How to Price Ductwork Jobs: A Contractor's Cost Build

By SubcontractorHub Editorial Team·Published August 2026

Ductwork is the part of an HVAC job most likely to be underpriced, and the reason is structural rather than careless. Equipment has a list price you can look up. Duct has a quantity you have to derive, a labour content that depends on where a human body can physically fit, and a long tail of small accessories that individually look trivial and collectively decide whether the job made money.

This is a cost build rather than a price list. Work through the five components below with your own numbers and you will get a defensible price for a residential replacement, a partial repair, or a commercial package — and you will know which line to point at when a customer asks why a competitor came in lower.

Start With the Load, Not the Tape Measure

Before quantity comes sizing. Manual J establishes what the building actually needs and Manual D sizes the trunk and branches to deliver it. Skipping this and matching the old system is the most common way a duct quote goes wrong in both directions: undersize and you inherit comfort complaints and callbacks you pay for, oversize and you have quietly bought material and labour the job never needed.

There is a commercial argument for it too. A load calculation is the strongest answer to "the other guy quoted less" — a competitor who sized off the existing system has not priced the same job, and being able to show why is worth more than discounting. Run the numbers with the Manual J load calculator and the duct size calculator, and see the load calculation guide for the method.

The Five Components of a Ductwork Price

1. Material, by type and gauge

Duct material is not one line. Rectangular sheet metal trunk, round or spiral, flexible branch runs, and rigid fiberglass ductboard all carry different unit costs and different labour content, and gauge matters — heavier gauge costs more per square foot of metal and takes longer to fabricate and hang. Most residential jobs are correctly quoted as a hybrid: sheet metal trunk with flex branches. Say so in the proposal, because otherwise the customer compares your number to an all-flex bid without knowing the difference.

2. Fabrication, separately from installation

If you run a sheet metal shop, shop hours and field hours are different costs and should be estimated separately. Fittings are where this bites: transitions, offsets, boots, and takeoffs carry far more fabrication time per piece than straight duct, so a system with many directional changes costs materially more than its linear footage suggests. If you buy fittings rather than fabricating, that becomes a material line instead — but it should still be counted per fitting, not absorbed into a per-foot rate.

3. Field labour at your burdened crew rate

Duct work is labour-heavy, which makes labour burden the single highest-leverage number in the estimate. Payroll taxes, workers' compensation, general liability, vehicle, tools, and non-billable time typically add 25% to 50% on top of base wage. Estimating at wage instead of burdened cost understates a duct job by more than any material assumption will. Work out your real number with the labor burden calculator.

4. The access multiplier

This is the line that separates estimators who have done the work from those who have not. The identical duct run costs radically different amounts depending on where it goes, and the multiplier applies to labour hours rather than to material:

Deliberately no fixed multipliers here — yours should come from your own completed-job hours, because they vary by crew and by region. The important discipline is that the multiplier is an explicit line in the estimate rather than an instinct applied at the end.

5. The accessories nobody counts

Individually small, collectively the margin: boots and registers, balancing dampers, takeoffs and collars, hangers and strapping, mastic and foil tape, insulation to the required R-value, zone dampers if applicable, plus permit and inspection where required. Add commissioning — static pressure readings, airflow balancing, and a duct leakage test where code requires one. If your estimate does not have a line for testing, you are giving it away.

Worked Example: Whole-House Replacement

Structure matters more than the specific figures — substitute your own rates. A 2,000 square foot single-storey home, sheet metal trunk with flex branches, ten supply drops and two returns, attic distribution:

That last line is where a surprising number of contractors lose money. Adding 30% to cost does not produce a 30% margin — it produces about 23%. The distinction compounds on labour-heavy work like duct replacement. The markup vs margin calculator shows the gap, and the job profit calculator checks the finished number.

For a typical home this build usually lands somewhere between $6,000 and $16,000 installed, but treat that as a sanity check on your own arithmetic rather than a target. If your build comes out well below it, you have probably missed access or accessories.

Repairs and Partial Work Need a Minimum

Sealing a few joints, replacing a collapsed flex run, or adding a single drop carries the same fixed costs as a large job — the truck roll, the diagnostic time, the trip to the supply house — spread over a fraction of the revenue. Small duct work needs a minimum charge that recovers those, and it needs to be quoted from a flat-rate book rather than computed fresh at the kitchen table. See the flat rate pricing guide and the service call cost calculator.

Commercial Ductwork Is a Different Estimate Entirely

On commercial and mechanical work the method changes on both ends. Quantity comes off drawings and a specification rather than a walkthrough, sheet metal is frequently estimated by the pound with gauge and construction dictated by SMACNA standards and the spec, and seismic bracing, fire dampers, welded or specialty duct, and insulation requirements are prescribed rather than chosen.

The billing changes too, and this is the part residential contractors moving into commercial work underestimate. You are not invoicing on completion — you are billing monthly against an approved schedule of values with 5–10% retainage withheld, and change-order administration will decide much of the final margin. Prevailing wage and certified payroll apply on most public work. See mechanical contractor software, the schedule of values calculator, and the progress billing guide.

Commercial duct is estimated from drawings and a spec — gauge, bracing, and dampers are prescribed rather than chosen, and the work is billed in draws rather than invoiced at the end.

Where Duct Jobs Actually Lose Money

Almost never material prices. In practice it is two things. The first is access underestimated from a walkthrough — an attic that looked workable in April is a different job in July, and a chase that looked open needs drywall opened and patched. The second is scope discovered mid-job and performed without a documented change order: asbestos-wrapped duct, undersized returns nobody measured, a structural obstruction. The crew is on site, the customer is standing there, and saying yes is easier than pricing it.

That second failure is procedural, not technical, and it is fixable. Photograph the condition, price the change, get an approval on the spot, and only then proceed. Reps who build proposals in EasyQuote can issue a priced change and capture a signature from the driveway, which is the difference between a paid extra and a write-off. Presenting financing alongside the revised total is also what keeps a larger scope from being cut back to fit a budget.

Frequently Asked Questions

Related Guides

• How to Price HVAC Jobs
• HVAC Load Calculation Guide (Manual J)
• HVAC Flat Rate Pricing Guide
• HVAC Duct Size Calculator
• Manual J Load Calculator
• Labor Burden Calculator
• Markup vs Margin Calculator
• Best HVAC Estimating Software in 2026
• Mechanical Contractor Software
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