs; spray wins only on small-batch or three-dimensional parts where coil line setup is not justified.

Does this include cure oven or labor cost?

No. It isolates paint, primer, transfer loss, and changeover. Add oven energy, line labor, and depreciation separately if you need a fully loaded applied-finish cost per square.

Roofing, Siding & Exterior Building Products calculator

Coating cost per square Calculator

Coating Cost per Square tells a coil-coating or spray line what it actually spends to finish 100 square feet (one "square") of roofing, siding, or trim once paint waste and color-change losses are counted. Process engineers and estimators at metal roofing, fiber-cement, and vinyl siding plants use it to price jobs and to compare coating chemistries. Because transfer efficiency and purge cost are baked in, it exposes the real applied cost that a raw $/square paint quote hides. On a shop floor that runs dozens of colors a week, the changeover adder is often where the margin quietly leaks.

What this calculator does

Estimates coating cost across a roofing or siding run from squares coated, paint and primer cost per square, coating transfer efficiency, and a flat color-changeover charge.
A coil-coating or panel-finishing planner uses it to price the paint and primer needed to finish a run of metal roofing or siding in a given color.
It computes the total and per-square coating cost for a production run by applying transfer efficiency to your paint spend and adding fixed changeover cost.

Formula used

Total coating cost = squares coated x coating cost per square x transfer efficiency + changeover
Coating cost per square = total / squares coated

Inputs explained

Squares coated in the run:
Paint & primer cost per square:
Transfer efficiency to product:
Line purge & color changeover:

How to use the result

Use it when quoting a coated-product run, comparing two coatings or applicators, or investigating why applied paint cost is higher than the drum price implies.
It assumes a single blended paint/primer rate and one changeover event per run; multiple color changes or dual-coat systems need the fixed adder and per-square rate adjusted accordingly.

Current U.S. benchmarks

U.S. housing starts run at 1,177k per year (Census, May 2026), down 8.7% from a year earlier, the demand driver for building products.

Common questions

How do you calculate coating cost per square? Multiply squares coated by the paint and primer cost per square, then by transfer efficiency, then add the changeover cost, and divide by squares. With 800 squares at $6.20, 90% transfer efficiency and $95 changeover, the total is $4,559, or $5.70 per square.
Why is my per-square cost higher than the paint price? Transfer efficiency and changeover. At $6.20 raw paint and 90% efficiency the applied variable cost is $4,464 across 800 squares, and the $95 purge adds $0.12 per square, landing at $5.70 instead of $6.20.
What is a good transfer efficiency for coil and spray coating? Coil coating and roll application routinely hit 95-99%, while air-spray on profiled siding can drop to 50-70%. The 90% default reflects an efficient electrostatic or curtain-coat line; lower efficiency directly inflates cost per square.
How much does color changeover add per square? In this example $95 of purge and flush spread over 800 squares adds about $0.12 per square. On short runs of 100-200 squares the same $95 can add $0.50 or more, which is why short color runs are expensive.
Coil coating vs spray coating cost per square? Coil coating has higher transfer efficiency and lower waste, so its cost per square is usually lower on long runs; spray wins only on small-batch or three-dimensional parts where coil line setup is not justified.

Last reviewed 2026-05-12.