How it works
The calculator converts the finished volume to the volume of dry materials, splits it by the ratio, and turns the cement into bags.
Dry volume = Concrete volume × (41 or 42) ÷ 27 × (1 + Handling loss ÷ 100)
Cement, sand, gravel = Dry volume × Parts ÷ (Cement + Sand + Gravel parts)
Cement weight = Cement volume × 94 lb/cu ft
Bags = ⌈ Cement weight ÷ Bag weight ⌉
Water = Cement weight × Water–cement ratio
⌈ ⌉ means rounding up to the next whole bag. Sand and gravel are not rounded, because they are bought by volume or weight.
The Navy’s Builder manual (NAVEDTRA 14043) works the same example on its rule of 42: a 1:2:4 mix adds up to 7 parts, so 42 cu ft of dry material for a cubic yard is 6 cu ft of cement, 12 of sand and 24 of gravel. At 94 lb per cubic foot, that is 564 lb, or six bags. This tool estimates material quantity only; the mix for structural concrete comes from your plans, local code or a qualified professional.
Worked example
Inputs
- Concrete volume needed
- 1 cu yd
- Mix ratio (cement : sand : gravel)
- 1 : 2 : 4
- Largest gravel size
- Up to 2½ in (63 mm) – rule 42
- Cement bag weight
- 94 lb
- Handling loss
- 0 %
Result
- Bags of cement
- 6
- Sand
- 12 cu ft (0.444 cu yd)
- Gravel
- 24 cu ft (0.889 cu yd)
- Cement (loose volume)
- 6 cu ft (0.222 cu yd)
- Cement weight
- 564 lb (0.282 short tons)
- Dry materials in total
- 42 cu ft (1.56 cu yd)
Common mistakes
- Dividing the wet volume by the ratio. The dry ingredients shrink when water is added and the sand fills the gaps between the stones, so a cubic yard of concrete takes about 41–42 cu ft of dry material, not 27.
- Mixing ratios by weight and by volume. A 1:2:3 ratio here is by loose volume; a mix design given in pounds per cubic yard cannot be measured with a shovel the same way.
- Assuming every bag holds 1 cu ft. That is true of the 94 lb US bag of portland cement; smaller or metric bags hold less, so the calculator counts bags by weight.
- Choosing a ratio from a calculator for structural work. Footings, slabs that carry vehicles and anything reinforced need the mix your plans, local code or a qualified professional specify.
Assumptions and limits
- Dry volume = concrete volume × 41 ÷ 27 or 42 ÷ 27 (NAVEDTRA 14043 rule 41 or 42), split by the parts of the ratio.
- Loose cement weighs 94 lb per cubic foot (1,505.7 kg/m³), the US bag convention of FM 5-428 and NAVEDTRA 14043.
- The handling loss is added to all dry materials before the cement is turned into whole bags.
- Water, if a water–cement ratio is entered, is cement weight × ratio at 1 kg per liter (about 8.34 lb per US gallon).
- The result is a material quantity only, not a mix design or a structural design.
Frequently asked questions
How much cement, sand and gravel is in a cubic yard of 1:2:3 concrete?
With gravel up to 1 in, the rule of 41 gives 41 cu ft of dry material, split 1:2:3 into about 6.8 cu ft of cement (7 bags of 94 lb), 13.7 cu ft of sand and 20.5 cu ft of gravel, before any handling loss. QUIKRETE’s portland cement data sheet says five to six 94 lb bags are typically used per cubic yard with appropriate proportions of sand and gravel, so check your own mix.
What is the 1.5 or 1.54 dry volume factor?
It is the same idea as the Navy’s rule of 41 or 42. 41 ÷ 27 = 1.52 and 42 ÷ 27 = 1.56, so a cubic yard of concrete needs roughly half as much again in dry materials.
Which mix ratio should I use?
Use the one in your plans, specification or on the product label. 1:2:3 is a common general-purpose mix on cement bags and in the Army’s FM 5-428; stronger or leaner mixes exist for other jobs. This calculator does not choose a mix for you.
Can I use metric bags?
Yes. Switch to metric, enter the volume in cubic meters and the bag weight printed on your bag, for example 25 kg. The bag count is cement weight ÷ bag weight, rounded up.
How much water do I add?
Enter a water–cement ratio from your mix design to estimate it. Water is added gradually in practice, and sand that is already damp needs less.
Sources
- Builder 3 & 2, Volume 1 (NAVEDTRA 14043), chapter 6 – Concrete — U.S. Navy, Naval Education and Training Professional Development and Technology Center (public-domain copy hosted by ConstructionKnowledge.net). "A 94-pound sack of cement amounts to about 1 cubic foot by loose volume"; rule 41 or 42: "it takes either 41 or 42 cubic feet of the combined dry amounts of cement, sand, and aggregates to produce 1 cubic yard of mixed concrete" (41 for coarse aggregate not over 1 in, 42 for not over 2 1/2 in); worked 1:2:4 example "6 + 12 + 24 = 42"; handling loss 5 % for 200 cu yd or more, 10 % for smaller jobs (default 10 %).
- FM 5-428 Concrete and Masonry — Headquarters, Department of the Army (copy hosted by vulcanhammer.net). "a standard sack of portland cement weighs 94 pounds and equals 1 loose cubic foot"; "the 1:2:3 method … 1 part cement, 2 parts sand, and 3 parts aggregate"; normal-weight concrete "weighs 135 to 160 pounds per cubic foot".
- QUIKRETE Portland Cement (No. 1124, 1125) Product Data Sheet, rev. August 2022 — The QUIKRETE Companies. Bags of 31, 47 and 94 lb (and 40, 42 kg); typical concrete mix "1 Part QUIKRETE Portland Cement, 2 Parts QUIKRETE All-Purpose Sand, 3 Parts QUIKRETE All-Purpose Gravel"; "five to six 94 lb (42.6 kg) bags … to produce 1 cu. yd."
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 6, 2026