What is 12 feet by 16 feet by 9 feet?

1 gallon of paint usually covers 350-400 sq. feet.

(12+12+16+16) x 9 = 504 Sq. feet of wall space. This is not including doors or windows. So it actually would be less. So subtract roughly 20sq. feet per door and roughly 15 sg. feet per window.

You would need around 1.5 Gallons of paint. So 2 gallons.

If you really only got 40 sq.feet that would be over 12 gallons of paint. Which would paint an entire mansion.

So $24 in paint. Plus supplies, rollers, edging brushes etc.

If you had no painting utensils you could probably get away with about $60-70 to buy paint and supplies.

(12 x 9)2 + (16 x 9)2= 504sqft (if 9 feet is the height) 504/40=12.6 gallons 12.6 round up to 13 gallons 13 x 11.99 = $155.87 or 12.6 x 11.99 = $151.07

I hope that is a math question and not for painting of your own room. If that is for painting of your own room. If its a math problem then yes 12.6 gallons which would be 13 gallons of paint since you can buy .6 gallons. If this is for your room in your house, then …What are you going to do with the extra 11.5 gallons of paint?