HomeMath

Concrete Mix Calculator

Enter the size of the pour or its volume and pick a mix ratio to get the 94 lb bags of Portland cement, the sand and gravel in cubic feet, cubic yards and tons, and the water at your water-cement ratio. A cubic yard of 1:2:3 concrete takes 7 bags of cement, 13.9 cu ft of sand and 20.8 cu ft of gravel.

Units
Mix ratio (cement : sand : gravel)

1:2:3: Quikrete's recipe for concrete from its Portland cement: 1 part cement, 2 parts sand, 3 parts gravel.

10 bags of cement (94 lb)

Concrete, waste included:
1.36 cu yd (36.67 cu ft)
Dry materials (× 1.54):
2.09 cu yd (56.47 cu ft)
Cement:
0.35 cu yd (9.41 cu ft), 885 lb
Sand:
0.70 cu yd (18.82 cu ft), about 0.98 tons
Gravel:
1.05 cu yd (28.23 cu ft), about 1.62 tons
Water at 0.50:
53.0 gallons (442 lb)

Buying premixed bags instead? The concrete calculator counts the 40 to 90 lb bags.

How HomeMath calculates a concrete mix

HomeMath takes the volume of concrete with its waste allowance and multiplies it by 1.54 for the dry materials, because sand fills the gaps in the gravel and cement fills the gaps in the sand. It splits that dry volume by the ratio's parts: for 1:2:3, one sixth cement, two sixths sand and three sixths gravel. Cement is counted in 94 lb bags of 1 cu ft and rounded up; sand and gravel go to tons at their published loose weights; the water is the cement's weight × the water-cement ratio, at 8.35 lb a gallon. In metric, the volumes are in cubic meters and liters, the cement in kilograms, the sand and gravel in tonnes and the water in liters.

The published rules it uses: concrete mix ratios; gravel weights and prices; US customary units; metric conversion. Their sources, and how HomeMath tests every result, are on the about page.

What do the numbers in a 1:2:3 mix ratio mean?

A ratio such as 1:2:3 gives the parts by volume: one bucket of cement, two of sand, three of gravel, so cement is 1 part in 6. Quikrete gives 1:2:3 as its recipe for concrete from its Portland cement. Inch Calculator lists the grades below, each with its compressive strength and the highest water-cement ratio for it: the more cement to the same sand and gravel, the stronger the concrete.

Concrete mix ratios by grade (Inch Calculator)
GradeCement : sand : gravelStrengthWater-cement, at most
M51:5:10725 psi0.60
M7.51:4:81,087 psi0.60
M101:3:61,450 psi0.60
M151:2:42,175 psi0.50
M201:1.5:32,900 psi0.45
M251:1:23,625 psi0.40

Which ratio for a slab, a footing or a post? The one your plans or local code ask for, by its strength. As a reference, Quikrete's premixed Concrete Mix reaches 4,000 psi at 28 days by its data sheet and is sold for footings, slabs, patios and post footings alike.

This counts the raw materials. Buying premixed bags that only need water is a different count: the concrete calculator gives those, and how many yards of concrete in a cement truck covers ready-mix.

How much cement, sand and gravel goes into a cubic yard?

Before waste, for one cubic yard of concrete at each preset ratio:

Materials per cubic yard
RatioCement, 94 lb bagsSandGravelWater
1:2:37 (6.93 cu ft)13.9 cu ft, 0.72 tons20.8 cu ft, 1.19 tons39 gal at 0.50
1:2:46 (5.94 cu ft)11.9 cu ft, 0.62 tons23.8 cu ft, 1.36 tons33 gal at 0.50
1:1.5:38 (7.56 cu ft)11.3 cu ft, 0.59 tons22.7 cu ft, 1.30 tons38 gal at 0.45
1:3:36 (5.94 cu ft)17.8 cu ft, 0.92 tons17.8 cu ft, 1.02 tons33 gal at 0.50

Sand is weighed as dry sand and gravel as #57 crushed stone, at the middle of Inch Calculator's loose weights; your supplier's ticket may differ, as wet sand weighs more.

How do you work out cement, sand and gravel by hand?

  1. Dry volume: 27 cu ft × 1.54 = 41.58 cu ft.
  2. Cement: 41.58 ÷ 6 (1 + 2 + 3) = 6.93 cu ft, so 7 bags of 94 lb (1 cu ft each).
  3. Sand: 6.93 × 2 = 13.86 cu ft (0.51 cu yd). Gravel: 6.93 × 3 = 20.79 cu ft (0.77 cu yd).
  4. Water at 0.50: 651 lb of cement × 0.50 = 326 lb, about 39 gallons.

