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Calculation Machine

Duct Surface Area Calculator

Total surface area of a duct run.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Perimeter
31.4 in
Total surface area
65.4 sq ft
Insulation needed (with 10% waste)
72 sq ft

Quick answer

Duct surface area equals the perimeter of the cross-section multiplied by the duct's length.

The formula

Surface area = perimeter x length

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Duct shapeRound
  • Diameter or width10 in
  • Height (rectangular only)8 in
  • Duct length25 ft

Result

  • Perimeter31.4 in
  • Total surface area65.4 sq ft
  • Insulation needed (with 10% waste)72 sq ft

How to use the Duct Surface Area Calculator

  1. 1Choose round or rectangular duct and enter its dimensions.
  2. 2Enter the total length of the duct run.
  3. 3Use the surface area for insulation wrap, mastic sealant coverage or sheet metal takeoff.

Frequently asked questions

Why add a waste factor?

Overlaps, offcuts and fitting transitions typically consume 5-15% extra insulation material.

Does this include both ends?

No, this is just the lateral (side) surface area of the duct barrel, not the end caps.

About this calculator