Professional Concrete Mix Calculator. Concrete calculations require volume in cubic yards. Formula: Cubic Yards equals (Length times Width times Depth in feet) divided by 27. Example 10×12 ft slab 4 inches thick: 10 times 12 times 0.33 equals 39.6 cubic feet divided by 27 equals 1.47 cubic yards, order 1.5 yards. Depth in inches to feet: 4 inches equals 0.33 ft, 6 inches equals 0.5 ft, 8 inches equals 0.67 ft. Costs: Ready-mix concrete 100-150 per cubic yard delivered. Requires minimum order 1-2 yards. Fiber-reinforced adds 5-10 per yard. Colored adds 30-60 per yard. Bagged concrete 4-7 per 80-pound bag yields 0.6 cubic feet, economical only for small projects under 1/2 cubic yard. PSI requirements: 2,500 PSI walkways and patios. 3,000 PSI driveways and garage floors. 3,500 PSI foundations and structural. 4,000-5,000 PSI commercial and industrial. Mix ratio: Standard 3,000 PSI uses 1 part cement, 2 parts sand, 3 parts gravel, 0.5 parts water. Bags: One 94-pound cement bag, 200 pounds sand, 300 pounds gravel, yields 4.5 cubic feet of concrete. Reinforcement critical: Wire mesh 6×6 inch welded, placed mid-thickness, prevents cracking. Rebar 1/2 inch diameter, spaced 18 inches, high-load areas. Fiber mesh added to mix, reduces shrinkage cracks. Expansion joints every 10 feet prevents cracking from thermal movement. Control joints cut 1/4 depth creates planned crack location. Slab preparation: Grade and compact subgrade 95 percent compaction. Gravel base 4-6 inches compacted, improves drainage. Vapor barrier 6 mil plastic under slabs prevents moisture migration. Forms 2×4 or 2×6 lumber staked and leveled. Slope 1/4 inch per foot away from buildings drainage. Example driveway: 12 feet wide, 20 feet long, 4 inches thick. Volume: 12 times 20 times 0.33 equals 79.2 cubic feet equals 2.93 cubic yards. Order 3 yards. Cost: Concrete 400, wire mesh 50, labor 600, total 1,050 or 4.40 per sq ft. Pouring and finishing: Pour in sections manageable size. Spread and screed level with 2×4. Bull float smooth large areas. Edger rounds edges prevents chipping. Groover cuts control joints. Broom finish slip-resistant. Smooth trowel finish for interior. Stamped or stained decorative adds 5-15 per sq ft. Curing essential: Keep moist 7 days for strength development. Mist with water or cover with plastic. Curing compound spray-on sealer easier. Concrete gains 70 percent strength in 7 days, full strength 28 days. Don't drive on driveway for 7 days minimum. Common mistakes: Measuring volume in square feet not cubic yards, off by factor of 27. Not ordering enough, can't stop mid-pour, shortages disaster. Skipping reinforcement causes widespread cracking. Pouring in freezing weather below 40 degrees F, won't cure properly. Not preparing subgrade causes settling and cracking. Overworking surface brings water up, weakens finish. Pro tips: Order 5-10 percent extra for spillage and irregular depth. Have extra wheelbarrows and helpers ready, concrete sets in 90 minutes. Wet tools and forms beforehand easier cleanup. Use aluminum magnesium bull float for smoother finish than wood. Don't add water to concrete in truck, weakens significantly. Pour in coolest part of day in hot weather. Alternative to ready-mix: Concrete mixer rent 75-150 per day, economical for 1-2 yards if time available. Mix on site labor-intensive but flexible timing. Bagged concrete good for small posts, steps under 1/2 yard total. Specialty concrete: Lightweight uses expanded clay aggregate, insulating walls. High early strength fast cure, cold weather. Self-leveling floors, no finishing needed. Porous concrete drainage applications. Stamped imitates stone, brick, tile, decorative 8-18 per sq ft. FAQ: How much concrete do I need? Measure length times width times depth in feet, divide by 27 for cubic yards. Can I pour concrete myself? Small projects yes, large slabs hire professionals, very physically demanding. When can I walk on it? 24-48 hours light foot traffic, 7 days heavy use. How thick should concrete be? 4 inches patios and walkways, 4-6 inches driveways, 6-8 inches heavy vehicles, 12 inches foundations. Does concrete crack? Yes, some cracking normal, control joints minimize, reinforcement prevents spreading.