Wall Concrete Calculator
Wall concrete = length × height × thickness, minus openings. A 40 ft foundation wall 8 ft high and 8 in thick, with a 6 ft² window opening, needs 7.75 yd³ — about 8.5 yd³ with 10% waste, weighing roughly 15.7 tons. For the footing below, use the Concrete Footing Calculator.
How it's calculated: Volume = (length × height − openings) × thickness; weight = volume × 150 lb/ft³; bags = volume ÷ bag yield.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Volume = length × height × thickness − (opening area × thickness)
Weight = volume × 2,400 kg/m³ (150 lb/ft³)
Bags = volume ÷ bag yield (40 lb → 0.30 ft³, 60 lb → 0.45, 80 lb → 0.60)
Run the calculation to see each step with your own numbers.
A 40 ft × 8 ft foundation wall, 8 in thick, one 3×2 ft window well opening (6 ft²), ready-mix, 10% waste.
Gross = 40 × 8 × 0.667 = 213 ft³ = 7.9 yd³
− openings 6 × 0.667 = 4 ft³ → 7.75 yd³
Order with 10% ≈ 8.5 yd³; weight ≈ 15.68 tons (17.25 tons with 10%)
- Rectangular wall of constant thickness. A tapered (battered) retaining wall — use the average thickness.
- Openings are deducted as their face area × wall thickness. Rebar, water and air are not deducted (negligible).
- This is the wall stem only — footings, keys, pilasters and a slab are separate.
- Retaining walls need engineered reinforcement and drainage — this calculator sizes the pour, not the design.
- Bags or ready-mix for a wall?
- It depends on the volume and your supplier's minimum order and fees. One cubic yard is 45 bags of 80 lb mix at a 0.60 ft³ yield (Quikrete Concrete Mix 1101; Sakrete High-Strength Concrete Mix), so the 40 × 8 ft × 8 in example wall, about 7.9 yd³, would take about 356 bags. Compare that with a ready-mix quote.
- How do I handle a tapered retaining wall?
- Enter the average thickness — halfway between the thick base and the thin top. The small error either side cancels out and the waste allowance covers the rest.
- Is the rebar deducted from the volume?
- No. Steel, water and entrained air displace a negligible fraction of a wall pour, so the calculator ignores them.
- How much concrete do I need for a foundation wall?
- Multiply length × height × thickness in feet and divide by 27 for cubic yards. A 40 × 8 ft wall 8 in thick is 213 ft³ (7.9 yd³) before openings and the 10% waste allowance.
- How thick is a poured concrete wall?
- Common poured walls are 8, 10 or 12 in thick; the thickness comes from your drawings or local code, not from this calculator. Each extra 2 in on a 40 × 8 ft wall adds about 53 ft³ (2 yd³).
Geometry
Rectangular-prism volume. Unit conversions per NIST SP 811.
Concrete density
2400 kg/m³ — Normal-weight fresh concrete ≈ 2,400 kg/m³ (≈150 lb/ft³). Portland Cement Association (PCA), 'Design and Control of Concrete Mixtures' (EB001).
Bag yields
80 lb pre-mix ≈ 0.60 ft³ yield. Quikrete Concrete Mix 1101; Sakrete High-Strength Concrete Mix.
About the Wall Concrete Calculator
The Wall Concrete Calculator gives the concrete volume, weight and (if you are bagging it) bag count for a poured wall — a foundation stem or a retaining wall — from the length, height and thickness, with openings deducted. It sizes the pour, not the design: a retaining wall still needs engineered reinforcement and drainage. Footings, keys and pilasters are separate.
What you enter
- Wall length
- Wall height
- Wall thickness — Common poured walls are 8, 10 or 12 in.
- Opening area to deduct — Total face area of windows, doors and beam pockets.
- If bagging it: bag size
- Waste allowance — Default 10%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Concrete volume — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Concrete weight — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Bags for the net volume (if bagging) — 0 for a ready-mix truck. Exact = bags for the exact volume; recommended = whole bags including the waste allowance. One cubic yard (27 ft³) is 45 bags of 80 lb or 60 bags of 60 lb at the stated yields — compare that with a ready-mix quote.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Concrete Calculator — How much concrete a rectangular slab or footing needs, in cubic yards or cubic metres.
- Concrete Footing Calculator — Concrete volume for strip and pad footings.
- Retaining Wall Calculator — Block count and base material for a segmental retaining wall.
- Concrete Cost Calculator — Estimated material cost of a concrete pour from its volume and a unit price.
- Concrete Weight Calculator — Weight of a concrete volume, for transport and load planning.
Part of the Walls calculators.