Concrete Mix Calculator
Calculate mix ratios and material quantities for concrete projects
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General purpose mix for most residential projects
Standard: 4" patios, 6" driveways
94lb bag Portland cement
80lb bag pre-mixed concrete
Quick Answer
The standard concrete mix ratio is 1:2:3 (1 part cement, 2 parts sand, 3 parts gravel) with a water-cement ratio of 0.5. One 80-pound bag of pre-mixed concrete yields 0.6 cubic feet. For a 10' × 10' × 4" slab, you need approximately 1.25 cubic yards or about56 bags of 80lb concrete mix.
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Concrete Mix Ratios Explained
| Mix Type | Ratio (C:S:G) | Strength |
|---|---|---|
| Standard | 1:2:3 | 2,500-3,000 PSI |
| High-Strength | 1:1.5:2.5 | 4,000-5,000 PSI |
| Fast-Setting | 1:2:2.5 | 3,000-4,000 PSI |
| Lean Mix | 1:3:6 | 1,500-2,000 PSI |
| Rich Mix | 1:1:2 | 5,000+ PSI |
Understanding Mix Ratios
A 1:2:3 ratio means 1 part cement to 2 parts sand to 3 parts gravel by volume. More cement = stronger concrete but more expensive. The standard 1:2:3 mix is ideal for most DIY projects and provides a good balance of strength, workability, and cost.
Concrete Strength (PSI) Guide
2,500 PSI
Light-duty residential
- • Sidewalks
- • Patios
- • Interior slabs
- • Non-traffic areas
3,000 PSI
Standard residential
- • Driveways
- • Garage floors
- • Foundations
- • Footings
3,500 PSI
Heavy residential
- • Foundation walls
- • Structural footings
- • RV parking
- • Heavy equipment
4,000 PSI
Commercial grade
- • Commercial floors
- • Parking garages
- • Structural columns
- • Bridge decks
4,500+ PSI
Heavy commercial/industrial
- • Industrial floors
- • Heavy traffic
- • Precast concrete
- • High-rise structures
6,000+ PSI
Specialty applications
- • High-performance
- • Post-tensioned
- • High-rise columns
- • Infrastructure
Mixing Methods Compared
Pre-Mixed Bags
Convenient all-in-one bags with cement, sand, and gravel already mixed.
- ✓ Easy to use
- ✓ Consistent quality
- ✓ Best for small projects
- ✗ More expensive per yard
- ✗ Heavy to handle
Best for: Under 1 cubic yard
Mix From Scratch
Buy separate ingredients and mix yourself.
- ✓ Most economical
- ✓ Custom mix ratios
- ✓ Control over quality
- ✗ More labor intensive
- ✗ Requires knowledge
Best for: 1-3 cubic yards
Ready-Mix Delivery
Professional concrete delivered by truck.
- ✓ Perfect consistency
- ✓ Least labor
- ✓ Fast for large pours
- ✗ Minimum order (usually 1 yd)
- ✗ Limited working time
Best for: Over 1 cubic yard
Water-Cement Ratio
The water-cement ratio is crucial for concrete strength and durability. It's the weight of water divided by the weight of cement. Less water = stronger concrete, but harder to work with.
Recommended Ratios
| 0.35-0.40 | High-strength (5,000+ PSI) |
| 0.45 | Standard (3,500-4,000 PSI) |
| 0.50 | Residential (3,000 PSI) |
| 0.55-0.60 | General purpose (2,500 PSI) |
Water Per Bag of Cement
- • 94lb bag: 4-6 gallons (0.4-0.6 ratio)
- • Add water gradually
- • Stop when mix holds shape
- • Should not be soupy
- • Should not crumble
Pro Tip: The Slump Test
Fill a cone with concrete, lift it off, and measure how much it "slumps." For most projects, aim for 4-6 inches of slump. Less slump = stiffer mix = stronger concrete. More slump = easier to work but weaker.
Curing Concrete Properly
Proper curing is essential for concrete to reach its full strength. Concrete that dries out too quickly will be weak and prone to cracking.
Curing Timeline
- 24 hours:Initial set - don't walk on it
- 48 hours:Can walk on carefully
- 7 days:70% strength - light use OK
- 14 days:85% strength
- 28 days:Design strength reached
Curing Methods
- 1.Water curing: Spray/mist 2-3 times daily for 7 days
- 2.Plastic sheet: Cover to retain moisture
- 3.Curing compound: Spray-on sealer
- 4.Wet burlap: For vertical surfaces
- 5.Ponding: For flat slabs (flood with water)
Frequently Asked Questions
What is the standard concrete mix ratio?
The standard concrete mix ratio is 1:2:3 (1 part cement, 2 parts sand, 3 parts gravel) with a water-cement ratio of 0.5. This produces concrete with approximately 2,500-3,000 PSI strength, suitable for most residential projects like sidewalks, patios, and driveways. For stronger concrete, increase the cement proportion.
How much water do I add to concrete mix?
The water-cement ratio should be between 0.4 and 0.6 by weight. For every 94 pounds (1 bag) of cement, use 4-6 gallons of water. Less water creates stronger concrete but is harder to work with. Add water gradually while mixing until you achieve a workable consistency that holds its shape but isn't crumbly.
What is the strongest concrete mix ratio?
A high-strength concrete mix ratio is 1:1.5:2.5 (cement:sand:gravel) with a low water-cement ratio of 0.35-0.4. This produces concrete with 4,000-5,000+ PSI strength. For even stronger concrete (6,000+ PSI), reduce water further and consider adding admixtures, silica fume, or other supplementary cementitious materials.
How many bags of concrete do I need?
An 80-pound bag of pre-mixed concrete yields about 0.6 cubic feet. For 1 cubic yard (27 cubic feet), you need approximately 45 bags of 80lb concrete or 60 bags of 60lb concrete. For a 10ft × 10ft × 4inch slab (33.3 cu ft or 1.23 cu yd), you'd need about 56 bags of 80lb mix.
What is the difference between concrete and cement?
Cement is just one ingredient in concrete. Cement is a fine gray powder made from limestone and clay that acts as a binder. Concrete is the final product made by mixing cement with sand (fine aggregate), gravel (coarse aggregate), and water. The cement chemically reacts with water (hydration) to bind the aggregates together into a hard, stone-like material.
Can I mix concrete by hand?
Yes, you can mix concrete by hand for small projects (under 1/4 cubic yard or about 7 cubic feet). Use a wheelbarrow, mixing tub, or on a clean concrete surface. Combine dry ingredients first, create a crater in the center, then add water gradually while mixing. For larger projects, rent a concrete mixer or order ready-mix delivery.
How long does concrete take to cure?
Concrete sets initially in 24-48 hours and reaches about 70% of its design strength in 7 days. Full strength (design strength) is achieved at 28 days, though concrete continues to strengthen over months and years. Keep concrete moist during the first 7 days. Avoid heavy loads for at least 7 days and full structural loads for 28 days.
What PSI concrete do I need?
2,500 PSI: Residential sidewalks, patios, non-traffic areas. 3,000 PSI: Driveways, garage floors, residential foundations. 3,500 PSI: Foundation walls, footings, structural applications. 4,000 PSI: Commercial floors, parking structures. 4,500+ PSI: Heavy traffic, industrial, and specialized applications. Most residential projects use 2,500-3,500 PSI.
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Dr. Snezana Lawrence
Mathematical Historian | PhD from Yale
Dr. Lawrence is a published mathematical historian with a PhD from Yale University. She ensures mathematical precision and accuracy in all our calculations, conversions, and academic score calculators. Her expertise spans computational mathematics and educational assessment.
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