Concrete Cubic Yards Calculator
Slabs, footings, columns, sonotubes, walls, curbs and stairs — bag counts and ready-mix loads, instantly.
Pick a project, enter dimensions in any unit, and get cubic yards, 40 / 60 / 80 lb bag counts, ready-mix truck loads and cost — with a live formula breakdown so you see exactly how the number is built.
Concrete calculator
Pick the project, enter dimensions — get yards, bags, trucks and cost.
$130–$180 / yd³
Waste factor
5% formed slabs · 10% footings & walls · 15% stairs.
How to calculate concrete cubic yards
Live formula breakdown — the math updates as you change project, dimensions and waste.
Apply the volume formula
Each project type has its own equation.
Plug values (in feet)
Inches → feet by ÷ 12; meters → feet by × 3.281.
Cubic feet
Multiply through to get raw volume.
Convert ft³ → yd³ (÷ 27)
1 yd³ = 27 ft³.
Add waste
5–15% extra to cover spillage and over-dig.
Total to order
Multiply by density (4,050 lb/yd³) for weight, or by bag yield for bag count.
How many bags of concrete do I need?
Bag math at a glance, plus the rule of thumb for switching to ready-mix.
Easiest to lift. Small repairs and post-holes.
Sweet spot for DIY. Manageable weight.
Best cost per yard. Heavy — get help.
Recommended thickness and PSI strength
Pick the strength and thickness that match your use case. Higher PSI = more cement = more cost.
The 1 : 2 : 3 DIY mix ratio
For small pours where ready-mix doesn't make sense. Yields ≈ 3,000 PSI when cured properly.
Add water until workable — roughly 0.5 parts by volume. Don't over-water (weak concrete).
Need to size the components? Use the sand calculator and the gravel calculator.
8 project types in one calculator
Each shape uses its own formula. Tap to load it in the calculator above.
6 worked concrete examples
Common jobs with the actual math.
Patio slab 10 ft × 12 ft × 4 in
Backyard patio with light foot traffic.
Garage slab 24 ft × 24 ft × 6 in
Two-car garage with rebar grid.
Sonotube 12 in dia × 4 ft deep
Single deck footing pour.
Sidewalk 30 ft × 3 ft × 4 in
Front-yard walkway.
3 exterior stairs, 36 in wide
7-in rise, 11-in run, porch steps.
Foundation wall 8 ft × 24 ft × 8 in
Basement perimeter wall.
Ready-mix truck sizes and short-load fees
Three useful drum sizes. Pick before you pour — short-load fees apply on small orders.
Fits a residential driveway. Best for 1–3 yd³ pours. No short-load fee.
Full-size truck. Short-load fee $60–$150 per yard under ~8 yd³.
Largest tridem drum. Commercial pours only.
Concrete calculator FAQs
The 12 most-asked questions about pouring and ordering concrete.
How many 80 lb bags of concrete in a cubic yard?
45 bags. Each 80 lb bag yields about 0.60 cubic feet of cured concrete (27 ÷ 0.60 = 45).
How many 60 lb bags of concrete equal 1 cubic yard?
60 bags. Each 60 lb bag yields about 0.45 cubic feet.
How many 40 lb bags in a cubic yard?
90 bags. Each 40 lb bag yields about 0.30 cubic feet.
When should I use ready-mix vs bagged concrete?
Under 1 yd³ bags win on cost and convenience. 1–2 yd³ is borderline (short-load fee $60–$150 applies). Above 2 yd³ ready-mix is always cheaper.
What PSI concrete do I need?
2,500 PSI for interior, 3,000 PSI for residential patios, 3,500–4,000 PSI for driveways, 4,500+ PSI for structural footings and columns.
How thick should a concrete patio be?
4 inches for residential patios. Driveways use 4–6 inches with rebar or wire mesh reinforcement.
What is the minimum ready-mix order?
Most suppliers have a 1 yd³ minimum with a short-load fee of $60–$150 per yard short of a full 10 yd³ truck.
How much does a cubic yard of concrete weigh?
About 4,050 lbs (≈ 2.03 short tons) for standard 3,000 PSI ready-mix.
DIY mix ratio for concrete?
1 part cement, 2 parts sand, 3 parts gravel — the classic 1:2:3 mix. Add water until workable (≈ 0.5 parts).
How long does concrete take to cure?
24 hours to safely walk on, 7 days for light loads, 28 days for full design strength. Keep moist for the first 7 days.
How much waste should I add?
5% for slabs in formed areas, 10% for footings and walls (over-dig), 15% for stairs and complex geometry.
Do I need rebar in a concrete patio?
Wire mesh is sufficient for most patios. Use #4 rebar on 16–18 in grid for driveways or any slab carrying vehicles.
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