Retaining Wall Block Calculator

Calculate the exact number of blocks needed for your retaining wall project. Enter your wall dimensions and select your block size to get accurate material estimates.

Wall Height

Wall Length

Block Height

Block Length

Number of wall blocks

Number of cap blocks

Gravel for backfill

Thickness

Length

Height

Volume

Weight

Single wall block price

Single cap block price

Gravel price (per unit weight)

Total cost of wall blocks

Total cost of cap blocks

Total cost of gravel for backfill

Total expenses

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Enter your wall dimensions and block size to calculate the number of blocks needed.

How to Calculate Retaining Wall Blocks

Calculating the number of blocks needed for a retaining wall is straightforward once you know your wall dimensions and block size. The calculation follows a simple formula based on the total wall area.

Calculation Formula

The number of blocks needed is calculated using:

Wall Area (sq ft) = Length (ft) × Height (ft)

Number of Blocks = Wall Area ÷ Block Face Area (sq ft per block)

Step-by-Step Process

1. Measure your wall dimensions: Measure the total length and height of your retaining wall in feet and inches. Convert any inches to feet (divide by 12) for accurate calculations.
2. Calculate wall area: Multiply the length by the height to get the total wall area in square feet. For example, a wall that's 20 feet long and 4 feet tall has an area of 80 square feet.
3. Select your block size: Choose the block size you'll be using. Block sizes are typically measured in "face feet" - the exposed surface area of each block. Common sizes range from 0.17 to 0.67 face feet per block.
4. Calculate blocks needed: Divide the total wall area by the face area of one block. Round up to the nearest whole number to account for cutting and waste.
5. Add waste factor: It's recommended to add 5-10% extra blocks to account for cutting, breakage, and waste during installation.

Example Calculation

Let's say you have a wall that is 20 feet long and 4 feet tall:

Wall Area = 20 ft × 4 ft = 80 sq ft
Using Small blocks (0.17 face ft per block):
Blocks Needed = 80 ÷ 0.17 = 470.59 blocks
Add 10% waste: 470.59 × 1.10 = 517.65 blocks
Round up: 518 blocks needed

Understanding Retaining Wall Block Sizes

Retaining wall blocks come in various sizes, and understanding the "face feet" measurement is key to accurate calculations. The face feet measurement refers to the exposed surface area of each block, which is what you see when the wall is complete.

Block Size	Face Feet per Block	Typical Dimensions	Best For
Small	0.17 sq ft	16" × 8"	Decorative walls, garden borders
Medium	0.25 sq ft	18" × 8"	Residential retaining walls
Large	0.33 sq ft	24" × 8"	Commercial projects
Extra Large	0.50 sq ft	24" × 12"	Large retaining walls
Jumbo	0.67 sq ft	32" × 12"	Industrial applications

Note: Actual block dimensions may vary by manufacturer. Always check the specifications of the blocks you plan to use, as the face area can differ slightly between brands and styles.

Retaining Wall Installation Tips

Building a retaining wall requires careful planning and proper techniques to ensure it's both functional and long-lasting. Here are some essential tips to keep in mind:

Foundation Preparation

• Excavate a level trench for the base
• Compact the soil foundation properly
• Add 4-6 inches of compacted gravel base
• Ensure proper drainage behind the wall
• Check local building codes for requirements

Material Considerations

• Order 5-10% extra blocks for waste
• Use proper adhesive or mortar if needed
• Consider geogrid reinforcement for tall walls
• Plan for proper backfill materials
• Account for drainage pipe if required

Construction Best Practices

• Start with the first course perfectly level
• Use a level to check each row
• Step back the wall slightly (1 inch per foot of height)
• Stagger joints between blocks
• Compact backfill in layers

Safety and Maintenance

• Wear proper safety equipment
• Check for proper drainage annually
• Inspect for cracks or shifting
• Repair any damage promptly
• Consider professional help for tall walls

Frequently Asked Questions

How many blocks do I need for my retaining wall?

The number of blocks depends on your wall's length, height, and the size of blocks you're using. Use our calculator by entering your wall dimensions in feet and inches, then select your block size. The calculator will give you the exact number of blocks needed, plus we recommend adding 5-10% extra for waste and cutting.

What is "face feet" when talking about retaining wall blocks?

Face feet refers to the exposed surface area of each block, measured in square feet. This is the area you see when the wall is finished. For example, a block with 0.17 face feet has an exposed area of 0.17 square feet. This measurement is used to calculate how many blocks you need to cover your total wall area.

Do I need to add extra blocks for waste?

Yes, it's highly recommended to add 5-10% extra blocks to your total count. This accounts for blocks that need to be cut to fit corners or edges, breakage during handling, and any mistakes during installation. It's better to have a few extra blocks than to run short mid-project.

How do I measure my wall dimensions accurately?

Measure the total length of the wall along the ground where the wall will be built. For height, measure from the base of the wall (where it meets the ground) to the top of the finished wall. Use a tape measure and measure in feet and inches, then enter both values into the calculator for the most accurate results.

What other materials do I need besides blocks?

In addition to blocks, you'll need a compacted gravel base (typically 4-6 inches deep), backfill material (gravel or crushed stone), drainage pipe if needed, and possibly adhesive or mortar depending on your block type. Some walls also require geogrid reinforcement for additional strength, especially taller walls.

Can I use this calculator for curved walls?

This calculator is designed for straight walls. For curved walls, you'll need to measure along the curve length, which may require more blocks due to the angles and cuts needed. It's best to measure the curve length and use that as your "length" measurement, but add extra blocks (15-20%) to account for the additional cutting required.

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