Concrete Mix Ratio Chart by PSI (2026 Guide)

The classic concrete mix ratio is 1:2:3, meaning 1 part cement, 2 parts sand and 3 parts coarse aggregate by volume, which makes roughly 3000 psi concrete for slabs, footings and driveways. The dry proportions set the basic strength, but the water-cement ratio decides the real result. Here is the ratio chart by strength, the water rule that matters most, and how to turn a ratio into bags once you know your volume.

What a concrete mix ratio means

A concrete mix ratio is the proportion of cement, fine aggregate (sand) and coarse aggregate (gravel or crushed stone), always written in that order. A 1:2:3 ratio means one part cement, two parts sand and three parts stone, measured by volume rather than weight.

Cement is the binder that glues everything together. Sand fills the gaps between the larger stones, and the coarse aggregate gives the mix its bulk and strength. Water then triggers the chemical reaction, called hydration, that hardens the paste.

A higher proportion of cement gives higher strength, while a higher proportion of aggregate gives a leaner, lower strength and cheaper mix. Getting these mix proportions right is the heart of correct concrete mixing for any of your concrete projects.

Concrete mix ratio chart by strength (psi)

The ratio you choose depends on the compressive strength the job needs, measured in psi (or MPa in Europe and Canada). Richer mixes with more cement reach higher strength concrete; leaner mixes suit non-structural concrete bases. This ratio chart covers the common mix designs.

Mix ratio (cement:sand:aggregate)	Approx. strength	Typical use
1:3:6	~1500 psi (10 MPa)	Lean base, levelling, blinding under footings
1:2:4	~2200 psi (15 MPa)	Standard general mix, small slabs, paths
1:2:3	~3000 psi (20 MPa)	Driveways, patios, footings, foundations
1:1.5:3	~4000 psi (27 MPa)	Heavy traffic driveways, structural slabs
1:1:2	~4500 to 5000 psi	Columns, beams, commercial building work

For most residential work the 1:2:3 mix is the default. The IRC sets a minimum of 2500 psi for footings and foundation walls, and most builders pour 3000 psi because the extra cost is small and it adds a safety margin against field variation.

Ratios that fall between two rows of this chart, such as 1:4:6 or 1:3:4, are not standard tabulated mixes. Judge them by cement richness: a ratio with less cement per part than 1:3:6 lands below 1500 psi and stays non-structural, while one between 1:3:6 and 1:2:4 lands roughly 1500 to 2200 psi.

The water-cement ratio matters most

The single biggest factor in concrete strength and durability is not the dry ratio, it is the water-cement ratio, the weight of water divided by the weight of cement. The relationship is inverse: less water means stronger, less permeable, more durable concrete.

The American Concrete Institute recommends a water-cement ratio between 0.45 and 0.60 for everyday use. A 0.50 ratio, about 5 gallons of water per 94 lb bag of portland cement, tends to give 4000 psi or more. Tightening to 0.45 pushes strength toward 4500 psi and sharply cuts permeability.

Permeability rises steeply above a water-cement ratio of 0.50, which lets water, chlorides and sulfates attack the concrete and any rebar inside. Every extra gallon per 94 lb cement bag can cut final strength by 500 to 700 psi.

If a low-water mix feels too stiff to place, do not add water. Use an admixture such as a plasticizer or superplasticizer to improve workability while keeping the low water-cement ratio that protects strength and durability.

Choosing the right mix for the job

Match the mix to the load. A garden path or shed base is fine on a 1:2:4 general mix, while a driveway that takes cars wants the 1:2:3 mix at around 3000 psi. For RVs or commercial trucks, step up to 1:1.5:3 for roughly 4000 psi.

Sand and stone also affect feel, not just strength. More sand gives better workability and a smoother finish, while more coarse aggregate makes a rockier, slightly stronger but stiffer mix. Decorative concrete usually leans on the sandier side for a cleaner surface.

If you are not sure which product matches your job, the guide to types of concrete lines up standard, high-strength, fiber-reinforced and rapid-set mixes against common tasks, so you pick the right bag before you start measuring parts.

