Loan Concrete Mix Estimator
Bagged mix hides the recipe; site mixing shows it. Enter the volume and the ratio your job specs — 1:2:4 for most slabs, 1:1.5:3 for structural work — and get cement bags, sand, aggregate and water as a real shopping list.
Volume is finished, in-place concrete. Don't know it yet? The Concrete Calculator turns slab, footing, tube, step and curb dimensions into cubic yards — bring that number here.
How it works
Dry ingredients bulk larger than the wet volume they make: the industry dry-volume factor is 1.54 (voids in the aggregate collapse as water and cement fill them). So 2 cu yd of placed concrete needs 83.16 cu ft of dry material, split by ratio parts. Cement is counted in 94-lb bags of 1 cu ft each. Sand converts at 1.40 tons per yard, coarse aggregate at 1.50. Water runs about 5.5 gallons per bag at a 0.50 water-cement ratio — the strength line: more water pours easier and cures weaker, permanently.
Formula & worked example
Formula: Dry volume = wet volume × 27 × 1.54. Split by ratio parts; cement counted in 94-lb bags of 1 cu ft; sand at 1.40 tons per yard, aggregate at 1.50; water ≈ 5.5 gal per bag at a 0.50 water-cement ratio.
Worked example: Two cubic yards of 1:2:4: 12 cement bags, 0.88 cu yd sand (1.23 tons), 1.76 cu yd aggregate (2.64 tons), about 66 gallons of water.
When to use this
- You are site-mixing concrete and need the raw-materials shopping list.
- A spec gives a ratio (1:2:4) and you need bags, sand and stone by the yard.
- You are comparing site-mix cost against ready-mix for a mid-size pour.
How to use it, step by step
- Get the finished volume in cubic yards (the Concrete Calculator computes it from dimensions).
- Select the mix ratio the job requires.
- Read cement bags, sand and aggregate in yards and tons.
- Note the water figure — it is a strength spec, not a suggestion.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Volume | Finished, in-place concrete | 0.5 yd small footing runs; 2+ yd slabs |
| Mix ratio | Cement : sand : aggregate by volume | 1:2:4 general; 1:1.5:3 structural; 1:3:6 lean fill |
Another worked example
One cubic yard of structural 1:1.5:3: the dry pile is 41.58 cu ft; cement takes 1/5.5 of it — 8 bags — with 0.42 cu yd of sand (0.59 tons), 0.84 cu yd of aggregate (1.26 tons) and about 44 gallons of water. Compare the 12-bag, general-purpose 1:2:4 recipe for two yards in the formula card.
Frequently asked questions
What do I need for 2 yards of 1:2:4 concrete?
Twelve 94-lb cement bags, 0.88 cu yd of sand (about 1.23 tons), 1.76 cu yd of aggregate (about 2.64 tons) and roughly 66 gallons of water. The dry pile always looks impossibly big — the 1.54 factor is real.
How much cement in 1 yard of 1:1.5:3?
Eight bags: 41.58 cu ft of dry material, of which cement is 1/5.5 — 7.56 cu ft, rounded to 8 bags — plus 0.42 yd of sand and 0.84 yd of aggregate. Richer mixes buy strength with cement, and cement is the expensive part.
What do the ratios mean in strength?
Roughly: 1:3:6 ≈ 1,500 psi class (blinding, fill), 1:2:4 ≈ 2,500–3,000 psi (slabs, footings), 1:1.5:3 ≈ 3,500–4,000 psi (structural). Actual strength depends on water content and curing as much as the ratio.
Why 1.54 times the volume?
Loose dry aggregate is full of air gaps. Cement and sand fill the gaps in the stone; water fills the gaps in the sand. The placed volume is what remains — empirically about 65% of the dry pile, hence ×1.54 going the other way.
Can I just buy bagged mix instead?
For small work, yes — the Concrete Calculator counts 60- and 80-lb pre-mix bags by shape. Past roughly 60–80 bags, bulk materials or ready-mix win on both cost and your back.
🏗️ Need the volume from dimensions?
The Concrete Calculator turns slabs, footings, tubes, steps and curbs into cubic yards and bag counts — then this page turns the yards into a mix recipe.
What is the strongest mix I can make on site?
1:1.5:3 at a strict 0.45–0.50 water-cement ratio with good curing reaches the 3,500–4,000 psi class. Past that, admixtures and plant quality control matter more than ratio — that is ready-mix territory.
Can I add a bag of cement to 'strengthen' a bagged mix?
You can enrich pre-mix modestly, but water discipline matters more: a sloppy-wet 1:1.5:3 pour cures weaker than a stiff, well-cured 1:2:4. Measure water; do not hose by feel.