Concrete Wall Calculator: Yards, Bags & ICF Blocks
Enter length, height and thickness to get cubic yards plus Quikrete-style 80 / 60 / 40 lb bag counts. An ICF section estimates block count from wall area and core-fill volume from core thickness. Sibling tools: concrete column, Sonotube, retaining wall blocks, CMU block, self-leveling concrete.
Quick answer
A 20 ft × 8 ft wall at 8 in thick needs 4.346 yd³ with 10% waste (106.667 ft³ exact) — about 196 × 80 lb bags (0.60 ft³ each), 261 × 60 lb, or 392 × 40 lb. With ICF forms (48×16 in face, 6 in core), the same wall faces about 33 ICF blocks and 3.259 yd³ of core fill with waste.
Updated 2026-10-28 · Uses Calcs.concreteWall. Bag yields match our Quikrete calculator. Method note: This page's method is a budgeting/volume model, not an industry standard.
How much concrete for my wall?
Length and height in feet; thickness in inches. Defaults: 20 ft × 8 ft × 8 in, 10% waste. Optional ICF: block face ft² (default 5.333 = 48×16 in) and core thickness.
Result
How do I use the concrete wall calculator?
- Measure the wall length (or centerline for a curve), the pour height, and the form thickness in inches.
- Set a waste percentage (10% is the page default for form bulge and chute cling).
- Optional: enter ICF block face area and core thickness to get block count and core-fill yards separately from a solid poured wall.
- Read cubic yards for ready-mix, or 80/60/40 lb bag counts for bagged mix.
Thickness sweep — 20 ft × 8 ft wall at 10% waste
Same footprint, five common thicknesses. Cells from Calcs.concreteWall(20,8,thickness,10). Bag yields: 80 lb = 0.60 ft³, 60 lb = 0.45 ft³, 40 lb = 0.30 ft³.
| Thickness | ft³ exact | yd³ w/ waste | 80 lb bags | 60 lb | 40 lb |
|---|---|---|---|---|---|
| 4 in | 53.333 | 2.173 | 98 | 131 | 196 |
| 6 in | 80.000 | 3.259 | 147 | 196 | 294 |
| 8 in | 106.667 | 4.346 | 196 | 261 | 392 |
| 10 in | 133.333 | 5.432 | 245 | 326 | 489 |
| 12 in | 160.000 | 6.519 | 294 | 392 | 587 |
Spot-check: 8 in row matches the quick-answer seed (106.667 ft³ → 4.346 yd³ → 196 × 80 lb).
Length sweep — 8 ft high × 8 in thick at 10% waste
| Length | Height | Thick | ft³ | yd³ w/ waste | 80 lb bags |
|---|---|---|---|---|---|
| 10 ft | 8 ft | 8 in | 53.333 | 2.173 | 98 |
| 16 ft | 8 ft | 8 in | 85.333 | 3.477 | 157 |
| 20 ft | 8 ft | 8 in | 106.667 | 4.346 | 196 |
| 24 ft | 8 ft | 8 in | 128.000 | 5.215 | 235 |
| 30 ft | 8 ft | 8 in | 160.000 | 6.519 | 294 |
| 40 ft | 8 ft | 8 in | 213.333 | 8.691 | 392 |
Worked examples (own arithmetic)
- Garden wall 12×4 ft × 4 in: 16.000 ft³ → 0.652 yd³ with 10% waste → 30 × 80 lb / 40 × 60 lb / 59 × 40 lb.
- Basement wall 40×8 ft × 6 in: 160.000 ft³ → 6.519 yd³ with waste → 294 × 80 lb bags. ICF (48×16 face, 6 in core): 66 blocks, 6.519 yd³ fill.
- Tall poured wall 30×9 ft × 10 in: 225.000 ft³ → 9.167 yd³ with waste → 413 × 80 lb. Not a structural design — volume only.
- Curved wall 25 ft centerline × 8 ft × 8 in: enter 25 as length → 133.333 ft³ → 5.432 yd³ with waste → 245 × 80 lb.
Method note: This page's method is a budgeting/volume model, not an industry standard.
ICF section — block count and core fill
Assumptions stated on this page (not a manufacturer schedule): block face 48 in × 16 in = 5.333 ft²; core thickness is the concrete cavity inside the forms. Fill volume uses core thickness, not the solid-wall thickness input. Blocks = ceil(area ÷ face × (1+waste%)).
| Wall L×H | Core | Area ft² | ICF blocks | Fill ft³ | Fill yd³ w/ waste | 80 lb bags (fill) |
|---|---|---|---|---|---|---|
| 20×8 ft | 6 in | 160.00 | 33 | 80.000 | 3.259 | 147 |
| 20×8 ft | 8 in | 160.00 | 33 | 106.667 | 4.346 | 196 |
| 40×8 ft | 6 in | 320.00 | 66 | 160.000 | 6.519 | 294 |
| 30×9 ft | 6 in | 270.00 | 56 | 135.000 | 5.500 | 248 |
Compare solid pour vs ICF fill on the same 20×8 footprint: solid 8 in wall is 4.346 yd³; 6 in ICF core is 3.259 yd³ — the difference is the foam form volume you are not pouring.
Formula & source
V(ft³) = L(ft) × H(ft) × t(in)/12; yd³ = ft³/27; bags = ceil(ft³×(1+waste%/100) / bag_yield). ICF blocks = ceil(L×H / face_ft² × (1+waste%/100)); ICF fill uses core thickness instead of solid t. Implemented as Calcs.concreteWall in this site's js/calcs.js. Bag yields align with Quikrete Concrete Mix data sheets (0.60 / 0.45 / 0.30 ft³).
FAQ
How much concrete for a 20×8 ft wall 8 inches thick?
A 20 ft long × 8 ft high × 8 in thick rectangular wall is 106.667 ft³ (3.951 yd³ exact). With 10% waste that is 4.346 yd³ — about 196 × 80 lb bags (0.60 ft³), 261 × 60 lb, or 392 × 40 lb.
What formula does this concrete wall calculator use?
Rectangular wall volume: V(ft³) = length_ft × height_ft × (thickness_in ÷ 12), then yd³ = ft³ ÷ 27. For a curved wall, enter the centerline length. This page calls Calcs.concreteWall from this site's own js/calcs.js.
How many Quikrete bags for a concrete wall?
Divide volume-with-waste by bag yield: 80 lb Concrete Mix ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 40 lb ≈ 0.30 ft³ (manufacturer data sheets, same as our Quikrete calculator). The 20×8×8 in seed wall needs 196 × 80 lb bags at 10% waste.
How do I estimate ICF blocks for a wall?
This page's ICF section uses a stated face of 48 in × 16 in (5.333 ft² per block) and a user-chosen core thickness for fill volume. Blocks = ceil(wall area ÷ face × (1+waste%)). A 20×8 ft wall at 10% waste needs 33 blocks; 6 in core fill is 3.259 yd³ with waste.
Is this an engineering design for a retaining wall?
No. This is a budgeting/volume model for poured or ICF walls. Reinforcement, soil pressure, drainage, and frost depth follow your local code and a licensed engineer — not this calculator.
Concrete wall vs retaining-wall block calculator — which page?
Use this page for poured concrete or ICF fill volume and bags. For dry-stack or mortar-set CMU/landscape block counts and base gravel, use the retaining wall block calculator instead.
Should I add waste when ordering for walls?
Yes. 5–10% covers form bulge, over-excavation, and chute cling. This calculator defaults to 10%. Ready-mix short-load fees often dominate small wall orders.