Concrete Calculator

United States · loose volumes · not a strength design

Concrete Materials Calculator

Estimate loose cement, sand, and coarse aggregate (gravel or stone) for a finished volume of concrete. People sometimes look for a cement calculator or a mix ratio such as 1:2:4. Cement alone is not concrete. Concrete is cement, sand, stone, and water working together. This page is a planning split of loose volumes. It is not a mix design and it does not promise strength.

How much cement, sand, and gravel are in a concrete mix?

Split the finished volume by the loose parts you type, such as 1:2:4, then multiply by a yield factor you also type. Loose cement, sand, and gravel take more room than finished concrete because of voids. This page does not assign PSI, does not prescribe water, and does not insert 1.54. Bags here are cement only.

How do I use this concrete materials calculator?

Enter a finished volume, the loose-volume parts, and a yield factor from a trial or a supplier.

  1. Type the finished concrete volume in cubic feet or cubic yards. Get that volume from the home calculator if the shape is not a simple number you already know.
  2. Leave extra allowance at 0 if that volume already includes waste. Do not add the same allowance twice.
  3. Type cement, sand, and stone as loose-volume parts, such as 1, 2, and 4. Those parts are your assumption. They are not a strength grade.
  4. Type the loose-volume factor from a trial batch or your supplier. Loose ingredients take more space than the finished concrete because of voids. This page does not fill in a factor.
  5. Choose Calculate. Cement bags appear only if you also open the optional cement mass fields and type both numbers.

Volume, parts, and factor

Finished concrete volume

Greater than zero. One cubic yard is 27 cubic feet. Switching units clears the result until you calculate again.

Starts at 0. Use 0 to 20. Type 0 when the home page already added allowance. It is added once here, and only if you type a number above 0.

Loose-volume parts

Cement : sand : coarse aggregate, by loose volume. All three must be greater than zero. Doubling every part, such as 2 : 4 : 8 instead of 1 : 2 : 4, does not change the split.

Loose-volume factor

Required. Leave it blank until a trial batch or supplier gives it. A factor of 1.5 would mean 1.5 cubic feet of loose cement, sand, and stone for each cubic foot of finished concrete. This page does not insert 1.54, 1.57, or any other typical factor.

Optional cement mass and bags

Leave both blank if you only need loose volumes. Cement mass needs a loose bulk density, in pounds per cubic foot of cement as poured into a container. That is not the particle density from specific gravity, which is near 196 lb/ft³ for many portland cements. A bag here is cement only. It is not a premixed concrete bag from the home page.

Results

Loose volumes use the factor and the parts you typed. They are not a recommended mix.

Loose ingredients

Total loose volume
Not calculated
Cement
Not calculated
Sand
Not calculated
Coarse aggregate
Not calculated

What was used

Finished volume entered
Not calculated
Same finished volume in cubic yards
Not calculated
Extra allowance entered
Not calculated
Target finished volume after that allowance
Not calculated
Loose-volume factor used
Not calculated
Parts used, cement : sand : stone
Not calculated
Total loose volume
Not calculated
Total loose volume in cubic yards
Not calculated
Cement loose volume
Not calculated
Sand loose volume
Not calculated
Coarse aggregate loose volume
Not calculated
Cement mass, if a loose bulk density was entered
Not calculated
Theoretical cement-only bags
Not calculated
Whole cement-only bags
Not calculated

How this split was figured

Loose volumes appear here after you enter a factor and a ratio. This page does not choose them for you.

How is the cement, sand, and gravel split figured?

Loose cement, sand, and stone take more space than the finished concrete, because finer particles fill gaps in the coarser ones. The factor you type is that extra space. Sand fills gaps in the stone, and cement paste fills gaps that remain. Water and air also take space. Adding the loose volumes does not equal the finished volume.

Cement Sand Stone Finished Loose volumes. Not to scale or a mix.
The three loose piles are measured by volume parts. They pack into a smaller finished volume. The factor you type is the loose total divided by that finished volume. The drawing is not to scale and is not a mix design.
  • Target finished volume = entered volume × (1 + extra allowance ÷ 100). At 0%, the target is the volume you typed.
  • Total loose volume = target finished volume × your factor.
  • Cement loose volume = total loose volume × cement parts ÷ (cement + sand + stone parts).
  • Sand and stone use the same split with their own parts.
  • Cement mass = cement loose volume × loose bulk density, only when you enter that density.
  • Whole cement bags = cement mass ÷ one bag’s weight, rounded up once. An exact number of bags is not increased.

