Type in your wall length and finished height and get the full shopping list — wall blocks with waste, cap blocks, the gravel base trench and the drainage gravel behind the wall, with the total cost. No sign-up. The working is shown under every number.
Quick example: a 20 ft long, 2 ft high wall in 6 × 16 in blocks needs 83 blocks, 17 cap blocks, 1.0 cubic yard of base gravel and 2.0 cubic yards of drainage gravel — $749.00 at the example prices.
| Item | Buy | Cost |
|---|---|---|
| Estimated total | $0.00 |
Drainage gravel goes behind the wall with a perforated drain pipe at the base — the pipe is not priced here (allow one length per wall). A layer of landscape fabric behind the blocks keeps soil out of the gravel.
Estimate only — not a guarantee. Mistakes are possible, so always check the quantities with your supplier or a builder before you buy or build.
With 6 × 16 in blocks, each row of a 20 ft wall takes 15 blocks (240 in ÷ 16 in), and a 2 ft exposed wall takes 4 rows plus 1 buried starter course — 5 rows in total, so 75 blocks, and 83 to buy once the 10% waste allowance is added.
The first course of a block wall is normally buried below ground level to stop the wall sliding and to keep the base out of the frost. This calculator counts one buried course (you can untick it), based on the finished height you want above ground.
The base is a trench 6 in deep and 12 in wider than the block, filled with compacted gravel. A 20 ft wall with 12 in deep blocks needs 0.74 cubic yards, rounded up to a 1.0 cubic yard order.
This calculator allows a 12 in wide column of clean drainage gravel behind the blocks for the full built height of the wall. A 20 ft wall built 2.5 ft high (2 ft showing plus the buried course) needs 1.85 cubic yards, rounded up to 2.0 cubic yards.
Most block manufacturers rate their standard blocks for walls up to about 4 ft of exposed height; anything taller, or a wall holding back a slope, driveway or building, usually needs an engineered design, geogrid reinforcement and often a permit. This calculator plans materials only — check your local rules before building over 4 ft.
| Wall (length × height) | Blocks | Cap blocks | Base gravel | Drainage gravel | Total |
|---|---|---|---|---|---|
| 10 ft × 2 ft | 44 | 9 | 0.5 cu yd | 1.0 cu yd | $392.50 |
| 20 ft × 2 ft | 83 | 17 | 1.0 cu yd | 2.0 cu yd | $749.00 |
| 20 ft × 3 ft | 116 | 17 | 1.0 cu yd | 3.0 cu yd | $1,013.50 |
| 40 ft × 3 ft | 231 | 33 | 1.5 cu yd | 5.5 cu yd | $1,967.00 |
Block counts include the buried starter course and 10% waste. Base gravel is a 6 in deep trench 12 in wider than the block; drainage gravel is a 12 in wide column behind the wall for its full built height; both are rounded up to the nearest 0.5 cubic yard. Totals use the example prices in the calculator above.
These figures are planning estimates only — not a guarantee and not professional advice. Mistakes are possible, including through an error in this calculator. Always check the quantities, sizes, spacings and depths with your supplier, a licensed builder, and your local building code before you buy materials or start work. The owner of this site accepts no responsibility or liability for any loss, cost, damage, injury, wasted material or failed inspection that results from using these estimates. Prices are examples to start from, not live prices or quotes.