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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.

Reviewed by the thecalcu.com team · Last updated July 20, 2026

12,000
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0.52

94 lb Bags Needed

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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.

Why Use a Cement Calculator?

Running short on cement mid-pour is a serious problem, concrete needs to be placed continuously to avoid cold joints and weak spots, so an inaccurate bag estimate can compromise the structural integrity of a slab. This calculator removes the guesswork by applying the correct wet-to-dry volume factor and mix ratio math automatically, so you order the right amount the first time.

A typical use case is a DIY homeowner pouring a small concrete pad or footing, entering the total volume and a standard 1:2:4 mix ratio immediately shows how many bags to buy at the hardware store. Contractors managing larger pours can also use this calculator to quickly cross-check a concrete supplier's bag-count recommendation or to plan a bagged-cement mix for a job too small to justify a ready-mix truck. If you also need to know how much rebar to reinforce the pour, the Rebar Calculator covers that separately.

Who Should Use This Calculator?

  • DIY homeowners pouring small slabs, footings, or fence post bases who are buying bagged cement rather than ready-mix.
  • Contractors cross-checking supplier bag-count quotes or planning bagged-mix pours for smaller jobs.
  • Masons calculating cement needs for mortar-adjacent concrete work like footings and foundations.
  • Landscapers pouring concrete footings for retaining walls, posts, or paver bases.
  • Construction estimators budgeting material costs for concrete line items on a project bid.

Anyone also estimating loose aggregate for the same pour may want the Sand Calculator or Square Feet to Cubic Yards Calculator for related volume conversions.

What Insights Does the Cement Calculator Give You?

The calculator returns two figures. Bags Needed is the final, rounded-up purchase quantity, this is the number to bring to the hardware store or add to your materials order. Cement Volume shows the precise cubic footage of cement required before rounding to whole bags, which is useful for cross-checking against a supplier's bulk cement quote or for fine-tuning your mix ratio.

Together these figures let you both shop accurately (Bags Needed) and verify the underlying math (Cement Volume) if you're comparing mix ratios or bag sizes. If your pour also needs reinforcement, pair this with the Rebar Calculator to complete your structural materials list.

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.
Show formula & methodology ↓Show less ↑

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

How do I calculate how many bags of cement I need?
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.
Why do you multiply by 1.54 for dry volume?
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.
What is a standard concrete mix ratio?
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.
How many bags of cement do I need for a 27 cubic foot pour at a 1:2:4 ratio?
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.
How much concrete does one 94 lb bag of cement make?
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.
How do I use the Cement Calculator?
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.
What mix ratio should I use for a driveway or patio slab?
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.
Why is my bag count always rounded up?
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.
What is the difference between wet and dry concrete volume?
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.
Does bag yield vary between cement brands?
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.
How much sand and gravel do I need alongside my cement?
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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