Paint Calculation: How Much Paint Do I Need

At the finishing stage of your residential building project, this question will come to your mind “How much paint do I need?”.

So, in this post, I’ll show you the process of paint calculation for walls and ceilings.

You’ll also learn to calculate the required putty quantity.

After learning this, you can calculate the required paint quantity for your whole project.

So, let’s learn.

How Much Paint Is Needed For The Walls Of A Bedroom?

I’ll show you the paint calculation process of a bedroom’s wall here.

Once you’ve learned the process, you’ll be able to calculate the required paint quantity for all of the rooms of an apartment, and eventually for the whole project.

Let’s say, this is our bedroom to be painted:

To calculate paint quantity…

First, Get The Gross Painting Area Of Walls.

The formula is,

= Length of walls × Height

Here,

Length of walls is,

= 2 × (10′ + 12′)

= 44 feet.

And, the height is = 9′-6″

So the gross painting area is,

= 44 × 9′-6″

= 418 square feet.

But, Here is a beam in the bedroom:

In some rooms, you’ll get beams like this.

And, you need to add the beam bottom portion to the gross painting area.

In our example, it is.

= 5″ × 12′

= 5 square feet.

So, the total gross painting area of the bedroom’s walls is,

= 418 + 5

= 423 square feet.

Next, Calculate The Area Of Openings.

Here we have two openings — a window and a door.

The area of the window opening is,

= 5′-0″ × 4′-6″

= 22.50 square feet.

And, the area of the door opening is,

= 3′-4″ × 7′-0″

= 23.31 square feet.

So, the total opening area is,

= 22.50 + 23.31

= 45.81 square feet.

Now, Calculate The Net Painting Area

The formula is,

= Gross painting area — Opening area

= 423 — 45.81

= 377.19 square feet.

Say, 378 square feet.

This is the area you need to calculate paint for.

Finally, Calculate How Much Paint You Need For The Area.

The formula is,

= Net painting area ÷ Coverage area of paint per liter.

The coverage of paint varies depending on the surface condition and manufacturer.

Generally, one-liter paint covers somewhere 40 to 50 square feet. However, you should check the manufacturer’s information.

For the sake of our calculation, Let’s take 45 square feet per liter.

So, the required paint quantity is,

= 378 ÷ 45

= 8.4 liters.

This is for one coat paint only.

To get the smooth paint finish, you need at least two coats of paint.

So, for two coats, the required paint quantity is,

= 2 × 8.4

= 16.80 liters.

This is the required paint quantity we need for our example bedroom.

But,

How Much Paint Is Needed For The Ceiling?

Obviously, you aren’t going to use the same paint on walls and ceiling.

The paint on the ceiling is often different than the walls.

So, let’s learn the process of paint calculation for the ceiling.

Actually, the process is the same as the wall paint.

You first need to…

Calculate The Gross Painting Area.

The formula is,

= Length × Width

= 10′-0″ × 12′-0″

= 120 square feet.

This is actually the net painting area for our ceiling as we don’t have any openings in the ceiling.

[NOTE: But sometimes, you’ll have some columns’ portion and beam portions to be deducted from the gross painting area.
For sake of the simplicity of this post I just didn’t put them in our example.
I think you got this.]

So, you just need to…

Calculate the required paint quantity…

…For 120 square feet of painting area.

And, the formula is,

= Net painting area ÷ Coverage area of paint per liter.

Let’s assume the coverage area of paint per liter is 45 square feet.

So, the required paint quantity for one coat is,

= 120 ÷ 45

= 2.66 liters.

And for two coats,

= 2 × 2.66

= 5.33 liters.

As you now know the process of paint calculation, let’s see…

How To Calculate The Required Quantity Of Putty

Before painting, you need to apply putty on a new surface.

So, it’s time to learn the process of putty calculation.

The process is the same as the paint calculation.

Let’s say, you need to calculate the required putty quantity for the walls of our example bedroom.

For that:

First, Calculate The Net Painting Area

We calculated this before, at the time of paint calculation.

And that is 378 square feet.

Now, Calculating The Required Putty Quantity

And, the formula is,

= Net painting area ÷ Coverage area of putty per kg.

The coverage area of putty is 12 — 15 square feet/kg for two coats and 8 — 12 square feet/kg for three coats.

Let’s say, you’re going to apply three coats of putty on the surface and the coverage area of putty is 10 square feet per kg.

So, the required putty quantity is,

= 378 ÷ 10

= 37.80 kg.

That’s it!

Conclusion

Calculating paint quantity is easy.

Right?

You just need to get the net painting area and divide the area with the coverage area of paint per liter.

Most of the manufacturers show the coverage area of the paint on their product’s label. You can get the information from there.

Your Turn:

Have you experimented ever with how much area can cover a liter of paint?
If you have please share that in the comments below…