How much concrete do I need for a 12 by 12 3 inch thick concrete patio?

12 x 12 x .25 = 36 cu. ft.

There are 27 cu ft in a yard, so you have 1.33 yards. Order 1-1/2 to be sure you have enough. Hope this helps.

I agree with Woodtick. Call a couple of concrete companies and tell them what you want to do. They'll be able to tell you what type and how much you need. There may be a minimum you have to pay for. Ask if there's a chance to cut the cost if you wait for a time to split a load with someone or they can put your concrete in a truck with a larger delivery. Remember, concrete companies normally only deliver the concrete. If you want someone to build the forms, lay the mesh or reinforcing bar (rebar), etc., you'll have to call a contractor. If you do this compare his cost complete with someone that will do the work and you buy the materials.

You would need 1 1/3 yds of concrete. You should pour it 4" thick which would require 1 3/4 yds.

V = 24*18*(1/2) cu ft Cost = 24*18*(1/2) cu ft * $ 42/cu yard * 1 cu yard/27 cu ft Cost = 24*18*(1/2)*42 / 27 .

2 yards