Retaining Wall Block Calculator: Blocks per Course

This calculator counts the blocks for a low garden wall or raised border built from stacking blocks. Enter the wall length and height in feet, the face length and height of one block in inches, and a waste allowance; you get blocks per course, the number of courses and the total blocks to buy.

Formula

Blocks per course = wall length (in) ÷ block face length, rounded up. Courses = wall height (in) ÷ block face height, rounded up. Blocks to buy = blocks per course × courses × (1 + waste ÷ 100), rounded up.

• len1: wall length in feet, measured along the face
• h: total height in feet, including a buried first course if the maker calls for one
• bl, bh: face length and height of one block in inches
• waste: allowance for cut and broken blocks

Worked Example

A wall 30 ft long and 2 ft high, 12 in × 4 in blocks, 5% extra.

1. Per course = 30 × 12 ÷ 12 = 30 blocks
2. Courses = 2 × 12 ÷ 4 = 6 courses
3. Blocks = 30 × 6 × 1.05 = 189 blocks

How to use the result

Order the total, plus cap units if the wall has a cap course (count those from the length and the cap length). Ask for blocks from one production run so the colour matches.

Limits and common mistakes

• This counts blocks only. It does not size a wall to hold back soil: walls above the height the block maker allows, walls on slopes or near driveways, and walls holding back loads need a qualified designer, and many places need a permit.
• Curved walls and corners change the count slightly; add waste for them.
• Base gravel and drainage stone are extra materials.

Frequently Asked Questions

How many blocks do I need for a 10 ft wall 2 ft high?

With 12 × 4 in blocks: 10 per course × 6 courses = 60 blocks, plus waste.

Should the first course be buried?

Many block makers call for it; follow the instructions for your block.

Does block depth matter for the count?

No, only the face length and height set the count; depth matters for the wall’s strength.

How tall can I build a block wall myself?

That depends on the block system, soil and local rules; check the maker’s limits and local regulations.

in len1 | Wall length | ft | 30 | 0 | 10000
in h | Wall height (including any buried course) | ft | 2 | 0 | 10
in bl | Block face length | in | 12 | 1 | 72
in bh | Block face height | in | 4 | 1 | 36
in waste | Extra for cuts and breakage | % | 5 | 0 | 50
out tot | Blocks to buy | blocks | ceil(round(ceil(round(len1 * 12 / bl, 6)) * ceil(round(h * 12 / bh, 6)) * (1 + waste / 100), 6)) | 0
out per | Blocks per course | blocks | ceil(round(len1 * 12 / bl, 6)) | 0
out rows | Courses | courses | ceil(round(h * 12 / bh, 6)) | 0