Estimating the amount of paint you will need to paint your house is not rocket science.
But it can be tricky if you do not know the basics and the right measuring process.
Too little, and you wind up buying more than expected. Too much, and you have wasted your money with useless paint that is leftover.
Well, if you are planning to paint your house and wondering how much paint you will need, let’s start with some estimates and calculations.
As a general rule, you will be using about 1 gallon of paint for every 325 to 350 square feet of surface area you need to paint.
Now, this much paint will usually be enough for a small room like a bathroom.
But what if you want to cover around 1,000 square feet, which may include applying at least two coats on the interior as well as exterior walls along with all the ceilings in your home (including upstairs, downstairs, basement, etc.)?
At 325 sq. ft. per gallon, you will need precisely over 3.08 gallons of paint to cover the 1000 sq. ft. area. For applying a second coat, it will be again a little less than 3.08 gallons.
So, for two coats, it will be around 6.16 gallons of paint, which you will need to completely cover a 1000 sq. ft. area.
I’ve painted thousands of homes in my lifetime ranging from 1000 sq ft to 10,000 sq ft.
And here is what I found when I applied two coats of paint, including all the interior and exterior surfaces.
Remember – you may require a bit extra depending on the type of paint, paint formula, increased number of coatings, or the wall texture you may require.
If your walls are bare new, not plastered, and dry, you may require even more.
Having said that, you do not want the excess amount to be too much. Otherwise, you will have cans of paint sitting around your home doing nothing.
Also, remember that it will generally depend on the paint coverage you need for your house’s interiors and exteriors.
So, let’s dive into some of those details as well…
How Much Paint Do You Need for Interiors?
This is a difficult question because interiors may require you to paint items apart from the walls.
You can start with the manufacturer’s recommendations, usually found on their website and sometimes on the side of the cans.
But it’s better to add all the room areas and items you want to cover and then calculate how much paint will be needed.
However, please bear in mind that the actual coverage rate can vary depending on the brand and the surface that needs to be covered.
For example, if you are covering a wall in a 10×10 sq ft room that has already been painted and do not want to remove the underlying paint, the manufacturer’s coverage rate should be about right.
However, if you are covering an unpainted area, you may need about two times the amount of paint.
The difference is that you will need additional coats of paint to cover the unfinished area thoroughly and to the expected finish.
A general guess for interiors starts by assuming a standard room that is 12’ x 12’ x 9’. From there, the following calculations can be made;
|Interior Area||Paint Quantity|
|One Wall||1 Gallon|
|Feature Wall||½ Gallon|
|Woodworking or Trim||¼ Gallon|
Naturally, the larger the room (like 10×15 or 12×12 or 12×15), the more needed paint.
Add whatever paint is needed for larger rooms, then the smaller ones (they will need a bit less). This should give you a rough amount.
It’s better to have a little too much paint compared to too little because of the lower price per liter.
Plus, you may be able to use the excess paint for other areas, such as a feature wall or painting items around the home.
How Much Paint Do You Need for Exteriors?
Generally speaking, exterior walls are usually easier to calculate the amount of paint needed compared to interiors.
Because the surface areas of exteriors are usually flat and have fewer corners (or unique angles) compared to interior surfaces.
However, the exterior areas like bricks are subject to far more stress due to the sun’s ultraviolet rays and erosive elements such as wind, rain, hail, and snow.
This can be compensated by the toughness and durability of the paint used for exterior surfaces.
In this case, the same rule as for interior surfaces applies.
Namely, if you are covering surfaces that have already been painted and do not remove the underlying paint, the coverage area should be very close, as indicated by the manufacturer.
On the other hand, if you remove the underlying paint or the area has yet to be painted, you will probably need twice as much to add the extra coat.
The standard guide for the amount of paint needed for exteriors includes the following;
|Exterior Area||Paint Quantity|
|Walls||8 to 10 Gallons|
|Front Door||¼ Gallon|
|Eave Linings w/Carport||2 to 3 Gallons|
|Gutters, Fascia, etc.||1 Gallon|
Any additional areas that need painting will also have to be accounted for.
Factors to Consider When Doing the Calculations
Remember that the calculation above is based on a typical single-story house.
You may need more if you have a larger home or less if you have a smaller than the standard house.
While getting the measurement, ensure that you measure the length and height correctly, especially when getting the height from the floor to the ceiling.
The advantage of using these online paint calculators is that it helps you to get an estimate when you do not want to paint the doors or windows.
You can simply fill in the measurements of your doors and windows. And the calculator will help in subtracting the square footage areas of the windows and doors.
The estimate of paint quantity you will get using these tools assumes that you will apply two coats of paint.
So, if you need to apply more than two coats, add to the quantity while buying from your paint supply store.
How Can You Save the Cost when Buying Excess Paint?
Knowing how much paint you need before you make the purchase may save you a considerable amount of money.
Another way to alleviate the cost of having extra paint around is to purchase an excess liter or gallon and not have it tinted.
This can lower your paint job costs, particularly if you require buying a premium paint product in large quantities, like for 2200 or 3000 square feet areas.
If it turns out you need the extra paint for your project, you can purchase the tint from the paint store and mix it in.
Just in case – you do not use it, you can tint the paint the way you want for another project in the future.
The bottom line
Considering that the average liter of good quality paint can run $35, which becomes less per liter with the more paint you purchase, understanding how much you need will make a considerable difference in staying within your budget.
Using an online paint calculator or a paint estimator tool is one of the smartest and easiest ways to figure out how much paint you will need for your interior & exterior paint projects.
Remember that there is no exact science to this, but overall you should err on the side of excess to ensure that you have enough paint to do the job.
It also helps if you have other uses for the leftover paint.
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for over a decade serving customers in areas such as Charleston, Mount Pleasant, Beaufort, and Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques implemented in his profession. You may read more about him here or get in touch with him here.