How to Find the Size of a Home AC Duct
Knowing the size of a home AC duct is necessary for several situations. You'll need the size if you want to build a soffit around the duct. Or, if the duct is in the way of something you're installing, you'll need to resize the duct. You might even want to insulate the duct, and you'll need to know the duct's size to accurately cut the insulation. Whatever the reason, it's really easy to find out the size of a home AC duct. Does this Spark an idea?
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Instructions
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Instructions
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1
Locate the AC duct you want to measure. If possible, remove anything that's around the duct to get an accurate measurement.
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2
Determine if your duct is round or square. For round ducts, move to Step 3. For square ducts, measure the two adjoining sides. Add these two measurements together to get your duct's size. (For example, if you measure a 12-inch side and an 8-inch side, your duct is 12 by 8.)
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3
Measure around the round duct with your tape measure. You're measuring the circumference, which helps you find your round duct's dimension.
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4
Divide the measurement from Step 3 by pi, which is 3.14. This gives you the duct's diameter. (For example, if the circumference is 25 1/8 inches, and you divide that by 3.14, you get 8, which is the diameter of your duct in inches.)
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Tips & Warnings
Sheet metal duct is extremely sharp and can cause cuts when working near ducts. Wear gloves at all times to prevent possible injury.
