Retaining wall block calculator
Count the segmental blocks a retaining wall needs from its length and height, with an optional cap block row.
Retaining wall block calculator
Count the segmental blocks a retaining wall needs from its length and height, with an optional cap block row.
Enter wall length and height to estimate the blocks you need.
Blocks needed
Project summary
How it works
Estimate only. This is a straight vertical block count; base gravel, drainage, geogrid and setback for battered walls are not included. Check the manufacturer installation guide and local code before ordering.
Retaining wall block calculator
Height sets the courses, length sets the blocks per course
The wall is built up in courses, or rows, so the wall height divided by the block height gives the number of courses needed. Each course then runs the length of the wall, so the wall length divided by the block width gives the blocks needed to fill one course. Multiplying the two gives the structural block count, and an optional cap row adds one more row of a typically flatter cap unit along the top.
A straight count, not a full wall design
This calculator counts blocks for a straight vertical wall face. It does not account for setback, the slight backward step each course of a battered wall takes from the one below it, which shortens the effective length of the upper courses, nor does it include the base gravel, drainage and geogrid a real segmental wall needs, especially above a couple of feet. Check the block manufacturer installation guide and local code for those requirements before ordering.
Frequently asked questions
How many blocks does a 20 foot long, 24 inch tall retaining wall need?
With a typical 6 inch block height and 18 inch block width, a 24 inch tall wall needs 4 courses, and a 20 foot long wall needs 14 blocks per course, for 56 structural blocks before waste. Enter your own wall dimensions above for the exact count.
Does this include base gravel and drainage?
No. This calculator counts the wall blocks only. A real retaining wall installation also needs a compacted gravel base, drainage behind the wall, and often geogrid reinforcement for taller walls. Follow the block manufacturer installation guide and check local code for those requirements.
How many blocks do I need for a 50 foot long wall?
Standard blocks are 12 inches long. For a 50 foot wall, you need about 50 blocks per course. The calculator gives you the total based on your wall dimensions and block size.
How many courses do I need for a 3 foot wall?
Standard blocks are 6 inches tall per course. A 3 foot wall needs 6 courses. The calculator multiplies courses by the number of blocks per course.
Do I need gravel behind a retaining wall?
Yes, a gravel backfill behind the wall provides drainage and reduces hydrostatic pressure. Use 6 to 12 inches of clean gravel. The calculator estimates blocks, and you plan backfill separately.
How deep should a retaining wall footing be?
The first course should be buried at least 6 inches below grade. Taller walls need engineered footings. The calculator counts blocks, and your engineer specifies footing requirements.
How much does a retaining wall cost per foot?
Material costs range from 10 to 30 dollars per square foot of wall face depending on block type. The calculator gives you the square footage for pricing.
Can I build a retaining wall myself?
Walls under 3 feet are generally manageable for a skilled DIYer. Taller walls require engineering and permits. The calculator counts blocks for any height, and you decide whether to hire a professional.