Cement Calculator
Estimate bags, component volumes, and waste for cement, sand, and stone with both US and metric units.
Project inputs
Slab, footing, column, or known volume measurements.
For slabs or footings, this is thickness. For columns, treat it as height.
Common sizes: 94 lb (US) or 25/50 kg (metric).
Use the bag label to confirm yield.
Typically 5–10% to cover spillage.
Advanced: density assumptions
How this cement calculator works
This calculator estimates how many bags of cement you need for concrete or mortar using volumetric mix ratios, density assumptions, and waste allowances that mirror professional take-offs.
- Supports slab, footing, column, or direct volume inputs.
- Lets you switch between US/imperial and metric units without recalculating by hand.
- Handles concrete (cement + sand + gravel) or mortar (cement + sand) mixes with custom ratios.
- Offers separate cement + aggregate outputs or premix bag counts for DIY mixes.
1. Calculate the total volume of concrete or mortar
Find the volume of the element you are casting. Choose slab, footing, or column geometry, or enter the known volume from engineering drawings.
Slab / pad (rectangle) — Volume = Length × Width × Thickness
Strip footing / trench — Volume = Length × Width × Depth
Cylindrical column / pier — Volume = π × (Diameter / 2)2 × Height
2. Apply the mix ratio
Mixes are specified by volumetric ratios such as 1 : 2 : 3 (cement : sand : gravel) or 1 : 4 (cement : sand) for mortar. The calculator prorates the total volume according to the ratio parts.
Let C = cement parts, S = sand parts, G = gravel parts, Vtotal = mix volume.
Total parts = C + S + G
Cement volume = Vtotal × C / (C + S + G)
Sand volume = Vtotal × S / (C + S + G)
Gravel volume = Vtotal × G / (C + S + G)
3. Convert cement volume to mass and bags
Multiply the cement volume by a bulk density to get mass, then divide by the cement bag weight. Add your waste allowance and round up to whole bags.
Cement mass: mcement = Vcement × ρcement
Raw bags: Braw = mcement / mbag
Final bags: Bfinal = ceil(Braw × (1 + waste%))
4. Premixed concrete bags
When using premixed bags, enter the total volume, yield per bag, and waste factor. The calculator shows how many bags to buy.
Premix bags (raw) = Vtotal / Vbag
Premix bags (final) = ceil(Vtotal / Vbag × (1 + waste%))
Typical mix ratios and when to use them
Concrete mixes (cement : sand : gravel)
- 1 : 2 : 3 – general-purpose concrete for slabs, footpaths, and driveways.
- 1 : 1.5 : 3 – higher-strength structural mixes (beams, columns), use only with engineered designs.
- 1 : 2.5 : 4 – leaner mixes for non-structural work.
Mortar mixes (cement : sand)
- 1 : 4 – general bricklaying mortar.
- 1 : 5 – lighter-duty masonry or plastering mortar.
Always follow local building codes and supplier recommendations for structural and load-bearing elements.
Practical tips for ordering cement
- Add 5–10% extra for waste, spillage, and uneven subgrades.
- Round up to the next full bag to avoid running out mid-pour.
- Check bag sizes – many regions use 25 kg or 50 kg bags instead of 94 lb.
- Consider ready-mix delivery for large volumes (roughly 3–4 m³ or 4–5 yd³ and up).
Frequently asked questions
How many 94 lb bags of cement are in 1 cubic yard of concrete?
For a 1:2:3 mix you usually need about 5.5–6 bags of 94 lb cement per cubic yard of concrete. This calculator gives a precise estimate accounting for your exact ratios and densities.
Can I change the mix ratio?
Yes. Adjust the cement, sand, and gravel ratio inputs. The calculator recomputes all component volumes and bag counts.
Is this calculator suitable for structural design?
No. This tool provides material estimates only. For structural elements (foundations, beams, columns), rely on a licensed engineer and local building codes.
About the author
Ugo Candido builds tools that explain how calculations work, focusing on transparent, practical models readers can trust. He reviews each calculator to ensure it matches how professionals think about the problem.
Contact: info@calcdomain.com
Editorial policy
CalcDomain content is educational, reviewed for clarity and accuracy, and avoids paid placements that would influence calculator outputs. Inputs and assumptions stay visible so you can verify how the results are produced.
Why use this calculator
- Avoid waste: precise material estimates prevent over-ordering.
- Dual mode: switch between detailed components and premix bags.
- Budget accurately: know cement, sand, and stone quantities before you quote.
- Supports all shapes: slabs, footings, or columns get the same attention.