Enter your wall dimensions to get exact block counts, materials, costs, and a shopping list.

Diagram updates after you calculate.

Wall Dimensions

Wall Length (ft)

Please enter a valid length greater than 0.

Wall Height (ft)

Please enter a valid height greater than 0.

Block Dimensions

Block Preset (or enter custom below)

Block Face Length (in)

Enter a valid block length.

Block Height (in)

Enter a valid block height.

Setback per Course (in) (batter)

Buried Base Courses

Cost & Waste

Block Price Each ($)

Waste Factor (%)

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Total Blocks Needed (incl. waste)

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Courses (rows)

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Blocks per Course

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Base Course Blocks

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Estimated Block Cost

Course-by-Course Breakdown

Course	Type	Height from Base (in)	Blocks Needed

💡 Pro Tip

Always bury your first course at least 1" per foot of wall height — for a 3 ft wall, bury the base 3 inches minimum. Add a 6-inch compacted gravel base beneath the buried course for drainage. This prevents frost heave and keeps the wall plumb for years.

Time Estimate

🔨 Beginner

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First project

⚡ Experienced

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Done it before

Includes excavation, gravel base, laying blocks, and backfill. Assumes hand tools.

🛒 Materials Shopping List

Prices are US averages. Always call your local supplier for exact quotes.

Full Cost Estimate

Item	Qty	Unit Price	Total

Labor not included. Contractor labor typically adds $15–$25 per sq ft of wall face.

How to Use This Retaining Wall Block Calculator

Enter your wall's total length and height in feet, then choose a block preset or enter custom block dimensions in inches. Set your waste factor (10% is standard for straight walls, 15% for curves), and hit Calculate Blocks. You'll instantly get a total block count, a course-by-course breakdown, a full shopping list, and cost estimate.

Why This Matters

Ordering the wrong number of blocks is one of the most common and expensive DIY mistakes. Over-ordering wastes money — retaining wall blocks typically cost $2–$6 each and can't always be returned once delivered. Under-ordering halts your project mid-build and forces a second delivery charge, often $75–$150 extra.

A 20-foot wall at 3 feet high requires roughly 180–220 blocks depending on block size — that's a $400–$1,300 material investment. Getting it right upfront saves you real money and a trip to the hardware store mid-weekend. This calculator also accounts for the buried base course — a detail many homeowners forget, which can cause a wall to fail within a few years.

Whether you're building a garden bed border, terracing a sloped backyard, or creating a driveway edge, these numbers give you a reliable starting point before you talk to a supplier or pull out your wallet.

How It's Calculated

The core formula is straightforward:

Blocks per course = Wall Length (in) ÷ Block Face Length (in), rounded up
Number of courses = Wall Height (in) ÷ Block Height (in), rounded up
Base blocks = Blocks per course × (1 + buried courses factor)
Total blocks = Blocks per course × Total courses × (1 + waste%/100)

The buried base course adds one extra row underground for structural integrity. The setback (batter) is for reference — most segmental retaining wall blocks are designed with a built-in 1–2° setback angle, which helps the wall lean slightly into the hillside for stability.

Tips & Common Mistakes

Don't skip the gravel base. 4–6 inches of compacted ¾" crushed gravel under the base course is mandatory — skip it and frost heave will topple your wall in 2 winters.
Bury that first course. A 3-foot wall needs at least 3–4 inches buried. A 4-foot wall needs 4–6 inches. This is what locks the whole structure in place.
Stagger your joints. Like brickwork, each course should offset by half a block. This is structural, not decorative.
Add drainage behind the wall. Budget for a perforated drain pipe and filter fabric if your wall is retaining more than 2 feet of soil — water pressure behind a wall is the #1 cause of retaining wall failure.
Walls over 4 feet may need a permit. Check with your local municipality before breaking ground — many areas require engineering approval for walls over 4 feet tall.

Frequently Asked Questions

How many retaining wall blocks do I need per square foot?

It depends on block size. A standard 12"×4" block covers 0.33 sq ft of wall face, so you need about 3 blocks per square foot. A 12"×6" block covers 0.5 sq ft, needing about 2 blocks per sq ft. This calculator handles any size automatically — just enter your block dimensions.

What waste percentage should I use?

Use 10% for straight walls with no cuts. Bump it to 15% if your wall has curves, corners, or steps. If your design has lots of 45° corner cuts or curves, go up to 20%. It's always cheaper to have 3–5 extra blocks than to need an emergency reorder.

How deep should the base course be buried?

The general rule is 1 inch of burial per foot of wall height, with a minimum of 1 full course. So a 3-foot wall needs at least 3 inches buried (roughly one full course). This buried course plus a compacted gravel base is what keeps the entire wall from sliding or tipping forward over time.

Do I need cap blocks too?

Yes, for a finished look and to protect the top course from weathering, most people add cap blocks. Cap blocks are typically the same length as wall blocks but thinner (about 1.5–2 inches) and flat-faced. You'll need one cap block per face-length unit across the top — roughly the same count as one course of regular blocks.

Retaining Wall Block Calculator