Our Cost Methodology
Last reviewed: August 2026
Most cost calculators won’t tell you where their numbers come from. We think that’s backwards — if you’re about to make a decision involving tens of thousands of dollars, you’re entitled to know how the estimate was produced and where it’s likely to be wrong.
This page explains the whole method: what the figures are built from, why cost per square foot falls as buildings get larger, why only part of your project cost changes depending on your state, and what the estimate deliberately leaves out.
Where the kit prices come from
Our pricing is benchmarked against published industry rates for each building size, then positioned below that benchmark to reflect the wholesale pricing we offer. Those same figures appear on every individual size page across this site — the 40×60 page, the 30×40 page, and the full pricing guide all draw on the same numbers.
That consistency is deliberate. The calculator isn’t a separate model that happens to sit alongside our published prices — it is our published pricing, expressed as a formula so it can handle sizes we don’t have a dedicated page for. Enter 40×60 and you’ll get the same range printed on the 40×60 page. Enter 37×53 and you’ll get a figure derived the same way.
Current benchmark rates, kit only:
| Building size | Square feet | Cost per sq ft |
|---|---|---|
| 20×40 | 800 | ~$19.72 |
| 30×40 | 1,200 | ~$19.04 |
| 40×60 | 2,400 | ~$17.86 |
| 40×80 | 3,200 | ~$17.37 |
| 50×100 | 5,000 | ~$16.61 |
| 60×120 | 7,200 | ~$15.99 |
Why cost per square foot falls as buildings get bigger
Notice that a 60×120 costs roughly $4 per square foot less than a 20×40. That isn’t a volume discount — it’s arithmetic, and understanding it will make you a better judge of any quote you receive.
Several costs in a steel building are close to fixed regardless of size. Engineering and code documentation costs roughly the same whether the building is 800 or 8,000 square feet. Delivery is a truck either way. Setup, mobilisation, and permit coordination don’t scale linearly with floor area. Spread those fixed costs across more square feet and the per-foot figure drops.
The decline isn’t linear, though — it flattens out. Going from 800 to 1,600 square feet drops the rate by more than going from 6,400 to 7,200, even though the second jump is the same 800 feet. That’s because you’re halving the fixed-cost-per-foot each time you double the area, not subtracting a constant.
Our model uses a logarithmic curve fitted to the benchmark rates above, which is why it behaves correctly across the whole size range rather than only in the middle. It’s calibrated for buildings between roughly 800 and 20,000 square feet. Outside that range — very small structures, or genuinely industrial-scale spans — the calculator will warn you that the figure is indicative and you should get a real quote.
Kit price vs. installed price
This is the single biggest source of confusion when comparing quotes, and it’s where people get caught out.
A kit price covers the building itself: the primary steel frame, roof and wall panels, one walk door, one drive-in door, engineering stamps sized to your local code, and delivery to your site. What arrives is a complete structure ready for you or a contractor to assemble.
An installed (turnkey) price adds the concrete foundation, professional erection and labour, and permit coordination. The building shows up finished rather than as a kit waiting on a crew.
The gap is substantial — typically $7.50 to $8.75 per square foot on top of the kit, widening slightly on larger buildings — and it’s why a kit quote from one supplier and an installed quote from another aren’t comparable numbers, even though both might be described as a “total.”
Worth knowing: some calculators present an “estimated total project cost” that excludes erection labour and freight. That isn’t a total in any meaningful sense. Ours states plainly which mode you’re looking at and lists what’s in and out of each.
Why only part of your cost changes by state
This is where our method differs most from other tools, and it’s worth explaining properly.
A steel building kit is a manufactured product. It’s fabricated in a plant and shipped to you. Steel is priced on national and global commodity markets, and freight varies far less than most people assume. A 40×60 kit doesn’t cost meaningfully more in Massachusetts than in Mississippi.
