Retaining Wall Calculator

Calculate the number of blocks and gravel needed for a retaining wall.

Use decimals when needed. This estimate updates live and is safe to tweak before you buy materials.

Estimated blocks

Retaining Wall Buying Guide

This guide helps you turn your retaining wall calculator result into a cleaner purchase plan. Use it when you want fewer return trips, better waste assumptions, and a more realistic cart.

Step 1: Account for the buried course

A retaining wall needs a solid foundation. You must bury the entire first course of blocks below ground level. Add this buried height to your visible wall height.

Step 2: Calculate the setback

Segmental blocks are designed to step back slightly into the hill as they go up. A tall wall will lean back significantly, requiring more backfill gravel.

Step 3: Cap it off

Standard blocks look unfinished on top. You must buy specialized capstones, which are sold by linear foot rather than square foot, to finish the top row.

Recommended for this job

Commonly paired tools and accessories

These are the practical extras people often forget until the last minute, especially when turning a rough estimate into a real purchase list.

Heavy duty construction adhesive preview

Heavy duty construction adhesivevia Amazon.comWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.

Landscape fabricvia Amazon.comWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.

Disclosure: these may be affiliate links.

Retaining wall cost planning rule of thumb

The blocks are only part of the expense. You need tons of drainage gravel (3/4-inch clean stone), perforated drain pipe, landscape fabric, and masonry adhesive.

Understanding the Math

Formula: The basic formula for Retaining Wall Calculator typically involves calculating the total area or volume (Length × Width × Depth) and dividing by the coverage of a single unit or package, then adding a waste factor (usually 10%).

Example: For example, if you have a 10x10 area and your material covers 10 square feet per unit, you need 10 units. With a 10% waste factor, you should purchase 11 units to ensure you don't run short.