Use our retaining wall calculator to determine how many blocks you’ll need to purchase. We’ll also walk you through taking measurements and manually calculating the number of blocks needed.
Retaining Wall Calculator
Enter the dimensions of the wall and blocks:
Retaining Wall Calculator
To calculate how many blocks for a retaining wall, enter the height and length of your wall dimensions and the height and length of each block.
How to Calculate How Many Blocks for a Retaining Wall
Calculate the total surface area to determine the number of blocks you need for a retaining wall. To do this, multiply the length x the height of the wall in feet – the total is the wall’s square footage.
Square footage of the wall = length x width in feet
Now determine the square footage of the outside face of each block by multiplying the length times height in inches. Then, divide that total by 144.
Face square footage of each block = length x height in inches ÷ 144
Finally, divide the square footage of the wall by the square footage of the block to determine how many you need.
Retaining wall blocks needed = wall square footage ÷ individual block square footage
For example, if your retaining wall is 10 feet long by 3 feet tall, it’s 30 square feet (10 x 3). If your blocks are 16 inches long and 10 inches high, they’re equivalent to 1.11 square feet per block. Therefore you’d need about 28 blocks for your wall.
How Much Extra Blocks Should You Buy for a Retaining Wall?
When taking on any construction project, you must account for waste. You may need to cut blocks, rendering some portions unusable. Plus, there’s a chance of accidental damage. And since a portion of the first row of retaining blocks may be partially underground for stability, having extra allows you to reach your desired height. We recommend adding a 12 to 15% waste factor for retaining wall blocks.
To add a 12% waste factor, multiply the number of blocks you need by 1.12.
To add a 15% waste factor, multiply the number of blocks you need by 1.15.
How to Figure How Many Cap Blocks for a Retaining Wall
A retaining wall cap block is the top piece of the wall, often serving a decorative purpose, giving your wall a finished look. To determine how many cap blocks you’ll need, determine what size you’ll use.
Once you know the length of your cap block in inches, measure the length of the retaining wall and convert that to inches. (If you took your measurement in feet, multiply the number of feet by 12 to determine the total amount of inches.)
Now divide the retaining wall length by the cap block length – that’s the number of cap blocks you need.
Here’s an example:
For this example, we’ll pretend you’re using a 16” retaining wall cap block, and your retaining wall is 144” long. Since 144 divided by 16 is 9, that’s the number of cap blocks you’ll need.
Frequently Asked Questions (FAQ)FAQ
How do I figure out what retaining wall blocks will cost?
Once you’ve determined how many blocks you need by dividing the wall’s surface area by the block’s outside face area, multiply that number by the price per block. For example, if you need 120 blocks and each block is $5.48, the cost of the blocks will be $657.60.
How many cinder blocks do I need for a retaining wall?
The average cinder block dimensions are 16 x 8 x 8. That means the square footage of the outside face is 0.89 square feet. Now determine the square footage of your retaining wall by multiplying the length x width in feet. Then divide that number by 0.89 to calculate how many cinder blocks you’ll need.
How much of a retaining wall should I bury?
An accepted rule of thumb is to bury 1/8th of the height of the wall. So, for a four-foot wall, you’d bury about 6 inches.