How Much Concrete Do You Need? Concrete Volume Calculator
How much concrete do you need?
Concrete Calculator
How Much Concrete Do You Need?
Calculate cubic yards, bags, and cost for slabs, footings, columns, and steps.
Min 4" patios · 6" driveways
Recommend 5–10%
Typical: $110–$175/yd³
Results are for informational purposes only.
Related Calculators
Time ROI Calculator
What is the return on investment of your time?
Time Duration Calculator
How long between these two dates or times?
Productivity Score
How productive are you — really?
Sales Tax Calculator
What will this purchase cost after tax?
Dice Roller
What number will you roll?
Meeting Cost Calculator
How much are your meetings actually costing your organization?
Get this result by email
We'll send you this summary so you can revisit it anytime — useful when making a final decision.
🔒 We'll only send your result. No spam, no noise.
Ordering the right amount of concrete is critical for any construction project — order too little and your pour is interrupted, order too much and you're paying for waste. Concrete is typically ordered by the cubic yard (27 cubic feet) from ready-mix suppliers, or in pre-mixed bags for smaller projects. Getting the volume right before ordering saves time, money, and the logistical nightmare of a mid-pour shortage. The calculation varies by shape. For slabs and footings: Volume = Length × Width × Thickness. For circular slabs or columns: Volume = π × radius² × depth. For steps: each step is calculated as a rectangular volume, then summed. All dimensions must be in consistent units before calculating, and the result is converted to cubic yards by dividing by 27 (since 1 cubic yard = 27 cubic feet). A critical professional practice: always add 5–10% to your calculated volume for waste, spillage, and uneven forms. Concrete is difficult to work with when running short — small pours take time to set, and adding fresh concrete to partially-set concrete creates weak joints. This calculator includes the waste factor in its recommendations. Pre-mixed bags are practical for small jobs: 60 lb bags yield 0.45 cubic feet, 80 lb bags yield 0.60 cubic feet. This calculator shows how many bags you'd need, though ready-mix is more economical for anything over 0.5 cubic yards.
- →Planning a concrete slab for a patio, driveway, garage floor, or shed foundation
- →Calculating concrete for footings, piers, or columns for a deck or structure
- →Estimating bags of concrete needed for small projects like fence posts or steps
- →Checking your concrete order before calling a ready-mix supplier
- →Estimating project cost before getting formal quotes
Jason is pouring a 20' × 12' patio at 4" depth. Volume: 20 × 12 × (4/12) = 80 cubic feet = 2.96 cubic yards. With 10% waste: 3.26 cubic yards — round up to 3.5 cubic yards order. In 80-lb bags: 3.26 × 27 / 0.6 = 147 bags (not practical — he'll call for ready-mix). Estimated cost at $140/yard: $490 for the concrete order.
How many 80 lb bags of concrete equal one cubic yard?
One 80-lb bag yields approximately 0.60 cubic feet. One cubic yard = 27 cubic feet, so you need about 45 bags (27 ÷ 0.60 = 45) per cubic yard. For 60-lb bags: 60 bags per yard (27 ÷ 0.45). Pre-mixed bags become expensive for anything over about 0.5 cubic yards — ready-mix is more economical for larger pours.
How thick should a concrete slab be?
For foot traffic only (patios, walkways): 4 inches minimum. For vehicle traffic (driveways): 6 inches minimum, 8 inches for heavy vehicles. Garage floors: 4–6 inches. Structural slabs with rebar: consult an engineer. Footings: width typically 2× foundation width, depth to below frost line (varies by climate — up to 48 inches in cold climates).
What is the typical price of ready-mix concrete?
Ready-mix concrete prices vary by region and market conditions, typically ranging from $110–$175 per cubic yard. Short loads (under 5 yards) often incur an additional short-load fee of $50–$150. There may also be Saturday/overtime delivery charges and fuel surcharges. Get quotes from multiple suppliers and ask about short-load minimums.
How long does it take for concrete to cure?
Concrete gains strength continuously over time. It reaches approximately 70% of its 28-day strength in the first 7 days. It can bear foot traffic after 24–48 hours, vehicle traffic after 7 days, and full heavy-load capacity after 28 days. Keep it moist (cure it) for at least 7 days by covering with plastic sheeting or applying a curing compound.