How Much Paint And Primer Do I Need For A 12x12 Room?

How Much Paint And Primer Do I Need For A 12×12 Room?

Getting the right amount of paint and primer can save you an unhelpful trip to the hardware store in the middle of a project.

That being said, unless you’re painting the whole house one color, you don’t want to overbuy.

Paint and primer can be costly, and buying too much is an extra expense that you don’t need.

Planning ahead and buying the right amount of paint and primer will save you money and frustration.

The following information will tell you how much paint and primer you will need for a 12×12 room along with some tips for using it efficiently.

woman on a ladder holding a paint roller

How Much Paint And Primer Do I Need For A 12×12 Room?

In a room with flat 8-foot walls, you will need 2 gallons of both paint and primer to cover a 12×12 room. You may not use all 2 gallons, but it’s great to have a little bit extra just in case. Also, primer doesn’t cover as much area as paint so having 2 gallons of each will ensure you have enough for the project.

Plan ahead of time and purchase 2 gallons of paint and primer instead of 1. If you only buy 1 gallon and end up needing 1.5 or 2 gallons to finish the project, you will be forced to go back to the hardware store to buy another gallon.

This will leave you with extra paint and primer that you don’t need and is an additional expense.

How to Use Primer Efficiently

Once the walls are brushed, washed, and patched, you may be able to simply prime over your patches. This will not work if you

  • are covering a saturated accent wall color with a lighter shade
  • are covering a strong paint pattern or finish
  • have a lot of patches and repairs to make

If you are just covering the patches, invest in a micro-foam roller that you can use to feather out the edges of the primer you put over the patch. Avoid using a brush if at all possible.

First of all, primer can be very hard on a good brush. Secondly, cheap brushes will leave brush marks and even hair in your patch.

Should you be painting a heavily textured wall, such as palm plaster, it may be difficult to wash the walls. Do make sure you brush them fully with a clean broom to take away as much dust as possible.

In such a case, you’ll get the best results by priming the walls from floor to ceiling for a clean finish.

Be aware that some primers can be tinted to stock colors. If you’re planning a very rich or saturated color on your walls, it may be worth it to use a tinted primer.

applying primer using a roller

However, if you’re just painting one accent wall, a white primer will be fine.

As a general rule, you shouldn’t have to apply two coats of primer unless you are covering a very intense shade or a large stain.

Check the recommended dry times and let your primer cure fully before you add a second coat to a stain or color that bleeds through.

Check out: How long does it take to paint a 12×12 room?

A Word About Masking

Primer is high in resins and low in pigment. Where it hits, it sticks. Cover your skin as much as possible for easier cleanup. Pay special attention to your hair; getting primer out of long hair can be especially problematic.

If you’re painting ceilings as well as walls, use a face shield to protect your mouth, nose, and eyes.

How to Use Paint Effectively

Once your walls are fully primed and the primer has completely cured, you’re ready to paint. It is critical that you not rush this process.

Check the temperature requirements for your primer and the time needed to fully cure before you start your top coat to apply your chosen color.

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To get a terrific-looking top coat over white primer, start in a corner with, if possible, a full wall with no windows or doors to break up the painting process.

Should you see that your chosen color will need more than one coat early in the process, you can go get more before it’s a crisis. Use a brush to paint down the corner, edge the corner where the ceiling meets the wall, and edge above the baseboard.

man painting a large wall

Masking tape will protect your baseboard and a masking shield that you hold against the ceiling will protect that corner and keep it tidy.

Give yourself a wide enough cut zone to give you plenty of rolling space; I usually try to cut a full wingspan, from fingertip to fingertip.

You’ll probably need a ladder to do the ceiling cut. You can avoid rolling too far ahead by setting the ladder up for your next cut and rolling from the corner to the ladder.

Keep rolling simple. If your walls are flat, use a 3/8-inch roller. If your walls are heavily textured, you may have to go up to a 3/4 or 1-inch roller.

This will mean burning a lot of paint in the roller, but you’ll get a much nicer finish if you don’t skimp on this.

Roll a “V” from waist to ceiling from left to right, then roll back, right to left to fill in and use all the paint that you just put on the wall. Pay attention to your hands and your eyes.

If you notice gaps in coverage or feel yourself pressing to push paint out of the roller, get more paint out of the pan.

In a room with flat 8-foot walls, you will need 2 gallons of both paint and primer to cover a 12×12 room.

As you roll on the paint, check your cut line at the ceiling for drips. It’s very easy to miss these and can really make a freshly painted wall look shabby if you have a long, dried drip that formed after you rolled that section of the wall. The rolling step is your second look. Cut first!

Roll from top to bottom. Once you have the first “V” filled in, move to the bottom part of the wall and work the same pattern.

If you have a hard time bending or working on the floor, you can roll the top first from corner to corner and then roller the bottom section of the wall.

Just keep an eye out for drips and always work top to bottom.


A good cutting brush should always be cleaned thoroughly after you finish the job.

Any remaining paint will make your brush stiff and will take away the flexibility of the bristles to give you a good cut the next time you paint.

Tools that are used for primer will not be a great choice for use with paint in the future.

While I have been able to clean a roller well enough that I can later use it for primer, I have not gotten a good paint job out of a used roller.

Rollers are designed to hold and disperse paint. When trying to clean them, you’ll find the “hold” feature to be a real challenge.

new paint roller

Microfiber rollers are generally too small to paint a whole wall (unless you really like to roll paint) but they are terrific for

  • covering sheetrock patches with primer
  • filling in paint around light switches and under outlets
  • wooden trim paint jobs

Do be aware that microfiber rollers don’t actually move a lot of color from bucket to surface. If you’re covering a deeply saturated shade, you’ll still need to prime.

However, these little rollers offer a lovely, smooth finish when applying trim paint in particular.

Be prepared for some painting tools to be disposable. Take very good care of your spindles, but go ahead and discard rollers that are impossible to clean.

Be religious about cleaning your good brushes and try to prime with small rollers rather than cheap brushes. You’ll be much happier with your finish.

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