Construction Calculator - Driveway and Sitework

Retaining Wall Calculator

Estimate retaining wall blocks from wall length and height.

Reviewed: August 26, 2026

Calculate Retaining Wall

For the Retaining Wall Calculator, enter wall length, wall height, unit face length, unit face height, waste allowance, and unit price. It divides wall face area by the installed unit-face module, applies allowance, and rounds up to whole masonry units with optional unit cost.

Construction measuring tools arranged beside a residential building project

Formula used

Units = ceil([wall area ÷ installed unit-face module] × [1 + waste ÷ 100])

Retaining Wall Calculator measurement plan showing Wall length feet, Wall height feet, Unit face length inches

Worked retaining wall example

Retaining Wall Calculator example: 29.1 ft × 4.88 ft = 142.01 ft². A 16-in × 8-in face module occupies 0.8889 ft², producing 173 units after 8% allowance and whole-unit rounding.

Reading the unit or bag result

Round wall units, caps, and corner units separately and match supplier pallet quantities; the displayed cost covers only the unit count entered.

Count every course, including buried work

Visible wall face area can omit the buried leveling course, stepped grade transitions, returns, corners, caps, and units used in curves or setbacks. Segmental wall systems also impose manufacturer limits for batter, reinforcement, drainage stone, and geogrid. This page counts face modules; it does not design wall stability or foundation conditions.

Details the area formula cannot see

Corners, curves, batter, buried base courses, cap units, stepped grades, setbacks, and cutting can add units beyond visible face area.

Questions specific to this calculation

Are buried base courses and cap units included automatically?

Measure the exposed wall face by sections and use the installed face module of the selected block, not a catalog name that may cover several sizes.