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Masonry

Retaining Wall Calculator USA 2026

Estimate segmental retaining-wall blocks, base gravel and drainage backfill for a landscape or grade-change wall.

Reviewed by BuildMate Editorial Team Construction Researchers Updated March 2026 2 min read Fact-checked

Used by

250,000+ homeowners

Avg. time

~15 seconds

Updated

2026

Accuracy

Pro estimation

Works on: Desktop Tablet Mobile No registration required
Unit system

Enter your measurements

Results

Blocks per course

20

Total courses

10

Wall blocks

200

Cap blocks

20

Base gravel

0.41 yd³

Calculation steps
  1. 1.Blocks per course = ⌈(20×12) ÷ 12⌉ = 20
  2. 2.Courses = ⌈(3×12) ÷ 4⌉ + 1 buried = 10
  3. 3.Total wall blocks = 20 × 10 = 200

Includes a standard waste allowance. Verify with your supplier before ordering.

Stored on this device — no account needed.

What this calculator does

Calculates how many blocks, bricks or bags of mortar you need for a wall or column, including a standard 5–10% waste factor for cuts and breakage.

When to use it

  • Building a garden wall, retaining wall or column.
  • Estimating material for a fireplace or chimney.
  • Bidding a brick veneer install.

Common mistakes

  • Forgetting mortar joints in the block count.
  • Not accounting for cap block and half-blocks at ends.
  • Skipping rebar and grout for structural walls.

Pro tips

  • Buy one extra pallet vs. running out mid-course.
  • Use Type S mortar for load-bearing, Type N above grade.
  • Dry-lay the first course to plan cuts.
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Disclaimer: Estimates based on 2026 RSMeans USA data. Actual quantities vary by site conditions, waste and installer practices. Verify with your supplier or contractor before ordering.

How it works

  1. 1Enter wall length and finished height.
  2. 2Pick a block size (standard 12" wide × 4" tall).
  3. 3We add 1 buried course and estimate base and cap.

Formula

Blocks per course = Length ÷ Block Length → Courses = Height ÷ Block Height

Worked example

A 20 ft × 3 ft wall with 12×4 block = 20 blocks/course × 9 courses = 180 blocks + caps.

Frequently asked questions

How deep should the base be?

6" of compacted gravel, and bury the first course 1" per foot of finished height.

Do I need geogrid?

For walls above 3–4 ft, yes — every 2 courses.

Is the Retaining Wall Calculator free to use?

Yes — every BuildMate calculator is 100% free, requires no signup and works offline once the page has loaded.

How accurate are these estimates?

Formulas follow 2026 industry standards (RSMeans, ICC and manufacturer specs). Real-world results vary by site conditions, waste and installer practices — always get 2–3 written quotes from licensed pros before committing.

Can I save my calculation?

Yes. Hit the Save button after you run an estimate — it's stored on this device (no account needed) and you can access it anytime from the Saved drawer.

Can I compare two projects side-by-side?

Yes. Add estimates to Compare and open the Compare drawer to see them side-by-side, then use Download PDF or Email to share the comparison.

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