Free project planning tool

Retaining Wall Calculator — Blocks and Base Gravel

Estimate face units and base aggregate for a straight segmental landscape wall; enter exposed wall size and the selected product dimensions.

Formula reviewedJuly 23, 2026Inputs stay on your device

Enter your measurements

US customary units

Wall length

Fractions work. You can enter 12' 6 1/2" instead of converting it first.Exposed wall height

Fractions work. You can enter 12' 6 1/2" instead of converting it first.Block face length

Fractions work. You can enter 6 1/2 instead of converting it first.Block face height

Fractions work. You can enter 6 1/2 instead of converting it first.Compacted base width

Fractions work. You can enter 6 1/2 instead of converting it first.Compacted base depth

Fractions work. You can enter 6 1/2 instead of converting it first.Block waste

Inputs stay on this device. Saved work syncs privately only when you choose to sign in; shared links include only the measurements in that link.

Calculated estimate

152

wall blocks

Estimated retaining-wall blocks

Full courses6

Cap units with waste26

Loose base gravel estimate1.22 yd³

Live planning viewSchematic · not to scale

Wall length30 ftExposed wall height3 ftBlock face length16 in

Estimated retaining-wall blocks152 wall blocks

Material takeoff only. A qualified design may be required for embedment, drainage, surcharge, reinforcement, setbacks, permits, utilities, and taller or critical walls.

CalcurHome project estimate

Retaining Wall Calculator — Blocks and Base Gravel

Entered measurements

Wall length: 30 ft
Exposed wall height: 3 ft
Block face length: 16 in
Block face height: 6 in
Compacted base width: 24 in
Compacted base depth: 6 in
Block waste: 10 %

Estimate

152 wall blocks

Estimated retaining-wall blocks

Full courses6

Cap units with waste26

Loose base gravel estimate1.22 yd³

Plan on 152 blocks plus 26 cap units for 6 full courses.

Material takeoff only. A qualified design may be required for embedment, drainage, surcharge, reinforcement, setbacks, permits, utilities, and taller or critical walls.

Planning estimate only. Verify quantities, local prices, codes and structural decisions before purchase or construction.

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What does the retaining wall calculator calculate?

Divide exposed wall height by block face height for courses, then divide length by block face length for units per course. Round both up and add waste. This tool also estimates compacted base gravel, but it does not design embedment, drainage, reinforcement, bearing, or wall stability.

Retaining-wall block takeoff formula

Courses = round up(wall height ÷ block height); blocks/course = round up(wall length ÷ block length); blocks = round up(courses × blocks/course × waste factor).

Rounding courses and rows separately avoids fractional units. Base gravel uses trench length, width, and compacted depth, then adds a fixed 10% loose-volume planning allowance.

How to measure for an accurate estimate

Measure along the wall face or centerline consistently, including returns as separate segments.
Use exposed height for the displayed courses, then follow the design for buried units and embedment.
Enter nominal face dimensions from the specific block data sheet, not pallet dimensions.
Measure base trench width and compacted thickness from the approved installation detail.

Three-foot garden retaining wall

A 30 ft by 3 ft exposed wall uses 16-by-6-in faces, 24-by-6-in base, and 10% block waste.

Six courses need 138 net blocks; order 152 blocks, 25 caps, and about 1.22 yd³ of loose base gravel.

Before you purchase material

Use one compatible block, cap, corner, adhesive, reinforcement, and drainage system.
Check whether corners and curves require special units or increased cutting waste.
Order base aggregate and wall drainage stone separately because their gradations may differ.
Verify engineering and permit thresholds locally before purchasing or excavating.

Common questions

Does the calculator include buried retaining-wall blocks?

No. The entered height represents exposed face, and the block total covers those rounded courses. Required embedment depends on the system, slope, soil, frost, and design. Add buried courses from the approved detail or increase the entered wall height accordingly.

How much block waste should I add?

Ten percent is a planning allowance for cuts, breakage, selection, and layout. Long straight walls using full modules may need less; tight curves, corners, stairs, and color blending may need more. Confirm return policy and lot availability before ordering excess.

How tall can I build a retaining wall without engineering?

There is no universal height. Permit and engineering thresholds vary by jurisdiction and may consider total retained height, slopes, surcharge, property lines, utilities, and consequences of failure. Contact the local building authority and block-system guidance before setting the design.

Does base gravel also cover drainage stone behind the wall?

No. The calculated gravel is only the entered base trench plus a 10% loose-volume allowance. Drainage aggregate behind and within units depends on block depth, wall height, drain location, and system detail. Calculate that specified zone separately.

Sources and reference standards

Federal Highway Administration — Segmental Retaining Wall BlocksFederal research on segmental retaining-wall block performance, durability, moisture, and freeze-thaw exposure.
Federal Highway Administration — Gravel Roads Construction and Maintenance GuideFederal guidance on aggregate selection, placement, moisture, and compaction.

See every citation and the calculators that use it in the calculator source index.

Project workflows

Use this result in a complete project plan

Retaining wall planning guide

A retaining wall holds back soil and can redirect water, so exposed face area is only the visible part of the project. Total retained height, slopes, surcharge, soil, groundwater, foundations, reinforcement, setbacks and failure consequences determine the design. This guide starts with those conditions and uses calculators only for quantities supported by a verified wall concept.

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