Why × 1.54? Sand fills the gaps between the stones and cement the gaps in the sand, so the mixed concrete is smaller than its dry parts. The US Navy's builder manual gets the same result with its rule 41 and 42: 41 cu ft of dry materials per cubic yard with coarse aggregate up to 1 inch, 42 up to 2 1/2 inches. Sand is weighed as dry sand and gravel as #57 crushed stone, so a supplier's ticket for wet sand may differ.

What a yard, a slab, a footing and a walkway take

Each with 10% waste: the 94 lb bags of cement, then the sand and gravel. A 10 × 10 ft slab 4 inches thick at 1:2:3 takes 10 bags of cement, 18.8 cu ft of sand and 28.2 cu ft of gravel.

  • 1 cubic yard, 1:2:38 bags · 15.2 cu ft sand · 22.9 cu ft gravel
  • 10 × 10 ft slab, 4 in, 1:2:310 bags · 18.8 cu ft sand · 28.2 cu ft gravel
  • 10 × 10 ft slab, 4 in, 1:2:49 bags · 16.1 cu ft sand · 32.3 cu ft gravel
  • 40 ft footing, 16 × 8 in, 1:2:311 bags · 20.1 cu ft sand · 30.1 cu ft gravel
  • 1 cubic foot, 1:2:31 bag · 0.6 cu ft sand · 0.8 cu ft gravel
  • 4 × 30 ft walkway, 4 in, 1:1.5:313 bags · 18.5 cu ft sand · 37.0 cu ft gravel

What is the cement ratio of a mix, and how much water does it take?

The cement share of a mix is its part over the total: 1 in 6 for 1:2:3, 1 in 7 for 1:2:4. The water-cement ratio is a different number, by weight: 0.50 means half a pound of water per pound of cement. Lower ratios give stronger concrete; the mix still has to be workable, so add water a little at a time and stop when it places.

How does the mix work in metric?

Switch to metric for the pour in meters and centimeters or cubic meters; the cement comes out in kilograms (and the 94 lb bags), the sand and gravel in cubic meters and tonnes, and the water in liters. For a cement bag of another size, divide the kilograms by its weight.

Frequently asked questions

How do I work out cement, sand and gravel from a mix ratio?
Add up the parts and give each material its share of the dry volume: in 1:2:3 by volume, one part cement, two parts sand and three parts gravel, cement is one sixth, sand two sixths and gravel three sixths. 1:2:3 is Quikrete's recipe with its Portland cement. Inch Calculator lists stronger and leaner grades, from 1:5:10 at about 725 psi to 1:1:2 at about 3,625 psi. The strength your plans ask for sets the ratio.
How many bags of cement are in a yard of concrete?
7 bags of 94 lb for a 1:2:3 mix: a yard is 27 cu ft, × 1.54 = 41.58 cu ft dry, and one sixth of it is 6.93 cu ft of cement, rounded up to 7 bags. A 1:2:4 mix takes 6.
How much sand and gravel do I need for a yard of concrete?
For 1:2:3, 13.9 cu ft of sand (about 0.72 tons) and 20.8 cu ft of gravel (about 1.19 tons), before waste. Sand is weighed at 1.40 tons and #57 gravel at 1.55 tons a cubic yard, the middle of Inch Calculator's ranges.
How much water do I add to a concrete mix?
The cement's weight × the water-cement ratio. A yard of 1:2:3 at 0.50 takes 326 lb of water, about 39 gallons. Inch Calculator's grades allow 0.40 to 0.60 at most: less water gives stronger concrete, so add only what you need to place it.
What is the 1:2:4 concrete mix?
One part cement, two parts sand and four parts gravel by volume, Inch Calculator's M15 grade at about 2,175 psi with a water-cement ratio of 0.50 at most. A cubic yard takes 6 bags of cement, 11.9 cu ft of sand and 23.8 cu ft of gravel.
Is it cheaper to mix my own concrete or buy bags?
Price both at your store: the cement, sand and gravel this calculator lists against the premixed bags the concrete calculator counts. Mixing from raw materials saves carrying bags of premix but adds batching each load by hand.
Why is the dry volume bigger than the concrete?
Because sand and cement fill the gaps between the stones, the mixed concrete takes less room than its dry parts. HomeMath multiplies by 1.54, Inch Calculator's factor; the US Navy's builder manual uses 41 to 42 cu ft of dry materials per cubic yard, a factor of 1.52 to 1.56.
What mix ratio should I use for a slab, footing or post?
The one your plans or local code ask for, by its strength. HomeMath's sources name no ratio per job: Quikrete's general recipe is 1:2:3, and its bagged Concrete Mix, rated 4,000 psi at 28 days, is sold for footings, slabs, patios and post footings alike. A richer mix (more cement per part of sand and gravel) is stronger.

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