The standard concrete mix ratio is 1:2:3 — 1 part portland cement, 2 parts sand, and 3 parts gravel (coarse aggregate), by volume. Add roughly half a part of water (a water-to-cement ratio near 0.5) and you get a general-purpose concrete of about 3,000 psi — strong enough for most slabs, footings, and posts.
Those numbers are parts, not pounds: one bucket of cement, two of sand, three of gravel. Bagged mixes like Quikrete already blend cement, sand, and stone in the right proportions, so for a bag you just add water — the ratio matters when you batch from separate materials.
What the numbers mean
A mix ratio lists cement first, then sand (fine aggregate), then gravel or crushed stone (coarse aggregate). 1:2:3 means for every shovel of cement you add two of sand and three of stone. Cement is the glue; sand fills the gaps between stones; stone gives the mix its bulk and strength. Water triggers the chemical reaction (hydration) that hardens everything — it is not just there to make the mix wet.
Mix ratios by strength
Stronger concrete uses more cement relative to aggregate. A rough guide: 1:3:5 is a lean ~2,000 psi mix for non-structural fill; 1:2:3 is the all-purpose ~3,000 psi mix for slabs and footings; 1:1.5:3 reaches about 4,000 psi for driveways and heavier loads. When in doubt, 1:2:3 is the safe default for DIY work.
The water-to-cement ratio is the strength lever
More water makes concrete easier to place but weaker — every extra cup dilutes the paste. Aim for a water-to-cement ratio around 0.45 to 0.55 by weight, which for an 80 lb bag is roughly 3 quarts of water. The mix should be plastic and workable, holding its shape on a shovel, not soupy. Err dry: you can always add a splash, but you cannot remove water once it is in.
Scaling a batch
Pick a unit — a bucket, a shovel, a wheelbarrow scoop — and keep it consistent. For a small repair, 1 part cement might be one bucket; for a slab, batch in wheelbarrow loads. Mix the dry materials first until the color is uniform, then add water gradually. To skip the math entirely, use bagged mix and the bag calculator below to get your count.
Common questions
What is the 1:2:3 concrete mix ratio?
1 part cement, 2 parts sand, 3 parts gravel, by volume, with about 0.5 part water. It yields roughly 3,000 psi general-purpose concrete.
How much water do I add to a concrete mix?
About a 0.5 water-to-cement ratio — roughly 3 quarts per 80 lb bag. Aim for a plastic, workable mix, not soupy; too much water weakens it.
Is a higher cement ratio stronger?
Yes, up to a point. More cement relative to aggregate (e.g. 1:1.5:3) raises strength, but the water-to-cement ratio matters more — keep water low.