Cement Calculator: Bags of Cement, Sand and Gravel

Quick answer

Published 2026-10-21 · Ratios from the Quikrete and Sakrete portland cement sheets and PCA's Design and Control of Concrete Mixtures (Tables 9-16 and 9-17). No built-in prices. Buying premix instead? Our concrete bag calculator counts 40, 60 and 80 lb bags.

How to use the cement calculator

1. Enter the slab or footing size, or type the volume you already know (for round piers use our concrete column calculator first, then enter its cubic feet here).
2. Keep a 5–10% waste allowance for spillage and an uneven base.
3. Pick the mix. The 1:2:3 recipe is the one on Quikrete and Sakrete portland cement bags; the PCA presets follow the maximum size of your gravel; choose the sand mix for toppings thinner than 2 in.
4. Leave the yield factor at 2/3 unless you have tested your own sand and gravel: it is PCA's published rule and asks for more cement than the bag makers' own yield figures.
5. Optionally add your local prices to see whether mixing from scratch beats premix bags for this job.

Assumptions & formula

• Volume: V (ft³) = length × width × thickness (in) ÷ 12, times (1 + waste %). 1 yd³ = 27 ft³; 1 m³ = 35.3147 ft³.
• Mix: parts c : s : g are loose (bulk) volumes. Mixed concrete = F × (c + s + g) parts, so cement volume = V × c ÷ (F × (c + s + g)). F = 2/3 from PCA Table 9-17: "The combined volume is approximately 2/3 of the sum of the original bulk volumes."
• Cement bags: 1 bag = 94 lb = 1 ft³ (Sakrete sheet: "This bag contains 94 lbs. or 1 cu. ft."); bags are rounded up; a 47 lb bag counts as half.
• Sand and gravel weight: 80–90 lb per loose ft³ of sand and 80–100 lb per ft³ of gravel, from Sakrete's "2 parts sand (160–180 lbs.)" and "3 parts gravel (240–300 lbs.)" per bag. Wet or dense local material can weigh more.
• Water: 1:2:3 mix, about 6 gal per bag (Sakrete); PCA presets, 1/2 part water by bulk volume (1 ft³ = 7.48 gal), with damp aggregates. Treat both as a starting point.
• Premix comparison: 80 lb premix bag = 0.60 ft³ (Quikrete Concrete Mix No. 1101 data sheet), the same yield as our concrete bag calculator.

How many bags of cement per cubic yard, for each mix?

A cubic yard needs between 6.23 and 8.10 bags of 94 lb cement across the PCA gravel sizes, and 6.75 for the 1:2:3 bag recipe, because a bigger gravel leaves less space for paste. The table runs the calculator once per mix for exactly 27 ft³ (no waste); bags to buy in brackets.

Two practical readings: switching from 3/4 in to 3/8 in gravel at the same sand share costs about 1.4 extra bags per yard, and the air-entrained PCA mix uses slightly less sand but 0.29 more cement per yard than the plain 3/4 in mix because its parts add up to less.

Does the 2/3 rule agree with PCA's mix-by-weight table?

Closely, but not exactly: the bulk-volume method on PCA's Table 9-17 ratios gives 3–6% fewer bags per yard than PCA's own mix-by-weight Table 9-16 for every gravel size, so if you weigh your materials, expect about half a bag more per yard than the 2/3 rule says. Table 9-16 lists pounds of cement per cubic foot of non-air-entrained concrete; we multiplied by 27 and divided by 94.

The bag makers sit on the other side: Sakrete's "one 94 lb. bag ... makes 4.5 cubic feet" means 6 bags per yard at 1:2:3, and Quikrete's "five to six 94 lb bags" per yard means 4.5–5.4 ft³ per bag. So the 2/3 rule sits between the two published views: it asks for about 0.75 bag per yard more than Sakrete's yield and about 0.4 bag less than PCA's mass table. Choose 0.75 only if you trust the bag maker's figure for your own sand and gravel.

