Chimney Capacity Calculator - Calculator Academy

Calculate chimney capacity, draft pressure and fireplace flue size from flue dimensions, height, temperatures and opening area in metric or imperial units.

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Chimney Capacity Formula

The following formula is used to calculate the chimney capacity for a given diameter and height.

V = (pi / 4) \times D² \times H

Variables:

V is the chimney capacity
D is the chimney diameter
H is the chimney height

To calculate the chimney capacity, multiply the square of the diameter by the height, then multiply by π/4.

What is a Chimney Capacity?

Chimney capacity refers to the volume of space within a chimney. Internal volume is a geometric measurement; it does not determine venting capacity or efficiency. The capacity is influenced by the diameter and height of the chimney, and it plays a significant role in ensuring proper draft and ventilation. Volume alone does not establish safe venting. The theoretical draft option approximates ideal air-column buoyancy; its optional flow estimate excludes actual system resistance, wind and appliance losses. Fireplace flue sizing compares clear internal area with shape-based masonry-fireplace ratios; verify locally adopted code and appliance requirements.

How to Calculate Chimney Capacity?

The following steps outline how to calculate the Chimney Capacity.

First, select Cylindrical volume and measure the clear inside diameter of the round flue (D).
Next, measure the height of the chimney (H).
Next, calculate the chimney capacity using the formula V = (π / 4) * D² * H.
Select Calculate. To solve a different geometric value, select Diameter from volume or Height from volume.
After inserting the values 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.

Chimney Diameter (D) = 1.5 m

Chimney Height (H) = 10 m. The internal cylindrical volume is approximately 17.6715 m³.