Chair Rail Calculator
Chair rail is a horizontal molding that runs around a room about a third of the way up the wall, protecting plaster and adding a decorative line. To buy the right length, take the room perimeter, subtract the door openings where the rail stops at the casing, and add a waste allowance for miter cuts. Enter the perimeter in feet, the door opening width to subtract, a waste percentage, and the stick length. This calculator returns the net length, the total with waste, and the number of sticks to buy.
Chair rail formula
Net length = perimeter - door openings
Total with waste = net length * (1 + waste / 100)
Sticks to buy = ceil(total with waste / stick length)
Subtract doorways where the rail stops at the casing. The waste factor covers miter cuts. Sticks round up to whole pieces.
Chair rail tips
- Chair rail commonly sits 32 to 36 inches above the floor.
- Subtract doorways; decide per design whether to subtract windows.
- Allow more waste for rooms with many corners or window returns.
- Buy whole sticks; partial lengths are not sold.
- ICC and HUD residential standards govern interior finish trim in the US.
Chair rail: frequently asked questions
How do I calculate chair rail length?
Add the wall lengths to get the perimeter, subtract the width of door openings the rail does not cross, then add a waste allowance for miter cuts. Chair rail runs around the room at a fixed height, breaking at door casings.
At what height is chair rail installed?
Chair rail is commonly placed about 32 to 36 inches above the floor, roughly a third of the wall height, to protect walls from chair backs. The exact height does not change the length calculation, which is based on perimeter.
Do I subtract doors and windows for chair rail?
Subtract doorways where the rail stops at the casing. Windows are typically not subtracted because chair rail usually runs across beneath the window, though you can subtract them if your design returns the rail into the window trim.
How much waste should I allow for chair rail?
A 10% allowance covers miter cuts at corners and offcuts. Rooms with many corners or returns into door casings benefit from a slightly higher allowance. This calculator lets you set the percentage.
How many sticks of chair rail do I need?
Divide the total length including waste by the stick length, commonly 8 feet, and round up to whole pieces. This calculator reports both total feet and the rounded number of sticks.
Official sources
- U.S. Department of Housing and Urban Development: Residential construction guides.
- U.S. General Services Administration: Design and construction standards.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.