Concrete Block Calculator
Concrete Block Calculator
Landscape wall material estimator

Retaining Wall Block Calculator

Estimate wall blocks, cap blocks, compacted base gravel, drainage backfill, waste allowance, and optional material cost for segmental retaining wall projects.

Default sample is ready

Input

30 x 3 ft

Blocks

152

Gravel

4.44 cu yd

Includes cap blocks, a compacted gravel base, drainage backfill, and 10% waste. This is a planning estimate, not an engineered retaining wall design.

Edit the estimate Regular block wall

Estimate Retaining Wall Materials

Use this for landscape retaining wall blocks. For a straight CMU block wall, use the standard concrete block calculator instead.

Unit:

Wall Dimensions

Block & Cap Settings

Gravel Base & Backfill

Waste Allowance
10%

Use 5-10% for simple straight walls; increase for curves, cuts, or damaged blocks.

Cost Estimation

Enable to enter local block, cap, and gravel prices.

How This Retaining Wall Calculator Works

Retaining wall estimates are based on courses, not just total square footage. The calculator divides your wall height by the selected block height to estimate the number of courses, then divides wall length by block length to estimate blocks per course.

Base gravel and backfill are estimated as rectangular volumes. In imperial mode, the calculator converts cubic feet to cubic yards. In metric mode, it reports cubic meters.

The estimate is for material planning. Drainage, geogrid, footing depth, local code, surcharge loads, and engineering requirements vary by site.

Courses

ceil(wall height ÷ block height)

Rounds up so partial-height walls still include the next course of block.

Wall blocks

courses × ceil(length ÷ block length) × waste

Uses the selected retaining wall block face length, then applies the waste allowance.

Cap blocks

ceil(wall length ÷ cap length) × waste

Counts the top course separately because cap blocks usually use a different length than wall blocks.

Gravel

base volume + backfill volume

Base gravel uses length, base width, and base depth. Backfill uses length, wall height, and backfill depth.

Example Retaining Wall Estimate

The prefilled sample estimates a 30 x 3 ft segmental retaining wall with 6×16 Retaining Wall Block, cap blocks, a 10% waste allowance, a 2 ft base width, and 1 ft of drainage backfill.

Wall blocks

152

138 before waste

Cap blocks

33

top course estimate

Base gravel

1.11 cu yd

Backfill gravel

3.33 cu yd

Retaining Wall Estimate Checklist

Blocks and caps

Estimate regular wall blocks separately from top cap blocks, then add waste for cuts and breakage.

Base and backfill

Plan for a compacted gravel base and a drainage backfill zone behind the wall.

Drainage matters

Poor drainage is one of the most common retaining wall failure points. Material estimates do not replace drainage design.

Check wall limits

Tall walls, walls supporting driveways or structures, and code-regulated walls need professional review.

Frequently Asked Questions

How many retaining wall blocks do I need?
Divide the wall height by the block height to get the number of courses, then divide the wall length by the block length to get blocks per course. Multiply those two numbers and add a waste allowance.
Do retaining wall cap blocks count separately?
Yes. Cap blocks usually cover only the top course, so they should be estimated separately from the regular wall blocks. This calculator includes an optional cap block estimate.
How much gravel do I need for a retaining wall base?
Base gravel depends on the trench length, base width, and compacted base depth. Backfill gravel is estimated separately from the drainage zone behind the wall.
Can this calculator replace an engineer?
No. This is a material planning calculator for small landscape and segmental retaining wall estimates. Tall, load-bearing, terraced, or code-regulated walls should be reviewed by a qualified professional.