How to Estimate How Much Paint to Order


Starting any home decor project is exciting. Full of ideas and project plans, it can be easy for the enthusiasm of the project to overtake the practical realities. Ever started painting a room and realized halfway through that you don’t have enough paint to cover all the walls? Or find that the room really needs a second coat of paint to look even? Or wrap up a project and find yourself with a gallon of paint you no longer need?

Avoid these emergency trips to the hardware store with a little forethought before you get going! Order the right amount of paint the first time by doing some simple calculations.


Do the math

Guessing your paint amount starts with some math. Multiply the length of the wall by the floor to ceiling height of the room. Do this for each wall you’re painting and then add those numbers together for the total square footage of your walls.

Simply put, the calculation is: height x length = square footage.

  • Don’t forget to include all the walls in the room, including small ones in alcoves or other indents.
  • If you’re calculating a triangular wall space from a slanted ceiling, halve the number you get to accommodate the shape.
  • Be sure to subtract the square footage of any doors and walls from that number using the same calculation.


How much paint to order

Calculate your needs

Once you have your square footage, you can assume that one gallon of paint will cover about 400 square feet of wall space. Remember that most paints will need two coats, and dark colors will sometimes need a third coat for even color distribution.


Consider the surface material

Every room is different, and so your paint needs may vary from space to space. Some materials and colors increase the demand for paint on a space, so do factor in your material and paint type when you’re estimating how much paint to buy.

  • If you’re painting drywall, expect that you’ll need more paint because the material is highly porous and will absorb a great deal before the color shows up on the walls.
  • If you’re working on a wall that has been heavily patched or if you’re covering up a darker color, you may also need more paint to cover everything effectively.
  • If you’re panting masonry such as brick or concrete, your paint will be absorbed much quicker by the porous material, so you’ll need more paint for that as well. Use generous amounts of color to give it some sticking power.


Paint cans with paint

Allow for drying time

This is a secondary tip, but we recommend allowing for drying time before you decide that a room is fully painted. You may finish painting a room and think the color is opaque enough, but it may look very different after a few hours of drying time. You may realize that some areas have been neglected and need another coat. This is especially true of glossy paint.

Don’t make any final decisions until the paint has dried for at least six hours.


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