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Concrete Mix Calculator — Get the Right Ratio

Enter your concrete volume and select a mix ratio to instantly calculate bags of cement, cubic feet of sand and gravel, and gallons of water. Free, no signup.

Concrete Mix Calculator

Enter volume and choose a mix ratio to get cement bags, sand, gravel, and water

Enter a volume above to see your mix material quantities

Standard Concrete Mix Ratios

The table below shows the three most common concrete mix ratios, their intended use cases, and approximate cement content per cubic yard of finished concrete:

RatioUse CaseCement bags/yd³Notes
1:2:3Slabs, driveways, sidewalks5.5General purpose, ~3,000 psi
1:1.5:2.5Columns, beams, footings7.0High strength, ~4,500 psi
1:3:6Mass fill, blinding layers4.0Lean mix, economy grade

How to Mix Concrete

Follow these steps to mix concrete by hand or with a portable mixer:

  1. Measure materials accurately. Use a bucket or measuring box to portion cement, sand, and gravel in the correct ratio. Consistent proportions are the single biggest factor in achieving target strength.
  2. Combine dry ingredients first. Mix cement, sand, and gravel together until the color is uniform throughout with no visible streaks of individual materials.
  3. Add water gradually. Start with about 80 percent of the required water and mix thoroughly before deciding whether to add more. The target consistency is a stiff but workable paste that holds its shape without slumping.
  4. Mix for at least 3 minutes. Continue mixing after adding all water until the mix is homogeneous and no dry pockets remain at the bottom of the mixer or trough.
  5. Place and consolidate immediately. Fresh concrete loses workability quickly. Place within 30 to 45 minutes of mixing, and use a vibrator or rodding to remove air pockets and ensure proper consolidation around reinforcement.
  6. Cure for at least 7 days. Keep the surface moist or covered with plastic sheeting to prevent rapid moisture loss. Proper curing significantly increases final strength and reduces surface cracking.

Concrete Mix Design Tips

The water-to-cement ratio is the most critical variable in concrete mix design. Lowering the w/c ratio below 0.50 increases compressive strength and reduces permeability, which matters for durability in freeze-thaw conditions or exposure to deicing salts. If you need a lower w/c ratio without sacrificing workability, use a water-reducing admixture (plasticizer) rather than simply adding more water. Modern superplasticizers can reduce water demand by 15 to 25 percent while maintaining the same slump.

Aggregate quality has a significant impact on the final product. Well-graded aggregate with a mix of particle sizes packs more efficiently, reducing the cement paste needed to fill voids and lowering overall cost. Clean aggregate free of clay, silt, and organic matter is essential: even a small amount of fine contaminants can reduce bond between aggregate and cement paste, weakening the concrete well below its design strength.

For outdoor flatwork, consider adding air-entraining admixtures to improve resistance to freeze-thaw cycles. Entrained air (4 to 6 percent by volume) creates microscopic bubbles that relieve hydraulic pressure when water freezes in the concrete pores. This significantly extends the service life of driveways, sidewalks, and patios in cold climates. Air entrainment does slightly reduce compressive strength, so increase cement content by one bag per cubic yard to compensate when specifying air-entrained concrete.

Frequently Asked Questions

What is the standard concrete mix ratio?
The most common general-purpose mix ratio is 1:2:3 — one part cement, two parts sand, and three parts coarse aggregate (gravel) by volume. This mix produces concrete with a compressive strength of around 3,000 to 3,500 psi after 28 days of curing, which is sufficient for driveways, sidewalks, patios, and most residential slabs. Higher-strength applications such as structural columns and bridge decks use leaner cement ratios like 1:1.5:2.5, which yields around 4,000 to 5,000 psi.
How many bags of cement do I need per cubic yard?
For a standard 1:2:3 mix, you need approximately 5.5 bags of 94-pound Portland cement per cubic yard of concrete. A high-strength 1:1.5:2.5 mix requires about 7 bags per cubic yard due to the higher cement content. A lean 1:3:6 mix uses roughly 4 bags per cubic yard and is typically used for mass fill or non-structural concrete where economy is more important than strength. The calculator above shows the exact bag count for your chosen volume and ratio.
How much sand and gravel do I need per cubic yard of concrete?
For a 1:2:3 mix, one cubic yard of concrete requires approximately 14.9 cubic feet of sand and 22.4 cubic feet of gravel. Note that the combined dry volume of the ingredients is greater than 27 cubic feet because cement paste fills voids between aggregate particles, reducing total volume. For a high-strength 1:1.5:2.5 mix, use about 12.6 cubic feet of sand and 21.0 cubic feet of gravel per cubic yard. Always order 10 percent extra to account for spillage and waste.
How much water do I add to a concrete mix?
A general rule of thumb is to use approximately 24 gallons (about 200 pounds) of water per cubic yard of concrete for a standard mix. The water-to-cement ratio (w/c ratio) is the key quality metric: a w/c ratio of 0.45 to 0.55 is typical for general work, while structural concrete often targets 0.40 or lower for higher strength and durability. Adding too much water weakens the concrete and increases shrinkage cracking. In hot or dry conditions, use cooler water and consider admixtures to maintain workability without raising the w/c ratio.
What is the difference between a 1:2:3 and 1:1.5:2.5 mix?
Both ratios produce structural-grade concrete, but the 1:1.5:2.5 mix contains more cement relative to aggregate, resulting in higher compressive strength (typically 4,000 to 5,000 psi vs. 3,000 to 3,500 psi for 1:2:3). The high-strength mix is used for structural beams, columns, footings, and other load-critical applications. It costs more in cement but requires less volume for the same load capacity. The 1:2:3 mix is the standard choice for flatwork such as slabs, driveways, and sidewalks where 3,000 psi is sufficient.
Can I use a custom mix ratio in this calculator?
Yes. Select the "Custom ratio" option and enter your cement, sand, and gravel parts in the fields that appear. The calculator derives the material quantities proportionally based on approximately 56 cubic feet of total dry materials per cubic yard of finished concrete. Custom ratios are useful for specialty mixes, site-specific aggregate types, or when following a structural engineer's mix design. Make sure all three parts are greater than zero — the calculator will show an error if any part is missing.

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