Worked example: a 10×10 ft slab, 4 in thick

A 10×10 ft slab 4 in thick with 10% waste is 36.67 ft³ (1.36 yd³) and needs 10 bags of portland cement, 18.3 ft³ of sand and 27.5 ft³ of gravel at 1:2:3, or 62 bags of 80 lb premix. The materials weigh about the same either way: 4,607–5,340 lb mixed from scratch versus 4,960 lb of premix.

With example prices of $15 per cement bag, $40 per ton of sand, $45 per ton of gravel and $6 per premix bag (inputs to show the arithmetic, not prices we collected), the slab costs $228.83–$244.88 from scratch and $372.00 in premix. Delivery of loose sand and gravel, a mixer and your time are not in either figure.

How much cement, sand and gravel for common slab sizes?

Each 100 ft² of 4 in slab takes about 10 bags of portland cement at 1:2:3 once 10% waste is added. The table repeats the calculation for common pads; premix bag counts are alongside for comparison.

How do I measure a concrete mix with a bucket?

Use the same container for every part: with a 5-gallon bucket (0.668 ft³), one bucket of cement, two of sand and three of gravel make about 2.67 ft³ of 1:2:3 concrete, roughly the output of 4.5 premix bags. A 94 lb bag of cement fills about 1.50 buckets, so one bag is one full batch of a 1:2:3 recipe and a half.

Mix the dry parts first, then add water a little at a time; a bucket batch of 1:2:3 takes about 4.0 gallons by Sakrete's 6-gallons-per-bag guide, less if the sand is wet.

Result looks wrong? Check these

• Bags look high compared with the bag label: the 2/3 factor gives more bags than the 4.5 ft³ per bag printed by Sakrete; switch to 0.75 to match it, or keep the extra bag as a margin.
• Sand and gravel look like too little: they are loose volumes for the whole job, not per batch, and the mix shrinks to about 2/3 of the loose total when the sand fills the gaps in the gravel.
• Custom ratio gives far more cement than expected: check the order. The calculator reads cement : sand : gravel, so 1:2:4 means 4 parts gravel.
• Thickness typed in feet: 0.33 in is not 4 in; thickness is in inches.
• Water seems high for the PCA presets: it is not; at 1/2 part water the PCA mix uses less water per bag than the 6 gallons Sakrete prints, because PCA's sand is already damp.

When not to use this calculator

• Structural or specified concrete (footings under a building, driveways in freeze-thaw areas): your code or engineer specifies strength and air content; order ready-mix or a rated premix rather than a site volume mix.
• More than about 1 yd³: PCA describes site-mixed batches for small jobs of about one cubic yard or less; for bigger pours compare bags and a truck with our concrete slab cost calculator.
• Mortar or stucco: they use masonry sand and lime, not gravel; see the mortar calculator.

Frequently asked questions

Sources

• Portland Cement Association, Design and Control of Concrete Mixtures, EB001, 14th ed., Chapter 9, Tables 9-16 (proportions by mass for small jobs) and 9-17 (proportions by bulk volume, note on the 2/3 combined volume) (retrieved 2026-10-21).
• Quikrete, Portland Cement data sheet (© 2022): concrete mix 1 part cement, 2 parts sand, 3 parts gravel by volume; "five to six 94 lb bags ... to produce 1 yd³"; bag sizes 47 and 94 lb (retrieved 2026-10-21).
• Sakrete, Portland Cement Type I-II product sheet: 94 lb = 1 cu ft; 2 parts sand 160–180 lb, 3 parts gravel 240–300 lb; about 6 gal water; 4.5 ft³ per bag; 1:3–4 sand mix under 2 in (retrieved 2026-10-21).
• Quikrete, Concrete Mix No. 1101 data sheet: 80 lb bag yields 0.60 ft³ (retrieved 2026-10-15).
• NIST Handbook 44 (2024), Appendix C: 1 US gallon = 231 in³; 1 yd³ = 27 ft³ = 0.764555 m³.

Related calculators & guides

• Bags of premixed concrete for a job
• Quikrete bag counts by product
• Sakrete bag counts by product
• Concrete slab volume in yards
• Bags vs ready-mix slab cost
• Footing volume
• Mixing and pouring in cold weather

Last updated 2026-10-21 · About TrueToolCalc and how we check numbers · Found an error? Use the contact page.