Concrete calculator
Geometric cubic yards for slabs, strip footings, round columns (sonotubes), walls, solid stairs, ramps, round slabs or ring footings. Pick the shape above; quantity estimation — structural sizing is signed by a qualified professional.
Purchase quantity
4.199 yd³
Net measurement: 3.924 yd³ · Waste 7 %
- Net concrete3.924 yd³
- Concrete to order (with waste)4.199 yd³
Ready-mix or bags? At this volume: ready-mix truck.
Your prices per language/currency. Used when you enable “Use my prices” in calculators. My prices →
How it's calculated (visible formula)
slab V_ft³=l_ft×w_ft×t_ft ÷ 27 = yd³; column V=πr²h; stairs V=n×(tread×riser/2)×w; ramp V=(l×h/2)×w; round V=πr²×t; ring V=π(R²−r²)×h; order = V×(1+waste)
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
Ready-mix or bags? (guide)
| Volume | Recommendation |
|---|---|
| Under 0.5 yd³ (~22 bags) | Bags (mix on site) |
| 0.5–1 yd³ (22–45 bags) | Bags; price a short load to compare |
| 1–2 yd³ | Price both: bags vs short-load ready-mix |
| Over 2 yd³ | Ready-mix truck (order extra; pump if needed) |
Worked example: 13×10 ft slab, 6 in thick
- V = 13×10×0.5 ft = 65 ft³ = 2.4 yd³
- +7% → 2.6 yd³
→ Order 2.75–3 yd³ from the plant (round up).
Common mistakes
- Ordering exact m³ with no plant margin.
- Forgetting pumping, formwork and rebar.
- Mixing m³ with m².
From calculation to quote
Add labor, overhead and your margin, and generate the professional PDF.
FAQs
- Ready-mix or site-mixed?
- Above ~1–2 m³ ready-mix usually pays off in consistency; this page estimates volume either way.
- How much concrete for a slab?
- Length × width × thickness. A 13×10 ft slab at 6 in is ≈2.4 yd³ net: order 2.75–3 yd³.
- How do I calculate cubic yards?
- By shape: slab, footing, column (πr²h) or wall. Pick the shape above; waste is added automatically.
- How much cement, sand and gravel per cubic yard?
- At the reference dosage of 300 kg cement per m³ (≈510 lb/yd³): 12 × 25 kg bags, 0.6 m³ sand and 0.7 m³ gravel per m³. Full breakdown in the cement calculator.
- How many 80 lb bags in a cubic yard?
- An 80 lb bag yields ~0.6 ft³: a cubic yard (~27 ft³) needs about 45 bags. That's why above ~1 yd³ it's worth pricing ready-mix.
- How much waste for concrete?
- 7% by default: it covers spillage and rounding to a plant order.
- Rebar included?
- No: this calculator only cubes concrete.
- How many cubic yards for a 5×4 m slab, 15 cm thick?
- That's 3 m³ ≈ 3.9 yd³ net, ≈4.2 yd³ with 7% waste. Switch to Imperial to enter feet and inches and get cubic yards directly.
- Does it handle footings, columns and walls?
- Yes — choose the shape above: strip footing (length × width × depth), round column by diameter and height (e.g. sonotubes), wall by length × height × thickness, or stairs by steps, tread, riser and width.
- How do I cube a concrete staircase?
- Each step counts as a triangular prism (tread × riser ÷ 2) times width, times the number of steps. Example: 10 steps of 11×7 in and 3 ft wide ≈ 8 ft³ net (≈0.3 yd³). Landings and stringers are cubed separately.
- How do I compare bags vs ready-mix on cost?
- Multiply your bags (about 45 × 80 lb per yd³) by your bag price and compare against the plant's short-load price plus delivery fee. With no real prices there's no valid comparison — save yours in My prices.
- Does it handle ramps?
- Yes — choose “Ramp” above and enter length, rise and width: it cubes the triangular wedge (length × rise ÷ 2). Side walls are cubed separately.
- What about a round patio slab?
- Yes — choose “Round slab” and enter diameter and thickness: it cubes the cylinder (πr²). Example: a 10 ft patio at 6 in thick is ≈39.3 ft³ (≈1.45 yd³) net — order 1.75 yd³ with waste.
- How do I cube a ring footing?
- Choose “Ring footing” and enter outside diameter, inside diameter and height: it cubes the annulus π(R²−r²). The inside must be smaller than the outside; rebar follows the design.
- Does it handle trench footings?
- Yes — a trench footing is a strip footing: choose “Footing” and enter length × width × depth. Blinding concrete, if any, goes as a separate line.
- How many 60 lb or 40 lb bags make a yard?
- About 60 × 60 lb bags or 90 × 40 lb bags per cubic yard (a 60 lb bag yields ~0.45 ft³, a 40 lb bag ~0.3 ft³). Above ~1 yd³ price ready-mix against bags.
- Quikrete or Sakrete — which bag should I buy?
- Yield per weight is the same (80 lb ≈ 0.6 ft³ for either brand): buy on store price and availability, and confirm the yield on your bag's data sheet.
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.