🏗️ Concrete Calculator PRO
Volume, rebar, formwork, material breakdown & cost — all in one.
Dimension Diagram — updates as you type
Slab plan view. Length × width gives the area; thickness gives the depth of the pour.
1 Project Type
2 Shape
3 Dimensions
4 Rebar (Optional)
5 Options
Labour Cost
Results
Volume
Bags Needed
Material Breakdown (approximate)
Rebar
Formwork
Cure Time
⚠️ Pre-Export Checklist
- Footings measured on-site
- Sub-grade compacted and level
- Reinforcement placed per structural drawings
- Formwork secured and oiled
- Building permit obtained
- Weather forecast checked (no rain for 24h)
- Pump truck / wheelbarrows arranged
Professional Concrete Estimation Guide
Show formulas, worked examples & pro tips ▼
Formulas
Rectangle = L × W × T
L-Shape = (L₁ × W₁) − (L₂ × W₂) × T
Trapezoid= ((Top + Bottom) ÷ 2) × Length × T
Circle= π × r² × Depth × Quantity
Stairs= Number of steps × (Riser × Tread × Width)
Material Mix (1:2:3 ratio):
Cement = Volume ÷ (1+2+3) × 1.5 (bags per cu ft)
Sand = Volume × (2 ÷ 6) × 1.5 tons per cu yd
Gravel = Volume × (3 ÷ 6) × 1.5 tons per cu yd
Rebar Weight= Bars × Length × Weight per ft (varies by bar size)
Worked Example — 10×10 ft Slab, 4" thick
- Volume: 10 × 10 × (4÷12) = 33.3 cu ft = 1.23 cu yd
- Bags (80 lb): 33.3 ÷ 0.60 = 56 bags → with 10% waste = 62 bags
- Cement: ~62 bags × 94 lb = 2.9 tons cement
- Sand: ~1.1 cu yd = 1.6 tons
- Gravel: ~1.6 cu yd = 2.4 tons
- Water: ~33.3 × 6 gal/cu yd = 25 gallons
- Rebar (#4 @ 12" O.C. both ways): 11 bars × 10 ft = 110 ft = 73.5 lb
Common Mistakes to Avoid
- Forgetting to convert inches to feet (4 in = 0.333 ft, not 4)
- Not adding waste — always 5-15% depending on site conditions
- Using wrong bag yield — 80 lb = 0.6 cu ft, 60 lb = 0.45, 40 lb = 0.30
- Ignoring rebar overlap — add 40× bar diameter for each splice
- Not checking concrete pump accessibility for large pours
- Pouring in direct sunlight without curing compound
Pro Tips
- For pours >1 cu yd, order ready-mix trucks instead of bags
- Use a concrete vibrator to eliminate air pockets
- In hot weather (>90°F), add ice to mix water to slow setting
- Spray curing compound immediately after finishing
- Control joints should be spaced at 24-30× slab thickness
- Order 10% extra — uneven subgrade always uses more concrete
Drag to rotate — Scroll to zoom
حاسبات مرتبطة
Frequently used together on the same project.
Client & Quote (prints on PDF & Excel)
Adjustments (applies to exports)
Contingency is added as a separate line on the exported cost summary. Waste % is printed as an advisory reminder.
Project notes (prints on PDF & Excel)
Result compare (A/B)
| Item | Pinned | Current | Change |
|---|---|---|---|
Saved rates auto-apply from your Price Library. Advanced details stay in your browser — nothing is uploaded except inside your own PDF/Excel exports.
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✅Method, Sources & Review
Maintained by theBuildingCalc methods desk· Last reviewedSeptember 23, 2026. This calculator implements the standards and references below; every figure can be rechecked against the formulas and worked example on this page.
Results are estimates, not engineering advice. Verify against local codes and licensed professionals for structural, electrical, and gas work. See ourTerms. Spotted an error? Report it— corrections ship with the next review.