Loose volume includes the air between particles. Absolute, or solid, volume is only the particles themselves. This page estimates loose volume. It does not convert specific gravity into absolute volume, and it does not prescribe water.

What does the 1:2:4 example arithmetic show?

With a hypothetical factor of 1.5 and no extra allowance, 28 cubic feet of finished concrete uses 6 cubic feet of loose cement, 12 of sand, and 24 of stone. That factor is not a recommendation.

The numbers below are hypothetical. They show the arithmetic only. They are not a recommended mix, not a typical factor, and not a measured cement density.

28 cubic feet, no extra allowance, factor 1.5, parts 1 : 2 : 4

  1. Target finished volume stays 28 cubic feet because the extra allowance is 0.
  2. Total loose volume is 28 × 1.5 = 42 cubic feet.
  3. Parts sum to 7. Cement is 42 × 1/7 = 6 cubic feet. Sand is 12 cubic feet. Stone is 24 cubic feet.
  4. If you also type a hypothetical loose bulk density of 94 lb/ft³, cement mass is 6 × 94 = 564 pounds.
  5. If one cement-only bag is also typed as 94 pounds, 564 ÷ 94 = 6 bags exactly.
  6. If that same 564 pounds is split into 80 pound cement-only bags, 564 ÷ 80 = 7.05, which rounds up once to 8 bags.

Why is the yield factor left blank?

No single loose-volume factor fits every mix. A trial batch or a supplier has to supply the number, so this page does not insert one.

Caltrans explains that a batch can list more loose cubic yards of cement, sand, gravel, and water than the concrete it yields, because finer material fills voids. One illustration in that manual is 9.1 cubic yards of listed ingredients yielding 7 cubic yards. That illustration includes water, and the manual presents it as an example, not a factor to copy onto every job.

The absolute-volume method used in mix proportioning divides each material’s weight by its specific gravity times the unit weight of water, then adds water and air. A first trial still has to be batched and adjusted. Portland Cement Association notes on aggregates say void content changes with shape and grading, and is measured by a bulk-density test such as ASTM C29. Those sources do not give one loose-volume factor for every mix. This page therefore leaves the factor blank.

None of those publications endorse the 1.5 factor or the 1 : 2 : 4 parts in the illustrative example.

What do people ask about mix ratios?

Is this a cement calculator?

It estimates cement together with sand and stone. Cement by itself is not concrete. The bags on the home page are premixed concrete, cement and aggregate already combined. A bag on this page, if you enter one, is cement only.

Why is the loose volume larger than the finished concrete?

Dry cement, sand, and stone have air gaps. Mixing lets smaller particles and paste fill those gaps, so the finished volume is smaller. The factor is how much loose volume you need for one unit of finished concrete. It changes with the materials, moisture, air, and how tightly they are measured.

Can you tell me which ratio to use?

No. A ratio such as 1 : 2 : 4 is only the loose-volume split you type. This page does not connect a ratio to psi, MPa, or an M grade, and it does not design a foundation or a structural mix.

Where do the factor and the cement density come from?

From a trial batch, a mix sheet, or the supplier. This page will not guess them. If either optional cement number is blank, mass or bag count stays unknown instead of being invented.

How is this different from the other pages?

Home estimates how much concrete to order. Concrete Blocks counts masonry units. Concrete Weight turns a volume and a density into pounds. This page splits a finished concrete volume into loose cement, sand, and stone. It does not add water, and it does not check strength.

What does this materials calculator refuse to decide?

It splits loose volumes with the parts and factor you type. It does not choose a PSI, a water amount, or a safe mix.

  • This is a loose-volume planning split. It is not a mix design, a strength calculator, or a structural approval.
  • The factor and the parts are the numbers you enter. There is no hidden 1.54 or 1.57.
  • Water, water-cement ratio, grading, moisture, entrained air, and compaction are not calculated. A trial batch is still required.
  • Loose volume is not the solid volume of the particles. Specific gravity is not accepted in the density box.
  • Sand and stone masses are not estimated. Cement mass and cement-only bags appear only when you type the needed numbers.
  • Extra allowance is 0 to 20 and is added once. Finished volume is limited to 100,000 cubic yards. Each part is limited to 100. The factor is limited to 5. Optional cement density and bag weight are limited to 200. These are limits of this page.
  • Do not add allowance here if the volume from the home page already includes it.