Concrete Wall Calculator
Plan a poured concrete wall — foundation, basement, stem, or retaining. Get concrete volume (cubic yards, bags, truck loads), rebar quantities, formwork area, and a full cost breakdown with a downloadable PDF estimate.
Wall thickness, height, and reinforcement are structural and must follow your engineer and local code. Quantities are geometric estimates — verify before ordering. For planning purposes only.
| Thickness | Cubic Yards | 80 lb Bags | Truck Loads | Concrete Cost |
|---|
For your 240 sq ft net wall (waste included). Concrete cost = ready-mix only, at your $/cu yd.
How to use the concrete wall calculator
Four quick steps turn your wall dimensions into cubic yards, bag counts, rebar quantities, formwork area, and a full cost breakdown — whether you’re pouring a basement, stem, garage, or retaining wall.
Enter the wall size
Length × height in feet, wall thickness, any door/window openings to subtract, and how many identical walls — or tap a preset like Basement 30×8.
Add reinforcement & extras
Pick a rebar grid spacing for a both-ways layout, and tick waterproofing for below-grade faces. Leave them off for a plain pour.
Set waste, bag & prices
Allow 10%+ waste for tall forms, choose a bag size, and enter ready-mix, rebar, and optional labor prices for a live cost.
Read results & save a PDF
Get yards, feet, meters, bag counts, truck loads, rebar footage, formwork, and a thickness comparison — then download a PDF.
How wall volume is calculated
A wall is just its face area pushed back to its thickness. Multiply length by height for the face, subtract any openings, then multiply by the thickness in feet. Here is the exact math behind each output, all built from cubic feet.
Worked example — a 30 ft × 8 ft basement wall, 8″ thick
Face area: 30 × 8 = 240 sq ft
Volume: 240 × (8/12) = 160 cu ft
Cubic yards: 160 ÷ 27 = 5.93 cu yd
With 10% waste: 176 cu ft = 6.52 cu yd
Order about 6.5 cu yd ready-mix — one truck covers it.
Wall estimating charts
Handy lookups for the most common wall questions — concrete per square foot by thickness, typical wall jobs, rebar grid footage, and bag yields. Figures exclude waste, so add about 10% to your final order.
| Thickness | Cu ft per sq ft | Cu yd per 100 sq ft | 80 lb bags per 100 sq ft |
|---|---|---|---|
| 6 in | 0.50 ft³ | 1.85 yd³ | 84 bags |
| 8 in | 0.67 ft³ | 2.47 yd³ | 112 bags |
| 10 in | 0.83 ft³ | 3.09 yd³ | 139 bags |
| 12 in | 1.00 ft³ | 3.70 yd³ | 167 bags |
Multiply “cu ft per sq ft” by your net wall area (length × height minus openings). Bag counts are rounded up and exclude waste — above ~1 cu yd you’d order ready-mix, not bags.
| Job | Dimensions | Cubic feet | Cubic yards | 80 lb bags |
|---|---|---|---|---|
| Garage stem wall | 24 × 4 ft @ 8″ | 64 ft³ | 2.37 yd³ | 107 bags |
| Retaining wall | 20 × 4 ft @ 10″ | 66.7 ft³ | 2.47 yd³ | 112 bags |
| Basement wall (one side) | 30 × 8 ft @ 8″ | 160 ft³ | 5.93 yd³ | 267 bags |
| Tall foundation wall | 20 × 10 ft @ 10″ | 166.7 ft³ | 6.17 yd³ | 278 bags |
| Basement perimeter | 100 lf × 8 ft @ 8″ | 533 ft³ | 19.75 yd³ | 889 bags |
The bag column is shown for scale only. Every job here except the smallest is well over 1 cubic yard, where ready-mix is faster, cheaper, and gives a continuous pour. Bag counts exclude waste.
| Grid spacing | Vertical bars | Horizontal bars | Total linear ft (+10%) | 20 ft sticks |
|---|---|---|---|---|
| 12″ o.c. | 31 × 8 ft | 9 × 30 ft | 570 ft | 29 sticks |
| 16″ o.c. | 23 × 8 ft | 7 × 30 ft | 433 ft | 22 sticks |
| 18″ o.c. | 21 × 8 ft | 6 × 30 ft | 383 ft | 20 sticks |
| 24″ o.c. | 16 × 8 ft | 5 × 30 ft | 306 ft | 16 sticks |
Grid runs both ways: bars = (dimension ÷ spacing + 1) each way, plus 10% for laps. The calculator recomputes this for your exact length, height, and quantity. Bar size and spacing are structural decisions.
| Bag size | Yield | Bags per cu yd | Best for |
|---|---|---|---|
| 40 lb | 0.30 ft³ | 90 bags | Small repairs, easy lifting |
| 60 lb | 0.45 ft³ | 60 bags | Short stem & garden walls |
| 80 lb | 0.60 ft³ | 45 bags | Best value per ft³ |
Bag counts are always rounded up. For full-height walls, ready-mix almost always wins — bags suit sub-1-yard pours like short stem or garden walls.
