How it works
The calculator takes the face area of the wall, subtracts the openings, multiplies by the thickness and adds your extra allowance.
Wall face area = Length × Height − Σ (Opening width × Opening height × Count)
Volume = Wall face area × Thickness
Concrete to order = Volume × (1 + Extra ÷ 100)
Bags = ⌈ Concrete to order ÷ Yield per bag ⌉
⌈ ⌉ means rounding up to the next whole bag. The volume itself is not rounded.
Units are converted internally, so you can enter the length in feet and the thickness in inches; the result is shown in cubic yards and cubic feet (or cubic meters and liters). The default yield of 0.60 cu ft is QUIKRETE’s figure for an 80 lb bag of its Concrete Mix – change it to match your bag. This tool estimates material quantity only; wall size and reinforcement come from your plans and local code.
Worked example
Inputs
- Wall length
- 20 ft
- Wall height
- 4 ft
- Wall thickness
- 8 in
- Yield per bag
- 0.6 cu ft
- Extra concrete
- 0 %
Result
- Concrete to order
- 1.98 cu yd (53.33 cu ft)
- Bags
- 89
- Wall face area
- 80 sq ft
- Volume before extra
- 1.98 cu yd (53.33 cu ft)
Common mistakes
- Measuring the outside of the forms, or the length of a corner wall twice. At a corner, count the overlap once – for example, take the full length of one wall and the other wall less one thickness.
- Entering the thickness in feet instead of inches. An 8 in wall is two thirds of a foot; typing “8 ft” makes the order twelve times too large.
- Leaving out the footing below the wall. It is a separate pour with its own size; calculate it with the concrete footing calculator.
- Subtracting openings that will be filled with concrete later, or forgetting the ones that will not.
- Taking wall thickness, height or reinforcement from a calculator. Those come from your plans, local code or a qualified professional.
Assumptions and limits
- The wall is straight with the same thickness over its full length and height. Battered faces, pilasters, brick ledges and bulkheads are not modeled.
- Openings are rectangles through the full thickness of the wall.
- The volume of rebar, ties or embedded items is not subtracted, and the footing is not included.
- Bags are rounded up to whole bags after the extra allowance. Without a yield, only the volume is shown.
- This is a material quantity only, not a structural design.
Frequently asked questions
How do I calculate the concrete for a wall?
Multiply the length by the height and the thickness, then subtract any openings. A wall 20 ft long, 4 ft high and 8 in thick is 20 × 4 × 0.667 ≈ 53.3 cu ft, or about 1.98 cu yd (divide cubic feet by 27).
How many bags of concrete do I need for a wall?
Divide the volume by the yield printed on the bag and round up. QUIKRETE’s data sheet lists about 0.60 cu ft for an 80 lb bag of its Concrete Mix, so the 53.3 cu ft wall above needs 89 bags before any extra.
Should a basement wall be poured from bags?
Full-height walls usually need several cubic yards placed in one continuous pour, which is why they are normally poured with ready-mix. Use the volume here to ask suppliers for a quote.
How thick should a concrete wall be?
That depends on its height, the soil it holds back, the load on it and local code. This calculator doesn’t recommend a thickness – use your plans or ask a qualified professional.
Sources
- QUIKRETE Concrete Mix (No. 1101) Product Data Sheet — The QUIKRETE Companies. Yield per bag: 40 lb ≈ 0.30 ft³, 50 lb ≈ 0.375 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³, 90 lb ≈ 0.675 ft³.
- 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 4, 2026