Concrete materials calculator
Enter the dimensions of the pour and pick a mix ratio. The tool works out the wet volume, multiplies it by the dry volume factor, and splits the result across the parts of the mix. That middle step is the one people skip, and it is why materials turn up short.
1:2:4 for slabs and footings, 1:1.5:3 for columns and beams, 1:3:6 for blinding and non-structural work.
Default price from the Saudi Arabia market — checked August 2026 — change it to the quote you were given.
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Cement bags
10 bags
To pour 1.5 m³ at 1:2:4
Breakdown
| Wet volume | 1.5m³ |
| Dry volume factor | × 1.54 |
| Dry volume | 2.31m³ |
| Cement by volume | 0.33m³ |
| Cement by weight | 475.2kg |
| Sand | 0.66m³ |
| Sand in tonnes | 1.06 |
| Aggregate | 1.32m³ |
| Aggregate in tonnes | 1.98 |
| Approximate water | 238L |
| Cement cost | 150.00 |
These quantities are for mixing on site. Ready-mix is ordered by the wet cubic metre, so do not apply the dry volume factor when ordering from a batching plant. The water figure is indicative and moves with admixtures and site conditions.
How it's calculated
The wet volume is the volume of the finished element: area times thickness for a slab, or length times width times height times the count for a column. That is what you will see after the pour, but it is not what you have to buy.
Dry materials shrink when they are mixed, because the cement and sand settle into the voids between the aggregate. So the wet volume is multiplied by 1.54 to give the dry volume, which is the quantity of loose material that actually has to arrive on site.
The dry volume is then divided by the total parts in the mix. In a 1:2:4 mix the total is seven, so cement is one seventh of the dry volume, sand two sevenths and aggregate four sevenths. The cement volume is converted to kilograms by its bulk density and then to 50 kg bags, rounded up.
- Wet volume = area × thickness, or length × width × height × count
- Dry volume = wet volume × 1.54
- Each material = dry volume × its part ÷ total parts
- Cement bags = cement volume × 1440 ÷ 50, rounded up
- Approximate water = cement weight × 0.5
Worked example
A 10 m² slab at 15 cm thick, mixed 1:2:4:
- Wet volume: 10 × 0.15 = 1.5 m³
- Dry volume: 1.5 × 1.54 = 2.31 m³
- Parts in the mix: 1 + 2 + 4 = 7
- Cement: 2.31 ÷ 7 = 0.33 m³, which is 475 kg, or 9.5 bags
- Sand 0.66 m³ and aggregate 1.32 m³
You need 10 bags of cement, 0.66 m³ of sand and 1.32 m³ of aggregate. Buying against 1.5 m³ instead of 2.31 would have left you roughly a third short.
FAQ
What is the 1.54 factor and why can I not ignore it?
Because loose dry materials have air voids between them that disappear once mixed. One cubic metre of compacted concrete needs about 1.54 cubic metres of loose material. Order against the wet volume and you will be roughly a third short, which is the single most common error in hand-calculated small pours.
Does the factor apply to ready-mix?
No. A batching plant sells you the wet cubic metre, finished. Order 1.5 m³ in the example above and add a small allowance for what is lost in transport and placing. The dry volume factor is only for mixing on site.
Which mix should I use?
1:2:4 is the everyday mix for slabs, footings and ground beams, roughly C20/25. 1:1.5:3 is richer in cement and is used for columns, beams and anything carrying concentrated load, roughly C25/30. 1:3:6 is a blinding mix under footings and is never structural. The structural drawings are the final word.
How much water do I add?
The figure shown is half the weight of the cement, a water-cement ratio of 0.5, which gives a workable mix without plasticisers. More water places more easily but drops the strength noticeably, and damp sand already carries water that has to be deducted. Treat it as a starting point, not a recipe.
Do the quantities include site waste?
No. The 1.54 factor covers the volume shrinkage, not what is spilled. Add 5 to 10 percent on top to cover losses in transport and placing, and more if the pour is by hand or the weather is hot.
Related tools
Sources
✓ Reviewed September 2026- The 1.54 dry volume factor: the ratio of loose material to compacted concrete for a well-graded mix, and the standard figure for hand calculation
- Cement bulk density of 1440 kg/m³ and a 50 kg bag, which are what convert a volume share into a bag count
- Mix ratios of 1:2:4, 1:1.5:3 and 1:3:6 are the common ratios by volume, corresponding roughly to C20/25, C25/30 and C15 respectively
- Loose bulk densities of 1600 kg/m³ for sand and 1500 kg/m³ for aggregate, used only to convert cubic metres into tonnes for ordering
- The default price is dated in the pricing config and shown as an editable field, because it is the only number on this page that goes out of date
Assumptions used
- Dry aggregate bulks up: 1.54 m3 of loose dry material yields 1 m3 of compacted wet concrete. The figure is trade standard for a well-graded mix and covers the voids that the water and cement paste fill.
- Loose bulk density of Portland cement, which converts a volume share into bags.
- A workable structural mix without a plasticiser. Site conditions and admixtures change it, and the water figure is indicative only.
- Loose bulk densities, used only to convert cubic metres into tonnes for ordering.