Concrete Wall Calculator
Concrete volume and bag count for poured foundation, retaining, and basement walls. Pick an application preset for typical sizes, or enter your own dimensions. For CMU or cinder block walls, use the Concrete Block Calculator.
Results
Estimates only. Verify dimensions on site, follow local building code for thickness and reinforcement, and have retaining walls over 4 ft engineered. TakeoffCalc isn't responsible for material over- or under-orders.
How to use this calculator
- 01Pick an Application preset to fill typical dimensions, or leave it on Custom to enter your own. Presets cover the most common cases: foundation perimeter, single foundation wall, residential and heavy retaining, and basement.
- 02Choose a Wall Type. Foundation runs under structures. Retaining holds back soil. Basement is typically thicker for backfill pressure. The math is the same for all four. Type affects the reference context, not the formula.
- 03Enter Length and Height in feet (or meters), plus Thickness in inches (or centimeters). For multi-wall projects (perimeters, sectioned retaining), set Number of Walls. The calculator returns the project total in one shot.
- 04Pick your Bag Size and Waste Factor. 80-lb (36-kg) bags are standard for walls. 10% waste covers the partial-bag overage that can’t be returned. For projects over ~1 cubic yard (0.76 m³), ready-mix delivery is usually cheaper than bags.
- 05Read the results. Total Concrete Needed includes waste and is the orderable cubic yardage. Total Bags is computed from total volume directly, so it can be slightly less than per-wall bags multiplied by the count. That’s normal and reflects actual minimum demand.
Understanding the math
Every poured wall is a rectangular volume: length × height × thickness. Length and height are given in feet. Thickness comes in inches and needs to be converted:
volume ft³ = (lengthFt × heightFt × thicknessIn) / 12 · yards = ft³ / 27 metric: volume m³ = lengthM × heightM × thicknessM (all in meters)
For multi-wall projects, multiply the per-wall volume by the count to get total cubic feet. Total bag count is computed from total volume directly, not by multiplying per-wall bags by the count. That single ceiling step gives the actual minimum bag demand, which can be slightly lower because per-wall rounding inflates each wall independently.
Worked example: a 30-foot foundation wall at 8 feet tall × 8 inches thick (9 m × 2.4 m × 20 cm), single wall, 80-lb (36-kg) bags, 10% waste. Volume = (30 × 8 × 8) / 12 = 160 cubic feet (4.53 m³), or 5.93 cubic yards (4.53 m³). With 10% waste: 6.52 cubic yards (4.99 m³). Bags = 160 × 1.10 / 0.6 = 293.33, rounded up to 294 bags. Weight = 160 × 150 = 24,000 lbs (10,890 kg). A typical 4-wall perimeter at the same dimensions: 640 cubic feet (18.12 m³), 26.07 cubic yards (19.93 m³) with waste, 1,174 bags, 96,000 lbs (43,545 kg).
Wall reference chart
Volume and 80-lb bag count for typical poured concrete walls. Volumes shown without waste; bag counts include 10% waste so they match the calculator’s default output.
| Application | Dimensions | Volume | 80-lb Bags |
|---|---|---|---|
| Foundation wall (typical home) | 30 ft × 8 ft × 8″ | 5.93 yd³ | 294 |
| Foundation perimeter (4 walls) | 4× (30 × 8 × 8″) | 23.70 yd³ | 1,174 |
| Retaining wall (residential) | 20 ft × 4 ft × 10″ | 2.47 yd³ | 123 |
| Retaining wall (heavy) | 30 ft × 6 ft × 12″ | 6.67 yd³ | 330 |
| Basement wall (typical) | 30 ft × 8 ft × 10″ | 7.41 yd³ | 367 |
| Garage stem wall | 24 ft × 3 ft × 8″ | 1.78 yd³ | 88 |
| Garden retaining wall (low) | 15 ft × 3 ft × 8″ | 1.11 yd³ | 55 |
Frequently asked questions
How much concrete do I need for a wall?
A wall is a rectangular volume: length × height × thickness. Multiply all three in feet, then divide by 27 to convert cubic feet to cubic yards. The catch is thickness, usually given in inches but the formula needs feet. For a 30-foot wall at 8 feet tall × 8 inches thick (9 m × 2.4 m × 20 cm): 30 × 8 × 0.667 = 160 cubic feet (4.53 m³). That works out to 5.93 cubic yards (4.53 m³). Add 5-10% waste because concrete is wet. Partial trucks can't be returned. The calculator above handles unit conversion and waste.
How thick should a foundation wall be?
Standard residential foundation walls are 8 inches (20 cm) thick for 1-story homes and 10 inches (25 cm) for 2-story homes. Basement walls deeper than 7 feet (2.1 m) may need 10-12 inches (25-30 cm). Garage stem walls and shed footings are typically 6-8 inches (15-20 cm). Verify with local building codes. Wall thickness depends on soil type, backfill height, and structural load. Engineers may specify thicker walls for poor soils or seismic zones.
How tall can a residential retaining wall be without engineering?
Many jurisdictions use about 4 feet (1.2 m) as a common trigger for engineering or permits, but the actual limit varies. Slopes, surcharge loads, poor drainage, weak soils, or nearby structures can require engineering at lower heights. Check local code and project requirements before pouring.
What is the difference between poured concrete and block walls?
Poured walls are continuous concrete, formed and poured as a single monolithic structure. Block walls are made of individual concrete masonry units (CMU) stacked with mortar joints, often filled with grout for reinforcement. Poured walls are stronger and more waterproof, common for foundations and basements. Block walls are easier for DIY and don't require concrete trucks. For block wall calculations, use the Concrete Block Calculator. This calculator handles poured walls only.
Do concrete walls need rebar?
Structural poured walls commonly need reinforcement, but exact bar size, spacing, horizontal steel, cover, and placement depend on wall height, soil pressure, loads, local code, and project plans. Short decorative or non-structural walls may have different requirements. Check local code or a qualified professional before pouring.
How do I calculate concrete for a curved or circular wall?
Curved walls use a different formula. For a full circle: π × outer radius² minus π × inner radius² × height = volume. For a curved wall section, calculate as a partial cylinder shell or break into straight segments. The calculator above handles straight rectangular walls only. For curved walls, segment your wall into straight runs and calculate each separately, then add the volumes together. For complex circular structures, consult an engineer or a detailed concrete calculator that handles cylindrical math.
Can I use this calculator with metric measurements?
Yes. Switch the unit selector to Metric and the inputs, bag options, results, reference values, and examples update to metric units where applicable.
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