20×2 ft wall, 16×8 in blocks
Input
20 ft × 2 ft · 16×8 inOutput
45 blocks · 15/row × 3 coursesceil(20/1.33)=15 rows; ceil(2/0.67)=3 courses.
Retaining wall block count is **rows × courses**.
**Formula:**
Blocks per row = ceil(Wall length ft ÷ Block length ft)
Courses = ceil(Wall height ft ÷ Block height ft)
Base blocks = Blocks per row × Courses
Order blocks = ceil(Base × (1 + buffer% / 100))
**Example — 20 ft × 2 ft wall, 16×8 in blocks:**
Block length = 16 ÷ 12 = 1.33 ft
Blocks per row = ceil(20 ÷ 1.33) = **15**
Courses = ceil(2 ÷ 0.67) = **3**
Base blocks = 15 × 3 = **45**
Add **10–15% buffer** for corners, curves, and cut blocks. Cap blocks, geogrid, and drainage gravel are **separate**.
The calculator assumes a straight wall on level footing. Each course stacks full blocks; partial blocks at ends are counted via ceiling on row and course counts.
Formula
blocks = ceil(ceil(L/blockL) × ceil(H/blockH) × (1 + buffer%/100))Tap 20 ft × 2 ft garden terrace, 40 ft × 3 ft slope wall, or 12 ft × 18 in edging wall.
Measure along the wall face at the base. Height is from footing to top of wall — not including buried base course if set below grade.
Read length × height from the supplier tag. Standard segmental blocks are often 16×8 in or 18×12 in.
Results show blocks per row, number of courses, and total blocks to order.
Enable 10–15% buffer for curves, corners, and cut blocks. Order cap blocks separately.
Input
20 ft × 2 ft · 16×8 inOutput
45 blocks · 15/row × 3 coursesceil(20/1.33)=15 rows; ceil(2/0.67)=3 courses.
Input
40 ft × 3 ft · 16×8 inOutput
180 blocks base30 per row × 6 courses before buffer.
Input
12 ft × 1.5 ft · 12×4 inOutput
54 blocks base12 per row × 4.5 → 5 courses.
Input
45 base blocks + 10%Output
50 blocks to orderceil(45 × 1.1) = 50.
Common real-world scenarios where this tool saves time.
20 ft × 2 ft with 16×8 in blocks: 15 per row × 3 courses = 45 blocks. Compact gravel base and level first course.
40 ft × 3 ft terrace: more courses — add 15% buffer for stepped footing and cuts.
12 ft × 18 in with 12×4 in cap-style blocks: single course may suffice — verify height on block tag.
6 m × 0.6 m wall with 40×20 cm blocks — calculator converts to imperial layout math.
Step-by-step chains that connect related tools for common tasks.
Blocks, base, fabric, and drainage.
| Block | Length | Height | Typical use |
|---|---|---|---|
| Standard | 16 in | 8 in | Garden terrace walls |
| Large | 18 in | 12 in | Taller landscape walls |
| Cap/edging | 12 in | 4 in | Wall caps and low edging |
Always verify actual dimensions on your supplier tag.
Read **actual dimensions** on the supplier tag — nominal 16 in blocks may be 15⅝ in.
First course is often **partially buried** for stability — add height or order extra blocks.
Install perforated drain tile and gravel backfill — use Gravel Depth and Landscape Fabric calculators.
Walls over **3–4 ft** often require engineered plans, geogrid, and permits — check local code.
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With standard 16×8 in blocks: 15 per row × 3 courses = 45 blocks before buffer. Add 10% → 50 blocks.
Divide wall length by block length in feet and round up. 20 ft ÷ 1.33 ft = 15 blocks per row.
Divide wall height by block height in feet and round up. 2 ft ÷ 0.67 ft = 3 courses for 8 in tall blocks.
10% for straight walls, 15% for curves and many corners. Cap blocks are ordered separately.
Manufacturer specs often require geogrid above ~3–4 ft or for load-bearing walls. This calculator does not include geogrid.
Landscape fabric, 12–18 in drain rock, and perforated drain tile. Calculate fabric and gravel separately.
Wall dimensions are processed only in your browser — EverydayTools does not collect or store your measurements.
Block counts only — not structural engineering. Walls above local height limits need professional design and permits.
Part of Calculator Tools
More free tools for the same workflow.
Free gravel depth calculator: path or pad footprint and layer depth → cubic yards, bags, and coverage tables. Walkway, driveway, and paver base presets with compaction buffer. Imperial or metric. Runs locally in your browser.
Free sand calculator: patio footprint and bedding depth → cubic yards, bags, and bulk vs bag guidance. Paver bedding presets, round patio mode, order buffer. Imperial or metric. Runs locally in your browser.
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Reviewed on 2026-06-28.
Block size