How much acrylic paint do I need to fill a 2x2 meter canvas?
Get yourself a 10 x 10 centimetre square of your canvas and paint a test piece. Once you are happy with your painting measure the amount of paint that was used and then multiply it by 400. That is how much paint you will need to create the same image on a two by two meter square canvas.

2m = 200 cm

200 cm x 200 cm = 40 000 cm^2

10cm x 10 cm = 100 cm^2

40 000 cm^2 / 100 cm^2 = 400 

Your 10 cm^2 canvas is 400 times smaller than your 2 m^2 canvas.

Going the other way, you would have to scale the test piece by 400 times for it to be the same size as your desired canvas.

Oh, and you can determine the amount of paint used by weighing your canvas (the 10 x 10 cm) one before and after painting. The difference in weight is the amount of weight added by the paint. Multiply that by 400 and you will have a good estimate for the amount needed.

Experienced carpenters add 20% for wastage. Carpenters are smart, they know things will go wrong.

So a safe number would be 480 times the amount.

400 x 1.2 = 480

How much actual paint could this be?

Let's say, it takes the artist the equivalent of a quarter of a 2 fl. oz. tube of paint to cover the 10 cm^2 canvas. That's 0.5 fl. oz. of paint to do the painting with.

0.25 x 2 fl. oz = 0.5 fl. oz.

Since the 2 m^2 canvas is 400 times bigger than the 10 cm ^2 canvas you would need a total of 200 fl. oz. to do the same painting as your test piece on the larger size canvas.

0.5 fl. oz. x 400 = 200 fl. oz.

That means you would have to purchase 100 tubes of the 2 fl. oz. paint tubes.

100 x 2 fl. oz. = 200 fl. oz.

Now I did say you need to account for wastage. Assuming 20% of your paint gets wasted. then the number of tubes needs to grow by 20%. That's 120 tubes of paint.

100 * 1.2 = 120 tubes of 2 fl. oz paint tubes.

Now lets say those 2 fl. oz. paint tubes cost $10 USD each. To buy 120 tubes at $10 USD each would cost you a total of $1200 USD.

120 * $10 USD = $1200 USD.

That's $1200 in paint alone.

The next time you go to a gallery show and see all those large paintings hanging on the wall know that the artist had to shell out a hell of a lot of money out of their own pocket to get those paintings made.

The greatest investment artists make are in themselves.