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Calculate chimney height with our free calculator. Use the IRC 3-2-10 rule, roof slope, elevation, and optional NFPA 211 check.
A chimney needs the right height to work well. It must clear the roof and nearby parts of your home. The right height also helps smoke move out with ease.
Our Chimney Height Calculator makes this task simple. You can find the required chimney height in seconds. It uses two methods based on IRC R1003.9. You can choose roof slope or roof elevation.
The tool also offers an optional NFPA 211 height check. It helps you check the height above your stove or appliance outlet.
The IRC 3-2-10 rule sets the basic chimney height. It says a chimney must rise at least 3 feet above the roof. It must also rise 2 feet above any roof part within 10 feet.
First, find the roof slope:
Roof Slope (S) = Roof Rise ÷ 12
Then find the roof height difference:
Height Difference (ΔH) = S × Horizontal Distance
Required Chimney Height (Hr) = MAX(3, 2 + ΔH)
If the ridge is over 10 feet away, this calculator uses 3 feet as the minimum projection.
Use this method when you know both roof heights.
Required Chimney Height (Hr) = MAX(3, Ho + 2 − Hp)
Here, Ho means the highest nearby point. Hp means the roof height at the chimney opening.
Total Chimney Height (Ht) = Base-to-Roof Height (Hb) + Required Height (Hr)
The calculator checks the height above the appliance outlet.
NFPA Check = Pass when Hn is at least 5 feet.
This check does not change the main chimney height result.
Our online chimney height calculator is easy to use. Follow these five steps.
Choose a method: Select roof slope or roof elevation.
Enter roof details: Add the roof rise and ridge distance, or both roof heights.
Select units: Choose feet, inches, meters, or centimeters.
Add extra details: Enter the base-to-roof height if you need total height. You can also enable the NFPA check.
Calculate: Submit your values to see the chimney height and calculation details.
Let's use a simple wood stove home as an example.
Suppose the roof has a 5:12 slope. The chimney sits 6 feet from the ridge. The base-to-roof height is 8 feet.
First, find the roof slope:
S = 5 ÷ 12 = 0.4167
Next, find the roof height difference:
ΔH = 0.4167 × 6 = 2.5 feet
Now, find the required chimney height:
Hr = MAX(3, 2 + 2.5)
Hr = 4.5 feet
Finally, find the total height:
Ht = 8 + 4.5 = 12.5 feet
So, the required roof projection is 4.5 feet. The total chimney height is 12.5 feet.
The right chimney height helps keep your home safe. It also helps smoke leave the building. Our Chimney Height Calculator saves time and reduces manual work. Use the slope or elevation method to check your project.
For a wood stove chimney, also check the appliance guide. Local building codes may set extra rules. A qualified installer can confirm the final height.
Measure the roof slope or nearby roof heights. Then apply the IRC 3-2-10 rule. You can use our calculator to make this task easier.
It means 3 feet above the roof, 2 feet above nearby roof parts, and a 10-foot horizontal range.
Yes. Under the IRC rule, it must rise at least 3 feet above the roof where it passes through.
The height depends on your roof and nearby structures. The basic IRC rule sets a 3-foot minimum above the roof.
There is no single height for every home. Roof shape, flue design, and the stove guide all matter.
Yes. Chimney height can affect draft. A well-sized chimney helps hot gases rise and exit. But height alone cannot ensure good draft.
Yes. You can use our online chimney height calculator on a phone, tablet, or computer. No separate app is needed.