Estimate section mass from material volume and mass density, using illustrative shell geometry, custom dimensions or a known material volume. Hollow blocks and separately unmodeled components require additional accounting.

Illustrative uniform rectangular shells; dimensions and densities are assumptions, not standard chimney specifications.

Include the full section being weighed, not only height above the roof.

Use actual density

Blank uses the selected illustrative density. Use assembly density if it includes block cores or mortar.

Chimney Weight Formula

The calculator estimates mass as material volume multiplied by mass density. Shell modes subtract one rectangular flue opening; the known-volume mode supports the historical 120 lb/ft³ example.

CHIM = CV × rho

Variables:

  • CHIM is the Chimney Weight (lb)
  • CV is material volume excluding voids (ft³); rho is mass density (lb/ft³) 

Multiply material volume in cubic feet by the appropriate density in lb/ft³. The historical 120 lb/ft³ and shell-mode densities are illustrative assumptions, not universal material or product values. Account for block cores, mortar, grout, liners, caps and other components as applicable.

How to Calculate Chimney Weight?

The following steps outline how to calculate the Chimney Weight.

  1. First, determine the material volume excluding the flue and other voids (ft³). 
  2. Next, gather the formula from above: CHIM = CV * rho.
  3. Finally, calculate the Chimney Weight.
  4. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Material volume = 20 ft³; assumed mass density = 120 lb/ft³

CHIM = CV × rho = 20 × 120 = 2,400 lb (1,088.62 kg)