Retaining Wall Block Calculator
Count blocks, caps, base gravel and backfill for a retaining wall.
Enter your values
Enter the wall length in ft.
Enter the wall height in ft.
Enter the block width in in.
Enter the block height in in.
Enter the cost per block in $.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Blocks needed
- 180 (+10% waste: 198)
- Cap blocks
- 20
- Courses
- 9 at 20 per course
- Base gravel
- 0.37 cubic yards
- Block cost
- $693.00
Working
- 120 blocks/course x 9 courses = 180 blocks
Quick answer
Blocks = wall face area divided by the face area of one block, plus caps along the top and a compacted gravel base under the first course.
blocks = (length x height) / (block width x block height)
At a glance
| What it does | Count blocks, caps, base gravel and backfill for a retaining wall. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Wall length, Wall height, Block width, Block height, Cost per block |
| Main output | Blocks needed |
| Formula | blocks = (length x height) / (block width x block height) |
| Cost | Free — no sign-up, no download |
How to use the Retaining Wall Block Calculator
- 1Measure the finished wall length and height above grade.
- 2Enter your block's face width and height from the product page.
- 3Order about 10% extra for cuts at corners and curves.
Inputs explained
- Wall length(ft)
- Enter the wall length in ft.
- Wall height(ft)
- Enter the wall height in ft.
- Block width(in)
- Enter the block width in in.
- Block height(in)
- Enter the block height in in.
- Cost per block($)
- Enter the cost per block in $.
Worked example
Using the values the calculator loads with:
Inputs
- Wall length20 ft
- Wall height3 ft
- Block width12 in
- Block height4 in
- Cost per block3.50 $
Results
- Blocks needed180 (+10% waste: 198)
- Cap blocks20
- Courses9 at 20 per course
- Base gravel0.37 cubic yards
- Block cost$693.00
- 20 blocks/course x 9 courses = 180 blocks
Frequently asked questions
How deep should the base course sit?
Bury roughly one block course, or 10% of wall height, on 6 inches of compacted gravel so the wall cannot slide forward.
When do I need engineering?
Most manufacturers require a design for walls over 4 feet, or any wall holding a slope, driveway or structure above it.
What do I need to enter into the Retaining Wall Block Calculator?
Just 5 values: wall length, wall height, block width, block height, cost per block. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Retaining Wall Block Calculator work out the answer?
Blocks = wall face area divided by the face area of one block, plus caps along the top and a compacted gravel base under the first course. It applies the formula blocks = (length x height) / (block width x block height) and shows the working so you can check each step by hand.
Is the Retaining Wall Block Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.