Measuring guide

How to Measure a Room for Painting

Three measurements and two counts are all a rectangular room needs. Odd shapes take a few more, and this guide covers those too.

What to bring

A 25-foot tape measure, or a laser measure for tall walls and big rooms
A notepad or your phone, with one line per room

Round to the nearest half foot. Paint is sold by the gallon, so an inch here or there never changes the order.

Rectangular rooms

Length and width. Measure along the floor, wall to wall.
Height. Floor to ceiling. Measure one corner; most rooms are level enough.
Doors. Count them. A standard 3' × 7' door is about 21 sq ft.
Windows. Count them. A typical 3' × 5' window is about 15 sq ft.
Ceiling. Note whether it gets painted. Its area is length × width.

Wall area = 2 × (length + width) × height − doors × 21 − windows × 15

For sliding patio doors, wide archways, or picture windows, measure width × height and subtract the real number instead of the standard size.

Sample measurement sheet

Room	L	W	H	Doors	Windows	Ceiling
Living room	18	14	9	2	3	Yes
Primary bedroom	14	12	8	2	2	No
Hallway	20	4	8	4	0	Yes

These columns match the estimator's room fields, so you can type a sheet straight in.

Rooms that aren't rectangles

L-shaped rooms

Split the room into two rectangles and enter each one. The open side where they meet gets counted as wall, so add it as an extra door or two to take that area back out.

Closets

Enter a closet as its own small room with its inside dimensions and one door. Closets take more time per square foot than open walls, so some painters price them flat.

Gable and vaulted walls

The triangle above the regular wall height is half its base times its rise.

Gable triangle = ½ × width of wall × (peak height − wall height) Example: ½ × 14 × (14 − 8) = 42 sq ft

Add the triangle to the room's wall area. In the estimator, the simplest way is to raise the room's height until the wall area matches.

Stairwells

Measure the tallest wall from the lower floor to the ceiling above it. Expect to price stairwells higher because they need planks or a ladder system.

Mistakes that cost money

Forgetting closets. They add up across a whole house.
Measuring only the main walls in an open floor plan. Walk the whole perimeter, including short returns and soffits.
Missing a ceiling height change. One room with a 10-foot ceiling adds 25% more wall area than the same room at 8 feet.

Got your measurements? Enter them and get gallons, labor, and a total in one step.

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