Close up of cement, sand and coarse aggregate piles showing the proportions of a concrete mix ratio

Turning a ratio into bags and volume

A ratio tells you proportions, not quantities, so you need your total volume first. Add the parts together, then split the volume across them. A 1:2:3 mix has 6 parts total, so cement is one sixth of the dry volume, sand two sixths and aggregate three sixths.

Because the dry materials pack down when mixed with water, a rough rule is that it takes about 1.5 cubic feet of combined dry material to yield 1 cubic foot of concrete. Work out the cubic yards you need in the concrete calculator, then divide that volume into parts to buy the right cement, sand and stone.

parts total = cement + sand + aggregatecement volume = total concrete × (1 ÷ parts total)

If you would rather follow the math step by step for an odd shape, the walkthrough on how to calculate concrete shows how to convert dimensions into cubic yards before you split them into a mix ratio.

Mixing tips for strength and durability

Measure by volume with the same bucket or shovel for every part, so a 1:2:3 mix stays 1:2:3. Guessing proportions is the fastest way to a weak, crack-prone pour. Use clean sand and well-graded aggregate, since dirty or single-size stone weakens the bond.

Add water last and slowly. Mix to a workable but not soupy consistency, then stop. The mix should hold a slope when piled, not flow flat. Adding water to make placing easier is the classic mistake that quietly destroys strength.

Finally, cure properly. Concrete reaches most of its strength by 28 days, but only if it stays moist. Keep the surface damp for at least the first 7 days to reduce cracking and reach the design psi. Supplementary materials like fly ash can also improve workability and long-term durability in larger or ready-mix pours.

How we check this

Every formula is shown in full and verified with automated tests against manufacturer spec sheets and ASTM and ACI standards. We show our work so you can check it.

Frequently asked questions

Is 4 to 1 a good concrete mix?

A 4 to 1 mix (4 parts combined aggregate to 1 part cement) is fine for general, non-structural concrete like footings and bases, giving roughly 3000 psi. For driveways or structural work, a richer mix such as 1:2:3 or 1:1.5:3 gives more reliable strength.

What is the strongest concrete ratio?

Among common hand-mixed ratios, 1:1:2 (1 cement, 1 sand, 2 aggregate) is the strongest, reaching about 4500 to 5000 psi. The single biggest factor is still a low water-cement ratio near 0.40, which can push a rich mix past 5000 psi.

What is the 1/2/3 rule for concrete?

The 1:2:3 rule means 1 part cement, 2 parts sand and 3 parts coarse aggregate by volume, with about 0.5 parts water. It produces around 3000 psi concrete, the standard for residential slabs, patios, footings and driveways.

What is poor man's concrete?

Poor man's concrete is an informal term, usually meaning either a lean cement-and-gravel mix or the dry-pour method, where dry cement is spread over gravel and then misted with water. It is cheaper but weaker and less reliable than a properly proportioned, wet-mixed 1:2:3 concrete.

How much water do I add to a concrete mix?

Aim for a water-cement ratio of about 0.45 to 0.50 by weight, which is roughly 5 gallons of water per 94 lb bag of cement for 3000 to 4000 psi concrete. Add water gradually and stop at a workable, not runny, consistency.

What psi does a 1:4:6 concrete mix make?

1:4:6 is not a standard tabulated ratio, but it has less cement per part than the lean 1:3:6 base mix (about 1500 psi), so expect strength below 1500 psi, non-structural only. Use it for blinding, levelling or sub-base fill, not for footings or slabs. For a guaranteed psi, pick one of the ratios in the chart above or order design-mix ready concrete.

What psi is a 1:3:4 concrete mix?

1:3:4 sits between the lean 1:3:6 base mix (about 1500 psi) and the 1:2:4 general mix (about 2200 psi) in cement richness, so expect roughly 1800 to 2000 psi, fine for garden paths and non-structural slabs. Nominal ratios like this vary with water content and aggregate grading, so treat it as an estimate, not a guaranteed number.

Concrete Mix Ratio: Cement, Sand and Aggregate by Strength

Key takeaways