Dryer vent length & fire-risk checker
Measure the run, count the elbows, tell us what it’s made of and where it ends. You’ll get the developed length against the 35 ft code limit, a risk read with the reasons, what to do next and what to tell the pro.
Count from the back of the dryer to the outside hood. Not sure of the length? Pace it off along the wall and add any rise to the attic or roof.
Measure the run, tick what you see.
Length, elbows, duct material, where it ends, last cleaning and symptoms. The read updates as you go. The code limit is 35 ft of developed length, counting each 90° elbow as 5 ft and each 45° as 2.5 ft.
Get a free dryer vent estimateOr call (888) 996-7488
We match you with a vetted local pro. A rule-of-thumb check, not an inspection.
Dryer vents: common questions
How long can a dryer vent be?
The International Residential Code (M1502.4.5.1), which the Florida Building Code, Residential, follows, limits a dryer exhaust duct to 35 feet of developed length. Each elbow counts toward that: a 4-inch 90° elbow as 5 feet and a 45° elbow as 2.5 feet. The dryer manufacturer’s installation instructions may allow a longer run (M1502.4.5.2). Verify with your city’s building department if the run is being changed.
What is “developed length”?
The straight duct plus an allowance for every bend, because each elbow slows the air about as much as several feet of straight pipe. This tool adds 5 feet per 90° elbow and 2.5 feet per 45° to the straight length you enter.
Is foil or plastic dryer duct allowed?
Plastic duct is not: the code calls for smooth metal duct, and plastic sags, traps lint and burns. A short flexible transition piece between the dryer and the wall is allowed only when it is listed for dryers, no longer than 8 feet, and not run inside a wall, ceiling or floor (M1502.4.3).
Can a dryer vent end in the garage or attic?
No. A dryer exhaust must terminate outside the building (M1502.3). Venting into a garage, attic or crawl space piles lint and moisture against the structure, and with a gas dryer can put carbon monoxide indoors.
How often should a dryer vent be cleaned?
Once a year for most households; every 6 months with a large family, pets, a long run or a roof termination. The U.S. Fire Administration names failure to clean the vent as the leading cause of home dryer fires.
Is this an inspection?
No. It is a rule-of-thumb read built from the code’s length table and the signs of a clogged vent. We match you with a vetted local pro who checks the run on site and gives you a free estimate before any work starts.
More about dryer vent cleaning and replacement, or see all free tools.