Concrete Mix Ratio Calculator
Convert concrete mix ratios and calculate exact cement, sand, and aggregate quantities for any volume. Free online concrete mix calculator for M10, M15, M20, M25, and custom mix designs.
Concrete Mix Ratios
Concrete mix ratios define the proportions of cement, sand, and aggregate. Different grades suit different applications. M-grade designations indicate compressive strength in MPa after 28 days of curing.
Mix Ratio Formula
Total Parts = Cement + Sand + Aggregate
Cement Volume = (Ratio Part / Total) × Dry Volume
Dry Volume = Wet Volume × 1.54
Cement Bags = Cement Volume / 0.035 (m³ per bag)
Dry volume is 54% more than wet volume due to voids and shrinkage. One cement bag (50 kg) equals 0.035 cubic meters or 1.25 cubic feet.
Standard Mix Designs
| Grade | Ratio | Strength (MPa) | Common Use |
|---|---|---|---|
| M5 | 1:5:10 | 5 MPa | Mass concrete, foundations |
| M7.5 | 1:4:8 | 7.5 MPa | Footings, floor bases |
| M10 | 1:3:6 | 10 MPa | Paths, non-structural |
| M15 | 1:2:4 | 15 MPa | Residential slabs, walls |
| M20 | 1:1.5:3 | 20 MPa | Beams, columns, slabs |
| M25 | 1:1:2 | 25 MPa | Heavy structures, bridges |
| M30 | Design Mix | 30 MPa | High-rise, prestressed |
Cement Bags Calculation
M15 Mix (1:2:4) per Cubic Meter
Total parts: 1+2+4 = 7
Cement: 1/7 × 1.54 = 0.22 m³
Cement bags: 0.22 / 0.035 = 6.3 bags
Sand: 0.22 × 2 = 0.44 m³
Aggregate: 0.22 × 4 = 0.88 m³
M20 Mix (1:1.5:3) per Cubic Meter
Total parts: 1+1.5+3 = 5.5
Cement: 1/5.5 × 1.54 = 0.28 m³
Cement bags: 0.28 / 0.035 = 8 bags
Sand: 0.28 × 1.5 = 0.42 m³
Aggregate: 0.28 × 3 = 0.84 m³
M25 Mix (1:1:2) per Cubic Meter
Total parts: 1+1+2 = 4
Cement: 1/4 × 1.54 = 0.385 m³
Cement bags: 0.385 / 0.035 = 11 bags
Sand: 0.385 × 1 = 0.385 m³
Aggregate: 0.385 × 2 = 0.77 m³
Material Quantities per 50 kg Bag
| Mix Grade | Concrete Volume | Sand Required | Aggregate Required |
|---|---|---|---|
| M10 (1:3:6) | 0.27 m³ | 0.08 m³ | 0.16 m³ |
| M15 (1:2:4) | 0.16 m³ | 0.07 m³ | 0.14 m³ |
| M20 (1:1.5:3) | 0.125 m³ | 0.053 m³ | 0.105 m³ |
| M25 (1:1:2) | 0.09 m³ | 0.035 m³ | 0.07 m³ |
Water-Cement Ratio
Recommended W/C Ratios
M10: 0.50-0.55
M15: 0.45-0.50
M20: 0.40-0.45
M25: 0.35-0.40
M30+: 0.30-0.35
Water per Bag (50 kg)
W/C 0.40: 20 liters
W/C 0.45: 22.5 liters
W/C 0.50: 25 liters
W/C 0.55: 27.5 liters
Workability Guidelines
Low slump (25-50 mm): Foundations
Medium slump (50-100 mm): Slabs, beams
High slump (100-150 mm): Pumped concrete
Add plasticizers for high workability
Curing Requirements
Minimum curing: 7 days
Recommended: 14 days
Optimal: 28 days
Keep moist, protect from sun and wind
Frequently Asked Questions
What is the best mix ratio for a driveway?
Use M20 (1:1.5:3) or M25 (1:1:2) for driveways. These mixes provide 20-25 MPa strength for vehicle loads. Add fiber reinforcement for crack resistance. Minimum thickness is 4 inches for cars, 6 inches for trucks.
How many cement bags for 1 cubic meter of M20 concrete?
M20 concrete requires approximately 8 bags of 50 kg cement per cubic meter. This equals 400 kg of cement. Sand requirement is 0.42 m³ and aggregate is 0.84 m³.
What does M20 mean in concrete?
M20 indicates 20 MPa (2900 psi) compressive strength after 28 days of curing. The M stands for mix. M20 is standard for residential construction including slabs, beams, and columns.
How much water should I add to concrete mix?
Water-cement ratio should be 0.40-0.50 for most applications. For 50 kg cement, add 20-25 liters of water. Too much water weakens concrete. Too little makes it unworkable.
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