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MaterialCalc — Retaining Wall Cost Calculator

Estimate prepared 09/01/2026. Estimates only; verify against your plans before ordering.

Retaining Wall Cost Calculator

Above finished grade. A course below grade is added automatically.

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Cuts at ends and curves. Curved walls run higher.

Result

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The block is usually less than half the cost of a retaining wall. Base stone, drainage stone, pipe, fabric, geogrid and the excavation behind the wall carry the rest, and on a tall wall the engineering and permit add more. This prices the whole job, and compares block against timber and natural stone.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Retaining wall block face area
96 in²

A common 12x8 in face. Check your block — face size varies a lot by product line.

Allan Block and Pavestone product data — Industry standard, varies by supplier, checked 09/01/2026

Compacted base under retaining wall
6 in

Segmental wall installation guides — Industry standard, varies by supplier, checked 09/01/2026

Drainage stone behind wall
12 in

Water behind a wall is what pushes it over. This is not the place to economize.

NCMA segmental retaining wall guidance — Industry standard, varies by supplier, checked 09/01/2026

Wall height buried below grade
0.1

Roughly one course in ten, minimum one full course, sits below finished grade.

NCMA segmental retaining wall guidance — Rough figure — widens the estimate range, checked 09/01/2026

Crushed gravel density
105 lb/ft³

Compacted 3/4 in crushed stone. Varies by quarry and moisture; loose stone runs lighter.

USGS aggregate bulk density range — Industry standard, varies by supplier, checked 09/01/2026

Compaction allowance
0.2

Loose stone loses roughly a fifth of its volume once compacted, so order above the finished volume.

Standard earthwork practice — Rough figure — widens the estimate range, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Wall face area = length × (exposed height + buried course). Blocks = face area ÷ block face area. Base and drainage stone are volumes converted to tons at 105 lb per cubic foot. Geogrid layers go in every third course above the first, extending back roughly four block depths.

Worked examples

40 ft wall at 48 in exposed

Wall length: 40 Exposed wall height: 48 Waste: 10

Right on the engineering threshold. Roughly 320 blocks, 6 tons of stone and geogrid layers — the stone and grid together rival the block cost.

30 ft wall at 24 in

Wall length: 30 Exposed wall height: 24 Waste: 10

Below every threshold: no engineering, usually no permit, no geogrid. This is the height where a retaining wall is genuinely a DIY project.

80 ft wall at 36 in

Wall length: 80 Exposed wall height: 36 Waste: 10

Long rather than tall, so no engineering, but roughly 480 blocks and 8 tons of stone. Length costs materials; height costs paperwork.

Choosing materials

  • Stone is the line item that surprises people. A 40 ft wall at 4 ft high wants around 6 tons of drainage stone plus base — well over $400 delivered, before anyone touches a block.
  • Above 4 ft you are usually into engineering, permits and inspections. The design fee alone can be $800 to $2,000, and it is not optional where the code requires it.
  • Excavation behind the wall is real work. You are digging a trench a foot wide the full height of the wall, plus the geogrid embedment, and on a slope that is a machine job.
  • Timber walls are cheaper to buy and much more expensive to own. Pressure-treated timber in ground contact behind a wall of wet soil has a 15 to 20 year life; block does not rot.
  • Terracing two short walls instead of one tall one often costs less than the engineering for the tall one, and it always looks better. Consider it before committing to height.

Common questions

How much does a retaining wall cost per square foot?

Materials typically run $12 to $22 per square foot of wall face for segmental block including base and drainage. Installed by a contractor, $30 to $60 per square foot, rising sharply above 4 ft where engineering and geogrid come in.

What is the cheapest retaining wall material?

Pressure-treated timber is cheapest to buy and the most expensive to own — 15 to 20 years in wet ground contact. Segmental block costs more up front and lasts indefinitely. Over any reasonable ownership period, block is cheaper.

Why is drainage stone such a large part of the cost?

Because you need a foot-wide zone of it the full height of the wall, plus a compacted base beneath. On a 40 ft wall 4 ft high that is around 6 tons. It is also the part that determines whether the wall stands, so it is not a place to economize.

When does a retaining wall need engineering?

Most jurisdictions set the line at 4 ft measured from the bottom of the footing, and lower if the wall retains a surcharge — a driveway, a structure, or a slope above it. Expect $800 to $2,000 for the design plus permit fees.

Can I build a retaining wall myself?

Up to about 3 ft on level ground with no surcharge, yes — it is heavy work but not technical. Above that, the consequences of getting the drainage or the geogrid wrong are a wall that fails and takes the slope with it.

Is terracing cheaper than one tall wall?

Often, yes. Two 3 ft walls set well apart avoid the engineering, permit and geogrid that one 6 ft wall triggers. They must be spaced far enough apart that the upper wall does not surcharge the lower one — usually twice the wall height.

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