Enter = copy
Code references are general guidance (IRC 2021 / NFPA 211 / NFPA 54). Confirm against the code edition your jurisdiction has adopted. The inspector is responsible for the final report.
Vent connector rise & run
Appliance
Connector pipe
ftin
inches
How much higher the pipe is where it enters the chimney than where the horizontal section starts.ft
From the appliance's draft hood or flue outlet up to the top of the chimney or vent.Hearth extension size
in widein tall
in frontin each side
For the side, enter the shorter of the two sides.Chimney height (3-2-10 rule)
ft
Measured from the highest point where the chimney passes through the roof.ft
How much higher the chimney top is than the tallest part of the building (ridge, wall, dormer) within 10 ft horizontally. Enter a negative number if it's lower.Masonry fireplace flue size
in widein tall
Flue shape
×in
in
sq in
Clay tile corners make the real opening smaller than width × depth. Use the liner's listed net area when you have it.Calculators use IRC 2021 R1001.10 (hearth extensions), R1003.9 (chimney termination), R1003.15.1 (fireplace flue area, Option 1) and NFPA 54 / IRC G2427.10 (vent connectors). Confirm against the appliance listing, manufacturer's instructions and local code.