Ductwork Takeoff and Bids
How duct is measured from the plans and how sheet metal subs price it.
Quick Answer
A ductwork takeoff measures each duct run by size and length, counts the fittings, and converts them to sheet metal surface area or weight. Duct subs commonly price by the pound or square foot of fabricated duct, with insulation, dampers, hangers and diffusers listed separately. The bid scope decides what is included.
The Full Picture
Ductwork is measured from the mechanical plans and sections. For each run the estimator records the shape, the size (rectangular width and height, or round diameter), the length, the pressure class or construction type, and the material. Fittings such as elbows, transitions, tees and takeoffs are counted individually or measured as equivalent lengths, because a fitting takes more labor and metal than the same length of straight duct. Duct is built to standards, and project specifications commonly require construction per the latest SMACNA duct standards with the specification section for ducts and casings in Division 23 (23 31 00).
Sheet metal is priced on surface area. Perimeter times length gives square feet, and square feet times the weight per square foot of the gauge gives pounds. The gauge and reinforcement depend on size and pressure. One spec requires medium-pressure ductwork to be built to table 1.8 of the SMACNA HVAC Duct Construction Standards, and the same document defines the pressure ranges, so the pressure class on the drawings changes both the metal and the price. Gauge weights should come from the manufacturer or SMACNA tables the sub uses, not from memory.
Duct subs commonly price one of two ways, by weight of fabricated duct with a labor rate for installation, or by unit prices per pound or per square foot. Which one is used varies by sub and region. What matters to the general contractor is the scope sheet. Typical separate items are duct insulation or lining, access doors, volume and fire dampers, turning vanes, flexible duct, hangers and supports, sealing, pressure testing, diffusers and grilles, and test and balance. Specs may add requirements that raise cost, such as pressure testing for ductwork at a pressure class of 2 inches and greater or sealing every seam and joint, and these may not be obvious from the drawings alone.
Bid leveling matters because the same duct can be quoted on different bases. One bidder may include fittings in the pound rate and another may price them separately. One may carry insulation and another may not. Others price the duct but exclude diffusers, flexible runs or the roof curbs and sleeves. An estimator who levels bids puts each one on the same inclusion list, checks the duct quantity against an independent takeoff, and flags large gaps in weight or length before the numbers are accepted.
Real Examples
Common Misconceptions
People assume: A duct takeoff is just total linear feet of duct.
Actually: Length alone misses the cost. Size, gauge, pressure class, fittings and reinforcement change the metal and the labor, so duct is converted to area or weight. Two runs of equal length can differ a lot in price.
People assume: The duct bid covers everything in the air system.
Actually: Insulation, dampers, diffusers, grilles, flexible duct, balancing and controls are often separate lines or separate trades. Specs can also add sealing of the entire duct system to the sub's scope. Check the inclusion list before comparing totals.
Does MeltPlan Solve This?
Yes — direct fitMeasuring duct by size and length and counting fittings from the mechanical plans is exactly the work of a ductwork takeoff. MeltPlan's takeoff service has AI pull quantities from plans and US-based experienced estimators review and adjust them, so the result is a verified, ready-to-use takeoff. It works from PDF plans, not BIM models. Gauge selection, the sub's pricing and bid leveling stay with your estimating team.
Get ductwork measured from your mechanical plans →Frequently Asked Questions
How is ductwork measured in a takeoff?
By size and length for each run, with fittings counted or converted to equivalent length. The estimator then converts to square feet of sheet metal or pounds, depending on how the sub prices. Flexible duct is normally measured in linear feet.
How do duct subs price ductwork?
Commonly by weight or area of fabricated duct plus labor, or as a unit price per pound or per square foot. It varies by sub and region, so ask each bidder for the basis and the inclusions.
What is usually priced separately from the duct?
Insulation or lining, access doors, dampers, turning vanes, flex duct, hangers, diffusers and grilles, test and balance, and sometimes pressure testing. The scope letter should say which are in or out.
Which standard governs duct construction?
Project specs usually reference SMACNA's HVAC Duct Construction Standards. For example, one university standard requires ductwork to be built per the latest SMACNA guidelines. The project's own specification governs.
How do you convert duct size to weight?
Perimeter times length gives surface area in square feet. Multiply by the weight per square foot of the specified gauge to get pounds, then add fittings and waste. Use weights from the sub's or SMACNA's tables.