# How do I calculate ceiling pitch for a fan on a vaulted ceiling?

If you have a pitched ceiling, your ceiling fan will need to have a downrod that’s long enough to keep the sweep of the blades clear of the downward sloping ceiling. A ceiling’s pitch is defined as the amount the ceiling rises for every foot of width. (This might sound familiar if you remember calculating “rise over run” in middle school geometry.) Most homes have a ceiling pitch that falls into one of just a few traditional ratios, and these ratios are usually expressed as “X/12.” A “2/12” roof pitch rises two inches for every twelve inches it runs.

If you don’t already know your roof’s pitch, calculating it is relatively simple. Just measure the difference in height from the bottom of the slope to the top of the slope as well as the width of the slope (parallel to the floor, not parallel to the angle of the roof). Convert these measurements into inches and then reduce the ratio to an “X/12” fraction. (Hint: If you did this right and the home was built under standard procedures, “X” should be a whole number between 1 and 12.) Then, choose your downrod length from the chart below.