Concrete work and erection labour are entirely different. They’re performed by local crews at local wage rates, using concrete from a local plant, under local permitting requirements. These genuinely do vary — substantially — from state to state.
So our calculator holds the kit price constant across all states and adjusts only the site-built portion. The regional factors come from published relative construction cost indices, referenced to a national average of 1.00 and updated annually.
Why this matters more than it sounds
Consider a 40×60 fully installed, and compare our approach against a tool that simply multiplies the whole project by a regional factor:
| State | Our method | Flat multiplier | Difference |
|---|---|---|---|
| Mississippi (0.80) | ~$58,100 | ~$49,600 | $8,600 understated |
| Texas (0.82) | ~$58,500 | ~$50,800 | $7,700 understated |
| National (1.00) | ~$62,000 | ~$62,000 | — |
| New York (1.18) | ~$65,400 | ~$73,100 | $7,700 overstated |
| Alaska (1.25) | ~$66,700 | ~$77,500 | $10,700 overstated |
A flat multiplier understates a low-cost state by nearly nine thousand dollars and overstates a high-cost state by more than ten. In both directions, that’s a number you’d plan around and then be badly surprised by.
The error comes from applying a labour-cost adjustment to steel, which doesn’t behave like labour at all.
What the range means
Every figure is shown as a range of roughly ±8% rather than a single number. That band accounts for specification differences between suppliers, gauge and finish variation, and normal market movement in steel pricing.
We show a range because a single number would imply a precision that doesn’t exist at the estimating stage. Any calculator returning one exact figure for a custom-engineered structure is telling you something it can’t actually know.
The range is not a substitute for the site-specific factors below. Those sit outside the ±8% entirely.
What the estimate excludes
Deliberately left out, because they’re impossible to estimate without knowing your site:
- Site conditions — clearing, grading, drainage, or difficult access
- Wind and snow load engineering beyond standard code for your area. Coastal and heavy-snow regions can require heavier gauge and additional bracing.
- Permits and inspection fees, which vary by jurisdiction more than by state
- Interior finish-out — walls, ceilings, flooring
- Electrical, plumbing, and HVAC
- Custom colours, additional windows, or non-standard door configurations
Insulation and additional door figures in the calculator are industry-typical allowances, not our published rates. They’re there to give you a realistic project total, and we flag them as estimates rather than presenting them with the same confidence as our kit pricing.
Known limitations
Being straightforward about where this is weakest:
Extreme sizes. The model is calibrated between roughly 800 and 20,000 square feet. Below that, fixed costs dominate in ways a smooth curve doesn’t capture well. Above it, projects get quoted individually.
Very wide spans. Past about 100 feet of clear span, engineering requirements change enough that per-square-foot modelling becomes unreliable. The calculator warns you at this point.
Regional indices are broad. They’re state-level averages. Construction costs vary substantially within states — a metro area and a rural county in the same state can differ more than two neighbouring states do.
Steel prices move. Our benchmark rates are reviewed periodically, but steel is a commodity and can move faster than any published guide updates. The date at the top of this page tells you when these figures were last reviewed.
It’s an estimate, not a quote. No calculator can account for your specific site, code requirements, and configuration. The purpose here is to get you to a realistic budget range before you talk to anyone — not to replace an actual quote.
How often this is updated
Benchmark rates are reviewed when steel pricing moves materially or at least annually. Regional cost factors are refreshed annually as new index data publishes. The “last reviewed” date at the top of this page is updated whenever either changes.
Get a real number
The calculator will get you to a realistic budget range in about thirty seconds. When you’re ready for a figure you can actually build a plan around — priced for your exact site, foundation, and finish level — that takes a few minutes.
Get your free, no-obligation quote →
14,068 kits sold · 50-year structural warranties · Wholesale pricing
Get Your Free Quote
Answer a few quick questions and we’ll match you with suppliers who quote your exact size and location. Takes about two minutes.
14,068 kits sold • 50-year structural warranty • Free, no obligation
