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Cement Calculator

Construction

Calculate how many 94 lb bags of cement you need for a concrete pour at your mix ratio. Enter volume and cement, sand, and gravel ratio for a fast estimate.

12,000
13
15
16
0.52

94 lb Bags Needed

6
Cement Volume
5.94

This calculator computes your 94 lb Bags Needed, Cement Volume from the values you enter.

Inputs
Total Concrete VolumeMix Ratio — CementMix Ratio — SandMix Ratio — GravelBag Yield
Outputs
94 lb Bags NeededCement Volume

What is a Cement?

A Cement Calculator determines how many 94 lb bags of Portland cement you need for a concrete pour, based on the total volume of concrete you're placing and your chosen mix ratio of cement to sand to gravel. Concrete mix design is proportional — a standard 1:2:4 ratio means one part cement to two parts sand to four parts gravel by volume — and this calculator applies that ratio along with the industry-standard wet-to-dry volume conversion to give you an accurate bag count.

This tool is built for anyone pouring a slab, footing, sidewalk, or foundation who needs to know exactly how much cement to buy before the job starts. Enter your total concrete volume and mix ratio, and the calculator handles the dry-volume conversion and proportional math automatically. If your project also needs bulk sand or gravel estimates, the Sand Calculator and Cubic Yard Calculator cover those related materials.

How to use this Cement calculator

  1. Enter your Total Concrete Volume in cubic feet — the finished, wet volume of the slab, footing, or structure you're pouring.
  2. Set the Mix Ratio — Cement value — typically 1 for a standard mix.
  3. Set the Mix Ratio — Sand value — typically 2 for a standard 1:2:4 mix.
  4. Set the Mix Ratio — Gravel value — typically 4 for a standard 1:2:4 mix.
  5. Set the Bag Yield — the cubic feet of cement per 94 lb bag (1 ft³ is standard).
  6. Review the Bags Needed result for your purchase order, and check Cement Volume to verify the underlying calculation.

Formula & Methodology

The calculator converts wet volume to dry volume, then applies the mix ratio:

Dry Volume (ft³) = Total Concrete Volume × 1.54

Cement Fraction = Mix Ratio Cement ÷ (Mix Ratio Cement + Mix Ratio Sand + Mix Ratio Gravel)

Cement Volume (ft³) = Dry Volume × Cement Fraction

Bags Needed = ceil(Cement Volume ÷ Bag Yield)

Worked example: A 27 ft³ pour (1 cubic yard) at a standard 1:2:4 mix ratio, with a 1 ft³ bag yield:

Dry Volume = 27 × 1.54 = 41.58 ft³

Cement Fraction = 1 ÷ (1 + 2 + 4) = 0.1429

Cement Volume = 41.58 × 0.1429 = 5.94 ft³

Bags Needed = ceil(5.94 ÷ 1) = 6 bags

Frequently Asked Questions

First convert your wet concrete volume to dry volume by multiplying by 1.54, which accounts for the volume reduction that happens when dry materials are mixed with water. Then multiply the dry volume by the cement's fraction of your mix ratio, and divide by the volume yield of a single bag to get the bag count.
Concrete ingredients — cement, sand, and gravel — shrink in total volume once mixed with water because the fine particles fill the gaps between coarser particles. The industry-standard 1.54 factor accounts for this, meaning you need about 54% more dry material volume than your final wet concrete volume.
A common general-purpose mix ratio is 1:2:4 (cement:sand:gravel), used for most residential slabs, footings, and foundations. Higher-strength applications may use 1:1.5:3, while less critical fill applications can use leaner ratios like 1:3:6.
Dry Volume = 27 × 1.54 = 41.58 ft³, Cement Fraction = 1 ÷ (1+2+4) = 0.143, Cement Volume = 41.58 × 0.143 = 5.94 ft³, and at 1 ft³ per 94 lb bag, that's 6 bags (rounded up). Use the calculator above with your exact volume and mix ratio for a precise count.
A single 94 lb bag of Portland cement yields approximately 1 cubic foot of cement material itself, but when combined with sand, gravel, and water at a standard 1:2:4 ratio, it contributes to roughly 4.5 cubic feet of finished concrete. This calculator uses cement volume directly rather than finished concrete yield per bag, since bag yield can vary by manufacturer.
Enter your Total Concrete Volume in cubic feet, set your Mix Ratio for cement, sand, and gravel as relative numbers (like 1, 2, and 4), and set the Bag Yield — the cubic feet of cement in a single bag. The calculator returns Bags Needed and the total Cement Volume required.
A 1:2:4 (cement:sand:gravel) ratio is standard for driveways, patios, and most flatwork, providing adequate strength for typical loads. Structural elements like footings or load-bearing slabs may call for a richer 1:1.5:3 mix — check local building code or an engineer's specification for critical structures.
You can't purchase a fraction of a bag, so the calculator always rounds up to ensure you have enough cement to complete the pour without running short mid-job. Any leftover cement can typically be resealed and used on a future project if kept dry.
Wet volume is the final volume of poured, set concrete — what you're measuring when you plan a slab's dimensions. Dry volume is the combined volume of the loose, unmixed dry ingredients before water is added, which is larger due to the 1.54 shrinkage factor.
Standard US cement bags weigh 94 lb and are widely treated as yielding about 1 cubic foot of material, but always check your specific product's packaging, since some regional or specialty cements may differ. Adjust the Bag Yield input in the calculator to match your actual product.
Using the same dry volume and mix ratio, sand volume follows the same proportional logic as cement — multiply dry volume by the sand fraction of your ratio. Use the [Sand Calculator](/sand-calculator/) to work out the sand-specific volume and weight for your project.
Also known as
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