Estimating the amount of paint, you will need to paint your house, is not a rocket science.
But it can be tricky if you do not know the basics and 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.
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 of paint will usually be enough for a small room like a bathroom.
But want 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 exactly 3.08 gallons of paint to cover 1000 sq. ft. area.
Keep in mind that you may require a bit extra depending on the paint formula, number of coating, or the wall texture you may require.
If your walls are 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.
Well, if you are planning to paint your house and wondering how much paint will you need, let’s start with some estimates and calculations.
Remember, it will generally depend on the coverage of paint you need for the interiors and exteriors of your house.
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 will need to add up the rooms and items you want to cover and then calculate how much paint will be needed.
You can start with the manufacturer’s recommendations which are usually found on their website and sometimes on the side of the cans.
However, 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 you do not want to remove the underlying paint, then the manufacturer’s coverage rate should be about right.
However, if you are covering an unpainted area, then you may need about two times the amount of paint.
The difference is because you will need additional coats of paint to fully cover the area properly.
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 paint will be needed.
You should start by adding up all rooms that need to be painted.
For larger rooms, add whatever paint is needed while smaller rooms will need less. This should give you a rough amount.
It is 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.
The surface areas of exteriors are generally flat and have fewer corners (or unique angles) as compared to interior surfaces.
However, the exterior areas like bricks are subject to far more stress due to the ultraviolet rays of the sun along with erosive elements such as wind, rain, hail, and snow.
This can be compensated by the toughness and durability of the paint that is used for exterior surfaces.
In this case, the same rule as for interior surfaces applies.
Namely, that if you are covering surfaces that have already been painted and you do not remove the underlying paint, then the coverage area as indicated by the manufacturer should be very close.
On the other hand, if you are removing the underlying paint or the area has yet to be painted, then you will probably need twice as much to add the extra coat.
A general 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 have to be accounted for as well.
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 house.
While getting the measurement, make sure that you measure the length and height properly, especially when getting the height from the floor to the ceiling.
The advantage of using these online paint calculators is it helps you to get the 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 want to apply more than two coats you will need to add up to the quantity while buying from the 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.
This is especially true if you are going with a higher-quality and thus, higher-priced paint.
One 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 down your painting costs much if you want to buy a premium paint product in large quantities.
Just in case – you do not use it, then you can tint the paint the way you want for another project in the future.
If it turns out you need the extra paint, then you can purchase the tint from the paint store and mix it in.
The bottom line
When you consider 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 more than a decade to serve the customers in areas such as Charleston, Mount Pleasant, Beaufort, Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques that are being implemented in his profession. You may read more about him here or get in touch with him here.
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