How to Calculate the Cost of Painting a House

When I was trying to figure out how much it would cost to paint a house I realized there is no single number you can just look at.

It depends on the size of the walls
the number of rooms
the type of paint
and probably the biggest one
whether you are doing the work yourself or paying someone.

I actually painted my own house because I wanted to keep the cost down. It took more time than I expected but I saved quite a bit on labor.

So if you are trying to calculate the cost before buying anything this is the way I would do it.

Start with the walls

First you need to know how much wall you are actually going to paint.

For a simple room you can use this:

Wall area = (Length + Width) × 2 × Height

For example if the room is 15 feet long and 12 feet wide and the walls are 8 feet high:

(15 + 12) × 2 × 8 = 432 square feet

That is your basic wall area.

But you probably have doors and windows. So you should subtract them.

If the doors and windows take up around 60 square feet then:

432 – 60 = 372 square feet

Now you have a much better idea of the actual area that needs paint.

Don’t forget the ceiling

If you are painting the ceiling too it is easy to calculate.

Just multiply the length by the width.

15 × 12 = 180 square feet

So in this example you would have 372 square feet of walls plus 180 square feet of ceiling.

That gives you 552 square feet of paintable area.

How much paint do you need?

This part can be a little confusing because different paints cover different amounts of area.

Check the coverage written on the paint can. A common range is around 350 to 400 square feet per gallon but I would always use the number from the actual product you are buying.

Let’s say your paint covers 350 square feet per gallon and you want two coats.

552 × 2 = 1,104 square feet

1,104 ÷ 350 = about 3.15 gallons

So I would probably buy 4 gallons rather than trying to get away with exactly 3.15.

Running out of paint halfway through the job is not fun.

Primer can add to the cost

If the walls are new or they have a lot of repairs you may need primer.

You might not need primer for every repainting job but it can make a big difference when the surface is new or when you are changing from a dark color to a much lighter one.

So when you make your budget don’t forget to include it.

Then there are the small things

This is where I think people sometimes underestimate the cost.

Paint is not the only thing you buy.

You may need brushes
rollers
paint trays
masking tape
sandpaper
filler
drop cloths
and maybe a ladder.

None of these things looks expensive by itself but together they can add a decent amount to the final bill.

What about labor?

This can completely change the total cost.

If you hire someone you need to add the labor to your calculation.

For example you could have something like:

Paint: $300
Primer: $75
Painting supplies: $60
Wall preparation: $100
Labor: $700

Total = $1,235

These are just example numbers of course. Prices can be very different depending on where you live and the condition of the house.

When I painted my own house I did most of the preparation and painting myself. I spent more time on it but I didn’t have to pay the labor cost.

For me that was the biggest saving.

A simple way to calculate everything

If you just want a basic formula you can use:

Total Painting Cost = Paint + Primer + Supplies + Preparation + Labor

And if you are doing the work yourself you can remove the labor part.

You should also leave a little extra money for unexpected things. Maybe you find a wall that needs more repair than you thought or you need another can of paint.

That kind of thing happens.

One mistake I would avoid

Don’t calculate the amount of paint based only on the floor size of the house.

A 1,000 square foot house doesn’t necessarily need the same amount of paint as another 1,000 square foot house.

One might have high ceilings and lots of walls. Another might have an open layout with fewer walls.

The actual wall and ceiling area is what matters.

If you want a quicker calculation

If you don’t feel like doing all the math yourself you can use a house paint calculator.

Enter the room dimensions and the calculator can help estimate the paintable area and the amount of paint you may need.

I like using a calculator for this because it is very easy to forget a room or accidentally calculate one wall twice.

Final thoughts

Painting a house doesn’t have to be complicated to calculate.

Measure the walls
subtract the doors and windows
add the ceiling if you are painting it
figure out how many coats you need
then add paint primer supplies and labor.

And if you are doing the painting yourself don’t forget to count the supplies even though you are saving money on labor.

I painted my own house mainly to save money and honestly that worked pretty well. It just took more time and patience than hiring someone.

If you are planning to paint your house soon I would measure everything before buying the paint. It only takes a little extra time and it can save you from buying way too much.

Frequently Asked Questions

How do I calculate the wall area?

Multiply the room perimeter by the wall height. For a rectangular room the formula is (Length + Width) × 2 × Height.

Should I subtract doors and windows?

Yes. If you want a more accurate estimate you should subtract the area of doors and windows from the total wall area.

How many coats of paint should I use?

Two coats are common but it depends on the paint and the condition and color of the wall.

Is it cheaper to paint a house yourself?

Usually yes because you are saving on labor. But you need to consider the time and effort involved.

Should I buy extra paint?

I would. Having a little extra is better than stopping in the middle of the job because you ran out.

If you are planning to paint your house soon and don’t want to spend time doing all the math yourself you can use our House Paint Calculator. Just enter the measurements and it will give you a quick estimate of how much paint you may need.