Everything the calculator works out
One set of wall dimensions gives you every number needed to order and price the pour — from ready-mix trucks to rebar sticks to formwork panels.
Key figures every wall depends on
Built for any wall pour
From a short garden or garage stem wall to a full basement, the same calculator scales to the job.
Pouring a garage stem wall, a low retaining wall, or a garden wall and wants an exact order without over-buying.
- Start from a preset like Stem 40×4
- Subtract door/window openings
- Let it flag when bags beat ready-mix
Forming basement and foundation walls and needs cubic yards, rebar footage, and formwork area fast for a bid.
- Batch identical walls by quantity
- Size the rebar grid to spec
- Keep the PDF on file for quotes
Scoping a build with basement, stem, and retaining walls rolled into one materials and pour-day budget.
- Model each wall type separately
- Total the yards for pour-day trucks
- Use cubic meters for metric specs
7 tips for an accurate wall pour
Small habits keep your order right the first time and your wall straight, strong, and void-free.
Concrete wall calculator FAQ
The formulas, thickness guidance, rebar, and ordering questions people ask most before pouring a wall.
A poured wall is its face area times its thickness. Multiply length × height (in feet) for each wall, subtract any door and window openings, then multiply by the thickness in feet (inches ÷ 12). Divide total cubic feet by 27 for cubic yards.
Example: a 30 ft × 8 ft wall at 8″ thick = 240 sq ft × 0.667 = 160 cu ft = 5.9 cu yd. Add about 10% for waste on tall forms.
Use Volume = wall area × thickness, in matching units. Area = length(ft) × height(ft) × number of walls, minus openings. Convert thickness from inches to feet by dividing by 12.
Example: 40 ft × 4 ft at 8″ = 160 sq ft × (8/12) = 106.7 cu ft = 3.95 cu yd. Divide cubic feet by 27 for cubic yards, or multiply by 0.0283 for cubic meters.
Thickness is a structural decision set by load, height, and local code. As a rough guide, 6 to 8 inches is typical for residential foundation and basement walls, while 10 to 12 inches is common for tall walls and retaining walls that resist soil pressure.
Always confirm thickness, height, and reinforcement with your engineer and building department before pouring.
Rebar is usually placed as a grid both ways at a set spacing, commonly 12 to 18 inches on center for residential walls. For each wall, vertical bars ≈ (length ÷ spacing + 1) × height, and horizontal bars ≈ (height ÷ spacing + 1) × length. Add about 10% for laps and waste.
A 30 × 8 ft wall at 16″ o.c. needs roughly 430 linear feet, or about 22 twenty-foot sticks. Bar size and spacing are structural — follow your design.
Divide the total cubic feet by the bag yield: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft, 40 lb ≈ 0.30 cu ft.
A 30 × 8 ft wall at 8″ (160 cu ft) would take about 267 eighty-pound bags — which is why walls over roughly one cubic yard are almost always ready-mix, not bags. Reserve bags for small stem walls or repairs under a cubic yard.
Figure each wall as length × height × thickness. A single 30 ft × 8 ft basement wall at 8″ is about 5.9 cu yd. A full basement with roughly 100 linear feet of 8 ft wall at 8″ is around 20 cu yd — a multi-truck pour.
Because these volumes are far above one cubic yard, order ready-mix and plan one continuous pour to avoid cold joints.
Almost every full-height wall is ready-mix. Once you pass about one cubic yard — roughly 45 eighty-pound bags — bagged mix is hard to mix fast enough for a continuous pour, and ready-mix is cheaper and stronger as a monolithic wall.
Reserve bags for small stem walls, short garden walls, or patch work under a cubic yard. A concrete pump helps place tall walls.
Add about 10% or more for walls. Tall forms, pump and hose loss, form bulge, and uneven footings all consume extra concrete, and running short mid-pour creates a weak cold joint.
Round ready-mix up to the next quarter cubic yard. It’s cheaper to return a little concrete than to stop a wall pour halfway.
General Estimating Notice: This calculator provides geometric volume, rebar, formwork, and cost estimates based on user input and standard material yields. Actual quantities vary with form bulge, pump loss, and spillage, so order a little extra rather than running short. Wall thickness, height, and reinforcement are structural decisions — verify them with your local building code and engineer before ordering. For planning purposes only.