Retaining Wall Gravel Calculator
Base and drainage stone for the wall, in m³, yd³ and tons.
Indicative estimate · not a survey or a design · see methodology
Where does the wall go? Draw the plot, read the slope and place the wall along the contour.
Open the plannerSegmental wall rules of thumb
| Item | Rule | Why |
|---|---|---|
| Buried course | 1 in per 8 in of height, min 6 in | Locks the base against sliding |
| Base | 6 in compacted gravel, 24 in wide | Prevents settlement |
| Drainage zone | 12 in of clean stone behind the wall | Relieves water pressure |
| Drain pipe | 4 in perforated at the base, daylighted | Carries water away |
| Setback (batter) | ¾–1 in per course | Leans into the slope |
| Engineering | Above 4 ft (3 ft in some cities) | Surcharge and soil loads |
Source: NCMA "Segmental Retaining Wall Installation Guide"; manufacturer installation guides (Allan Block, Versa-Lok): bury 1 in per 8 in of height (min 6 in), 6 in compacted base, 12 in drainage zone, walls over 4 ft require engineering in most US jurisdictions · verified 2026-08-22
How the take-off is calculated
total height = exposed + buried (max(6 in, 10 % of height)) · courses = ⌈total ÷ block height⌉ · blocks = courses × ⌈length ÷ block width⌉ × (1 + waste) · base gravel = length × 24 in × 6 in · drainage stone = length × 12 in × total height
A 10 m wall, 1 m exposed, 12 × 4 in blocks: buried 0.15 m → 1.15 m total → 12 courses × 33 blocks = 396, +5 % = 416 blocks; base gravel 0.9 m³, drainage stone 3.45 m³, about 7.3 t of gravel.
- Standard 12 in wide × 4 in high block face; change the size for your product.
- Single straight run; add 10 % for curves and corners.
- Walls with a slope or driveway above them (surcharge) need engineering even when low.
What people use it for
Terracing a sloped lot
Two 3 ft walls are cheaper and safer than one 6 ft wall and usually avoid engineering.
Driveway cut
A road above the wall is a surcharge: engineered design regardless of height.
Garden bed
Under 2 ft: base and drainage still matter; skip nothing.
Frequently asked questions
How many retaining wall blocks do I need?
Courses (total height ÷ block height) × blocks per course (length ÷ block width), plus about 5 % waste. The calculator includes the buried first course.
How deep should a retaining wall base be?
Bury one inch of wall per 8 inches of height (minimum 6 in) on 6 in of compacted gravel.
Do I need a permit for a retaining wall?
Most US jurisdictions require an engineered design and permit above 4 ft (some above 3 ft) or when there is a surcharge above the wall.
How much gravel goes behind a retaining wall?
A 12 in wide drainage zone for the full height: about 0.3 m³ per metre of a 1 m wall, or 1 ton per 10 ft.
How much does a retaining wall cost?
Typically $20–60 per square foot of face for segmental block installed; multiply the face area (length × height) by your local rate.
Do retaining walls need drainage?
Always: water pressure is what pushes walls over. Clean stone behind the wall and a perforated pipe at the base.
Related tools
Sources and author
Terramify editorial team · Research and data verification · Updated August 22, 2026
Source: NCMA "Segmental Retaining Wall Installation Guide"; manufacturer installation guides (Allan Block, Versa-Lok): bury 1 in per 8 in of height (min 6 in), 6 in compacted base, 12 in drainage zone, walls over 4 ft require engineering in most US jurisdictions
Indicative estimate · not a survey or a design · see methodology