A concrete mix calculator determines the exact amounts of Portland cement, sand, gravel, and water needed for a custom concrete mix. Standard mixes are defined by a cement:sand:gravel volume ratio — for example, 1:2:3 produces 3,500 PSI concrete suitable for driveways and slabs. Mixing from scratch lets you dial in the exact PSI strength and is more economical than pre-mixed bags for pours over one cubic yard.
Concrete Mix Designer
Select Concrete Strength
— or choose by application
Enter Custom Mix Ratio (by volume)
Total Volume Needed
Mix Breakdown
Standard Mix Ratio Reference
| Mix Type | Ratio (C:S:G) | Target PSI | W/C Ratio | Best For |
|---|---|---|---|---|
| Lean | 1 : 3 : 6 | 2,000 | 0.6 | Mass fill, non-structural |
| Standard Lean | 1 : 3 : 5 | 2,500 | 0.55 | Walkways, light slabs |
| Standard | 1 : 2.5 : 4 | 3,000 | 0.5 | Sidewalks, patios, slabs |
| General Purpose | 1 : 2 : 3 | 3,500 | 0.5 | Driveways, garage slabs |
| Rich | 1 : 1.5 : 3 | 4,000 | 0.45 | Footings, columns, foundations |
| Very Rich | 1 : 1 : 2 | 4,500+ | 0.40 | Structural columns, heavy loads |
How to Use the Concrete Mix Calculator
Mixing your own concrete from Portland cement, sand, and gravel is more economical than pre-mixed bags for pours over one cubic yard — and gives you precise control over strength and workability. This concrete mix calculator tells you exactly how many bags of cement, cubic feet of sand and gravel, and gallons of water you need for any mix ratio and volume. It eliminates the guesswork and trips back to the hardware store.
Step 1: Choose Your Mix Strength
Select a PSI strength preset or switch to Custom Ratio mode. The four PSI presets cover the most common residential and light commercial applications: 2,500 PSI for sidewalks and fill work, 3,000 PSI for patios and slabs, 3,500 PSI for driveways and garage floors, and 4,000 PSI for footings and structural columns. You can also click an application button (Sidewalk, Slab, Driveway, Footing) to automatically select the appropriate mix. In Custom Ratio mode, enter the exact cement:sand:gravel proportions and water-to-cement ratio for specialty mixes.
Step 2: Enter Your Total Volume
Enter the total volume of concrete you need in cubic feet or cubic yards. If you already know your slab dimensions, use our Concrete Calculator first to determine your cubic yard requirement, then bring that number here to design the mix. For reference: 1 cubic yard equals 27 cubic feet. A 10×10 ft slab at 4 inches thick requires about 1.23 cubic yards (33.3 cubic feet). Always add a 5–10% waste factor by increasing your volume input accordingly.
Step 3: Review Cement, Sand, and Gravel Quantities
The results show the number of 94-pound bags of Portland cement, cubic feet of sand, cubic feet of gravel, and gallons of water required for your project. These quantities account for the yield factor — when you combine dry cement, sand, and gravel, the cement particles fill the voids between aggregate particles, so the combined dry volume yields only about 67% of its original volume as wet concrete. This is why you cannot simply add up your raw ingredient volumes and expect to get the right amount of concrete.
Step 4: Understand the Water-to-Cement Ratio
The water-to-cement (w/c) ratio is critical to concrete strength. A ratio of 0.5 means you use 0.5 pounds of water per pound of cement — or about 5 gallons per 94-pound bag. Lower ratios (0.40–0.45) produce stronger concrete but are harder to mix. Higher ratios (0.55–0.60) make mixing easier but significantly reduce final strength. Never add extra water at the job site just to improve workability — use a plasticizer (water reducer) instead if the mix is too stiff.
Step 5: Order Your Materials
Take the cubic feet of sand and gravel to your supplier to convert to tons (1 cubic foot of sand weighs approximately 100 lbs; gravel weighs approximately 105 lbs). Portland cement bags are sold in 94-pound bags at masonry supply stores and most hardware stores. Mix ingredients in a drum mixer for best results: add half the water first, then cement, then sand, then gravel, then add remaining water slowly. Concrete should be poured and finished within 90 minutes of mixing.
FAQ
Is this concrete mix calculator free to use?
Yes, this concrete mix calculator is completely free with no signup required, no paywalls, and no limits. All calculations run entirely in your browser — your project data is never sent to any server and stays private on your device.
Is my data private when I use this tool?
Absolutely. Every calculation runs locally in your browser using client-side JavaScript. No measurements, mix ratios, or personal information are ever transmitted to a server. Your data stays entirely on your device.
What is a 1:2:3 concrete mix ratio?
A 1:2:3 mix ratio means 1 part Portland cement, 2 parts sand, and 3 parts gravel by volume. This produces approximately 3,500 PSI concrete — a general-purpose mix suitable for driveways, patios, slabs, and most structural applications. It uses a water-to-cement ratio of about 0.5, meaning 0.5 gallons of water per pound of cement.
How many bags of cement do I need per cubic yard?
A standard 1:2:3 mix (3,500 PSI) requires approximately 5.2 bags of 94-pound Portland cement per cubic yard of concrete. Richer mixes like 1:1.5:3 (4,000 PSI) require about 6.5 bags per cubic yard, while lean mixes like 1:3:5 (2,500 PSI) need around 3.8 bags per cubic yard. This calculator shows the exact bag count for any mix and volume.
What PSI concrete should I use for a driveway vs. a footing?
Residential driveways and garage slabs typically require 3,000–3,500 PSI (a 1:2.5:4 or 1:2:3 mix). Sidewalks and patios can use 2,500–3,000 PSI. Footings, foundations, and columns that bear structural loads should use 3,500–4,000 PSI (a 1:2:3 or 1:1.5:3 mix). Always check your local building code for minimum strength requirements.
What is the water-to-cement ratio and why does it matter?
The water-to-cement (w/c) ratio is the weight of water divided by the weight of cement. A lower ratio (0.4–0.45) produces stronger, more durable concrete. A higher ratio (0.5–0.6) makes the mix easier to work but reduces strength. The standard rule of thumb is 0.5, meaning 5 gallons of water per 94-pound bag of cement. Never add extra water to make mixing easier — it weakens the final product.
Can I mix my own concrete instead of buying pre-mixed bags?
Yes. Mixing your own concrete from Portland cement, sand, and gravel is often more economical for large pours (over 1 cubic yard) and lets you control the exact mix design and PSI. Pre-mixed bags like Quikrete are convenient for small repairs and posts but cost significantly more per cubic yard. This calculator gives you the exact quantities to buy each ingredient separately.
What is a lean mix vs. a rich mix?
A lean mix has a higher proportion of aggregate (sand and gravel) relative to cement, producing lower-strength, less expensive concrete — typically 2,000–2,500 PSI. Common lean mixes are 1:3:6 or 1:4:8. A rich mix has more cement relative to aggregate, producing high-strength concrete — typically 4,000+ PSI. Common rich mixes are 1:1.5:3 or 1:1:2. Richer mixes cost more but are required for structural elements.