Retaining Wall Calculator
Count blocks, caps and gravel, including the buried course. This retaining wall calculator adds your labor and margin to build a clearer job estimate.
Measure your wall
Why this number
Excludes cap thickness. Whole courses may make the built wall slightly taller.
Why this number
Use the project specification. Added to exposed height before rounding courses.
Your materials and work rates
Illustrative starting numbers, not local market averages. Replace them with supplier quotes and your own work speeds.
Why this number
Zero for solid units. Use the maker's cavity fill volume for hollow units.
Why this number
Added to geometric volume, then rounded up to a quarter yard. Confirm compaction and ordering units with your supplier.
Why this number
Include excavation, base placement and compaction for your actual site.
Why this number
Include block setting, backfill, core filling, drainage and caps. Extra time belongs in the labor allowance.
Labor, overhead and profit
Why this number
Include labor not covered by the production rates, such as gates, disposal or drainage outlets.
Why this number
Your cost per person-hour, including payroll burden. Not your billing rate.
Why this number
Delivery, disposal, gate assemblies, permits, engineering or other materials. Add their labor separately.
Why this number
Price = cost / (1 - margin). Must be below 100%.
Estimated job price
$3,375
30.0% actual margin. Before sales tax. Rounded up to $5.
| Courses incl. buried block | 5 courses |
| Blocks per course | 30 blocks |
| Blocks to order | 158 blocks |
| Caps to order | 32 caps |
| Base stone (net) | 1.48 yd³ |
| Drainage stone (net) | 3.7 yd³ |
| Core fill (net) | 0 yd³ |
| Total stone to order | 5.75 yd³ |
| Toe drain allowance | 40 ft |
| Built height above grade, before caps | 2 ft |
Your cost breakdown
- Trench and base
- 4.00 person-hr
- Installation
- 12.50 person-hr
- Labor incl. extra time
- $648
- Equipment + extra costs
- $150
- Overhead
- $215
- Profit
- $1,014
Quantity and budget estimate only. Use your wall system and site design for embedment, base, drainage and reinforcement. This tool does not establish a safe wall height.
Straight, level-base, uniform-height wall. Curves, corners, steps and terraces need a separate layout. Cap thickness is additional to the entered exposed block height.
Add excavation/disposal beyond the trench allowance, drainage outlets, geogrid, fabric, adhesive, delivery, permits and engineering to extra costs and labor as needed.
Core fill is set to zero for solid blocks. Enter the manufacturer's cavity volume for hollow blocks.
How does the retaining wall block calculator work?
Count blocks per course from wall length and block face length. Count courses from exposed height plus buried depth. Round both up before multiplying, then add waste. This gives a purchase estimate for a straight, uniform-height wall. Caps are counted separately, and their thickness is extra to the entered height.
Blocks = round up(length ÷ block length) × round up(total block height ÷ block height). Apply your cutting allowance after counting the installed blocks.
Use inches consistently when dividing. Allan Block's material worksheet also includes buried block in the wall height. For poured work elsewhere on site, use the concrete quantity calculator.
Keep base stone, drainage stone and core fill separate
Base stone supports the wall, drainage stone sits behind it, and core fill belongs inside hollow units. Calculate each volume separately to avoid missing a zone or counting one twice. The calculator assumes these zones don't overlap and prices them with one stone rate; adjust for your specification.
| Material | Quantity formula | Check before ordering |
|---|---|---|
| Base stone | Length × base width × base depth ÷ 27 | All dimensions in feet; width includes the block footprint |
| Drainage stone | Length × stone-zone width × built height ÷ 27 | Width is behind the block, not through it |
| Core fill | Installed blocks × cavity volume per block ÷ 27 | Cavity volume in cubic feet; zero only for solid units |
| Caps | Round up(length ÷ cap length), plus allowance | End details, curves and cuts |
Allan Block's water-management guidance distinguishes incidental wall drainage from wider site runoff. This calculator includes a toe-drain length allowance, but it doesn't design outlets or solve a drainage problem.
A 40-foot retaining wall estimate, worked through
This hypothetical straight wall has 2 feet of exposed block plus 6 inches buried. Blocks are 16 inches long, 6 inches high and 12 inches deep, with 16-inch caps. It uses solid units, a 24-inch-wide by 6-inch-deep base and a 12-inch drainage zone. Confirm your design rather than copying these dimensions.
| Line | Example |
|---|---|
| Installed blocks | 30 per course × 5 courses = 150 |
| Order with 5% allowance | 158 blocks, 32 caps |
| Net stone | 1.48 yd³ base + 3.70 yd³ drainage |
| Stone order | 5.75 yd³ after 10% allowance and quarter-yard rounding |
| Materials | $1,349 |
| Labor | 4 hours trench/base + 12.5 installation + 2 extra = 18.5 person-hours |
| Loaded labor | 18.5 × $35 = $647.50 |
| Equipment | $150 |
| Overhead | 10% × $2,146.50 = $214.65 |
| Total cost | $2,361.15 |
| Price at 30% target margin | $3,375, rounded up to $5 |
Example material prices are $4 per block, $6 per cap, $60 per yard of stone, $2 per foot of drain pipe and $100 for fittings. These are editable budget numbers, not a local quote. Hollow units need core fill added, and supplier minimums may change your order.
What belongs in a retaining wall cost estimate?
Include site preparation, materials, installation, delivery, equipment, disposal and overhead before adding profit. The job margin calculator can help check your pricing. Extra excavation, reinforcement and access problems can change the scope substantially.
- Confirm the wall system, site design and local approval requirements.
- Measure lengths and heights, splitting any stepped or varying-height layout into a separate takeoff.
- Replace block dimensions, cavity fill and stone zones with the specified values.
- Price delivery, outlets, geogrid, fabric, adhesive, disposal and additional labor.
This is a quantity estimate, not a wall design or a statement that a given height is safe. Once the scope is confirmed, organize the estimate with WinPal for landscaping businesses, or choose another tool from the calculator library.
Common questions about the retaining wall calculator
How many retaining wall blocks do I need?
Round wall length divided by block face length up to whole blocks per course. Round exposed height plus buried depth up to whole courses, then multiply. Add a cutting and breakage allowance. Use the actual face dimensions of your block; mixed-size systems need their manufacturer's pattern takeoff.
Does wall height include the buried course?
Enter exposed block height and buried depth separately. The calculator adds them before counting courses, then shows the resulting above-ground height. Caps sit above that height. If your design specifies a finished top elevation, subtract the cap thickness when entering the exposed block height.
How much gravel goes behind a retaining wall?
The quantity is wall length times the specified drainage-stone width times the built block height, converted to cubic yards. Base stone and hollow-block core fill are separate quantities. Their total receives your ordering allowance. Drainage dimensions and discharge paths must come from the wall system and site design.
Can this retaining wall calculator tell me whether I need geogrid?
No. It estimates quantities and costs, not stability or reinforcement. Soil, slope, water, nearby loads and the wall system affect the design. Have the appropriate professional and local authority confirm requirements. Add specified geogrid, engineering and installation costs to the estimate before using it as a quote.
Can I use it for curved walls or concrete retaining walls?
This version covers a straight segmental block wall with a level base and uniform height. Curves, corners, steps and terraces change the layout and quantities. Poured concrete walls also need forms, reinforcing and a structural design. The concrete calculator can help with a separately specified concrete volume.
Turn the numbers into your next estimate.
Use your reviewed quantities and rates to create an estimate in WinPal.