How to calculate retaining wall blocks
The calculator divides the exposed wall height by the block face height to estimate the number of visible courses. It then adds any full buried base courses entered.
Wall length is divided by the block face length to estimate blocks per course.
The selected waste percentage is then added and the result is rounded upward to whole blocks.
Retaining wall example
Suppose a retaining wall is 30 feet long and has an exposed height of 3 feet. Using blocks with a 12-inch face length and 6-inch face height gives six exposed courses.
If one additional course is buried, the wall has seven total courses. A 30-foot wall requires 30 blocks per course, giving 210 blocks before waste.
Adding 5% waste gives an estimate of 221 wall blocks to buy.
What are buried base courses?
Retaining walls often begin with part of the wall below the visible finished grade. This calculator lets you add full buried block courses separately from the exposed wall height.
The calculator does not determine how many courses should be buried. Required embedment depends on the wall system, block manufacturer, grade, soil and project design. Enter the number specified for your project.
Calculating cap blocks
If the wall will use a cap row, enter the actual cap face length. The calculator divides the wall length by the cap length and applies the same waste allowance.
Cap blocks can differ in size from the wall units, so their length is entered separately.
Why include waste?
Retaining wall projects can require extra blocks because of cuts, damaged units, corners, curves, layout adjustments and other job-site losses.
The waste percentage is adjustable and is applied separately to wall blocks and cap blocks.
Straight walls, curves and corners
The basic calculation assumes the entered wall length can be represented using the selected block face length. Curves, corners, setbacks and special units can change the actual quantity required.
Manufacturer layout guidance should be used when a wall contains significant curves, corners or special block types.
Retaining wall blocks vs. concrete blocks
Segmental retaining wall units are commonly laid in horizontal courses and may include setback features, lips, pins or other system-specific geometry.
For an ordinary masonry wall, use the Concrete Block Calculator. For a poured concrete wall, use the Concrete Wall Calculator.
What this calculator does not design
This calculator estimates block quantity only. It does not determine allowable wall height, footing or base preparation, drainage, backfill, setback, geogrid, reinforcement, soil pressure, surcharge loads or structural stability.
Follow the block manufacturer's instructions, project drawings and applicable requirements.
Frequently asked questions
How many retaining wall blocks do I need?
Divide the wall height by block height to find courses, divide wall length by block length to find blocks per course, then multiply the two values and add waste.
Does the calculator include buried blocks?
Yes. Enter the number of full buried base courses separately from the exposed wall height.
Can I calculate cap blocks?
Yes. Enable the cap row and enter the actual cap face length.
Does waste apply to cap blocks too?
Yes. The selected waste allowance is applied to both wall blocks and cap blocks.
Can this calculator design a retaining wall?
No. It estimates material quantity only. Wall design and stability depend on site conditions, wall system and engineering requirements.
Using this calculator effectively
The Retaining Wall Block Calculator estimates wall blocks from wall length, exposed height, block face dimensions and buried base courses. It can also estimate cap blocks, waste allowance and optional material cost.
Common uses
- Estimating segmental retaining wall blocks before ordering materials.
- Including full buried base courses in addition to the visible wall height.
- Estimating an optional cap row separately when cap units have a different face length.
Tips for a better estimate
- Use the actual block face length and height for the retaining wall product being installed.
- Enter buried courses from the project or manufacturer requirements rather than assuming a universal embedment depth.
- Allow for curves, corners, cuts and special units because they can change the quantity from a simple straight-wall estimate.
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