Retaining Wall Calculator

Blocks, caps, base gravel and drainage, with a height check.

Project Details
Enter your measurements and requirements
$
Results
Calculated estimates for your project
Courses7, one buried
Blocks294
Caps42
Base stone2.2 tons
Drainage stone4.4 cu yd
Drain pipe44 ft
Height, footing to top4 ft
Height checkUnder the height limit. Local rules can be stricter, so confirm with your building department
Checked againstIRC 2021 R105.2, not yet reviewed by a licensed professional
Estimated cost$2,484

Turn these numbers into a build plan.

  • 294 blocks
  • 42 caps
  • 4.0 ft height, footing to top
Materials List
Recommended materials and quantities
Blocks294
Caps42

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Project plan · built from your numbers

Block retaining wall, 40 ft long

40 ft of segmental block, 3.0 ft exposed, 7 courses with one buried.

Materials
$2,484
Time
2 weekends
Level
Advanced
6 steps 4 tools 7 materials
  1. 1

    Confirm the design

    Ask your building department whether this wall needs a permit, and call 811.

  2. 2

    Dig the trench

    Trench 40 ft, 2 ft wide, deep enough for 6" of base and one buried course.

  3. 3

    Compact the base

    Place and compact 2.2 tons of base, level along the wall.

01 · Your numbers
Blocks
294
Caps
42
Height, footing to top
4.0 ft
Est. cost
$2,484
02 · The plan

6 steps · 4 tools · 7 materials

3 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

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Block retaining wall, 40 ft long

Finished in 2 weekends · $2,484 DIY

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Borrow these 4 tools from neighborsFull how-to guide: Build a retaining wall

How to estimate a block retaining wall

Height is measured from the bottom of the footing to the top of the wall. See the retaining wall guide for construction details.

  1. Count courses. Divide the exposed height by block height and add one buried course.
  2. Count blocks. Divide the wall length by block length and multiply by courses.
  3. Size the base. Plan a trench about 2 ft wide with 6 in of compacted stone.
  4. Plan drainage. Run a perforated pipe at the base and backfill 12 in of washed stone.

Frequently asked questions

How tall can a retaining wall be without an engineer?

The 2021 IRC commonly exempts walls up to 4 ft from a permit, measured from the bottom of the footing, unless they hold a surcharge. Many cities are stricter, so ask your building department first.

What counts as a surcharge?

Any extra load above the wall, such as a driveway, a slope or a building. A surcharged wall should be designed by an engineer at any height.

Do I need drainage behind the wall?

Yes. Water pressure is a leading cause of failure. Use washed stone and a drain pipe that exits to daylight.

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