A precise paint job starts with accurately calculating how much paint you need for a room. Accuracy can help you avoid overspending on paint or making extra trips to the store for more paint. Taking a wall measurement for painting is something that any homeowner can do on their own without hiring a professional. However, homeowners with higher ceilings should consider hiring a professional if they have hesitations about climbing up on a ladder to get accurate ceiling or window measurements. Here’s an explanation of how to get a room paint estimate using simple tools.
Measuring walls
The first step in figuring out how much paint you need for a room is to calculate the room’s perimeter. Your room’s perimeter is the total distance of the outer limits of your walls. When used in conjunction with ceiling height, your wall perimeter total will help you figure out the total square footage of the room that needs to be painted.
You can measure your walls using a simple tape measure. It usually requires two people because one person will need to hold the base of the tape measure in place. You’ll need to do two measurements if your room is not a perfectly even box. Measure the room’s width by running the tape measure from one side of each wall to the other in a straight line. Measure the room’s length by using a tape measure to measure the ceiling height from the floor. We recommend that you measure room for paint twice to ensure accuracy.
Calculating square footage
The square footage of the room you’re painting is the number that will help you figure out how much paint you need to cover everything. Multiply width times height for each wall in the room to get the square footage. You will need to calculate square footage for each wall before combining the totals together to get your total square footage.
Subtracting doors and windows
Walls and doors in a room represent areas that do not need paint. By cutting them out of the equation, you can save money and reduce paint waste. Measure the length and width of every door, window, or other “break” in your walls that won’t be painted. You can multiply the length times the width to get the square footage. Finally, subtract the combined square footage from all doors and windows from the total square footage you previously measured. This number still won’t give you an accurate total for how much you need. Your room’s total square footage is just the starting point. To get the actual number, you’ll need to factor in paint coverage rates.
Understanding paint coverage rates
Paint coverage rate can vary based on the paint you purchase for your room. Paint coverage rate refers to the size of the surface area a gallon of paint can cover using single-coat application. Manufacturers generally tally coverage rates using a ratio of square feet per gallon. Standard interior paint generally works out to 350 to 400 square feet per gallon. Meanwhile, formulations that go on thicker might get you closer to 300 to 350 square feet per gallon. This includes glossy paints. If you’re shopping for primer, expect to get just 200 to 300 square feet per gallon because bare surfaces can soak up paint much faster.
If you’ve done all of the steps above, you should be able to calculate how much paint you need to buy for your room now. Just refer back to the square footage you calculated after accounting for doors and windows. If this leaves you with a number between 300 square feet and 400 square feet, you may only need one gallon of standard interior paint to get the job done.
Multiple coat considerations
Don’t forget to factor in how many coats of paints you’ll need to get the finish you want. In general, eco-friendly paint and low VOC paint require two coats for a preferred finish. However, your needs can depend on whether you’re using primer, repainting over the same color, or attempting to repaint over a much darker color.
Example calculation
Let’s wrap up this paint calculator guide with an example of how to add up a room’s square footage to determine how much paint is needed. We’ll use standard bedroom dimensions of rooms at 10 x 12 feet with 8-foot ceilings using standard interior paint.
Gallons Needed = [(Total Wall Square Footage of Room − Doors/Windows) ÷ Coverage per Gallon] × Number of Coats Needed
2 = [(352 − 50) ÷ 300] × 2
If trying to calculate all those numbers feels overwhelming, you can just do what most people do today by using the Paint Calculator. All you’ll need to get a precise total for how much paint you need to buy is an accurate measurement of your room’s dimensions.