Retaining Wall Calculator

Q: How much does a retaining wall cost?

A block retaining wall costs $20 to $60 per square foot of wall face professionally installed, with most homeowners paying $25 to $40 per square foot. A typical 30 ft by 3 ft wall (90 sq ft) runs $2,700 to $5,400 installed, or $1,000 to $1,800 in materials if you build it yourself.

Retaining walls cost $20 to $60 per sq ft of wall face installed, with most block walls landing at $25 to $40 per sq ft. A typical 30 ft by 3 ft wall runs about $2,700 to $5,400 installed. Enter your wall size below to get block count, gravel quantities, and total cost.

Estimated total—

Your wall

Wall length Wall height

Unit

feetmeters

Block face (in) Block height (in)

Price assumptions

Block ($ each) Cap block ($ each) Gravel ($/cubic yd, delivered) Installation labor ($/sq ft)

Defaults & assumptions

Defaults: a typical 30 ft by 3 ft wall, standard 12 in by 4 in segmental (interlocking) blocks, and US national average rates. Adjust the rates above to match local quotes. Set labor to 0 for a DIY materials estimate. Gravel includes a 6 in compacted base and 12 in of drainage backfill.

Enter your wall length and height above to see results.

Retaining wall cost per square foot

Segmental block (the interlocking, mortarless kind) is the most common residential retaining wall and runs $20 to $40 per sq ft installed. Poured concrete and natural stone cost more, at $30 to $60 per sq ft and $40 to $75 per sq ft respectively. Materials are roughly a third of the price: blocks cost $2 to $8 each, and gravel runs $35 to $55 per cubic yard delivered. Labor covers excavation, base compaction, laying courses, and backfilling. Height drives cost fastest, since taller walls need wider bases, more backfill, and above 3 to 4 ft, engineering and permits.

Typical block retaining wall cost by size (US averages, installed)
Wall size	Face area	DIY materials	Installed
20 ft by 2 ft	40 sq ft	$450 to $800	$1,200 to $2,400
30 ft by 3 ft	90 sq ft	$1,000 to $1,800	$2,700 to $5,400
50 ft by 3 ft	150 sq ft	$1,700 to $3,000	$4,500 to $9,000
50 ft by 4 ft	200 sq ft	$2,300 to $4,000	$6,000 to $12,000

How the calculator works

Blocks = wall face area (length × height) ÷ one block’s face area, rounded up. Cap blocks run the top course, one per cap length. Gravel is a 6 in deep by 24 in wide compacted base trench plus a 12 in wide drainage column behind the full wall face, converted to cubic yards and tons. Labor is priced per square foot of face, the way contractors quote it. Price ranges reflect published US averages from national cost guides (Angi, HomeGuide, HomeAdvisor, 2026). Not included: engineering and permits for walls over 3 to 4 ft, a perforated drain pipe at the base (see our french drain calculator), and re-turfing the slope afterward (see the sod calculator).

Retaining wall cost FAQ

How much does a retaining wall cost?

A block retaining wall costs $20 to $60 per sq ft of wall face professionally installed, with most homeowners paying $25 to $40 per sq ft. A typical 30 ft by 3 ft wall (90 sq ft) runs $2,700 to $5,400 installed, or $1,000 to $1,800 in materials if you build it yourself.

How many blocks do I need for a retaining wall?

Divide the wall face area (length times height) by one block’s face area. A standard 12 in by 4 in segmental block covers about a third of a square foot, so a 30 ft by 3 ft wall (90 sq ft) needs about 270 blocks plus one cap block per foot of wall. Buy 5 to 10 percent extra for cuts at corners and curves.

Do I need gravel behind a retaining wall?

Yes. Drainage is what keeps a retaining wall standing. Standard practice is a compacted gravel base 6 in deep (buried below the first course) and a 12 in wide column of drainage gravel directly behind the wall, often with a perforated drain pipe at the base. Skipping backfill gravel is the most common cause of leaning and failure.

How tall can I build a retaining wall without an engineer?

Most US jurisdictions allow walls up to 3 to 4 ft high without a permit or engineering. Above that height, or any height if the wall supports a driveway, slope, or structure, you typically need an engineered design and permit. Budget $500 to $3,000 extra and check your local building department first.