Retaining wall calculator and estimator

How to calculate retaining wall blocks and courses

Measure the length along the actual wall alignment. For a straight wall, that is the end-to-end length. For a curve, use the arc length along the line where you measured your block width. Do not substitute the straight chord across the curve. Divide a wall with changing heights into sections and estimate each section separately.

Enter the exposed height of the block face, excluding the cap, and the number of buried courses shown on your plans. The calculator rounds the exposed height up to a full course, then adds the buried courses. A desired height of 37 inches with 6-inch-high units therefore needs seven exposed courses, not 6.17 courses. That means 42 inches of constructed exposed blockwork before the cap.

For each section, it also rounds the number of units across one course up to a whole unit. It multiplies the two rounded counts before adding a cutting and breakage allowance. This is a purchasing estimate: a cut piece may be reused, corner units may be different, and a manufacturer’s pattern can change the final schedule.

Units per course = ceil(length ÷ unit length)
Courses = ceil(exposed height ÷ unit height) + buried courses
Order units = ceil(units per course × courses × (1 + waste ÷ 100))

Retaining wall base gravel and drainage stone quantities

The leveling pad beneath the wall and the drainage zone behind it are separate quantities. Base volume is length × trench width × compacted base depth; drainage volume is length × drainage width × drainage height. Divide cubic feet by 27 for cubic yards. Stone allowance is applied separately. The starting dimensions are examples, not universal construction details. Confirm the specified zones and aggregate with your plans and supplier.

Buried retaining wall blocks, caps and hollow-core fill

Buried courses are included in the wall-unit total; the starting one-course setting is editable and is not an embedment specification. Caps can have a different installed length from face units. For a 30 ft run with 16 in coverage, 23 net caps become 26 after a 10% allowance. Enter any supplier-specified hollow-core fill per unit; the starting value is zero. Concrete grout is separate.

Convert retaining wall gravel volume to tons or tonnes

Volume and mass are different: multiply stone volume by the supplier’s bulk density to convert it to weight. The illustrative starting density is 1.4 US short tons per cubic yard; actual density varies with material, moisture and whether it is loose or compacted. A US short ton is 2,000 lb and a metric tonne is 1,000 kg. Use a separate stone allowance for handling and compaction.

Retaining wall drain pipe, fabric and cap adhesive

Pipe length is wall run plus the entered outlet allowance; fittings need a separate schedule. Fabric covers one rear face and one bottom strip plus the entered overlap, rather than a full enclosure. Adhesive depends on bead count and coverage per tube: a 30 ft run with two beads, 30 ft per tube and 10% allowance needs three tubes. Confirm drainage details and product instructions.

A complete worked example: 30 feet × 3 feet

Start with a 30-foot straight wall and 3 feet of exposed block height. Choose 16-inch-long by 6-inch-high units, one buried course, and 10% block waste. There are ceil(360 ÷ 16) = 23 units per course, six exposed courses, and seven courses including the buried row.

The net count is 23 × 7 = 161 units. Of these, 138 are exposed and 23 are buried. Applying 10% allowance gives ceil(161 × 1.10) = 178 units to order. With an entered 75 units per pallet, that means three whole pallets if the supplier only sells full pallets. The calculator’s unit-price cost is still based on 178 units, so ask whether pallet-only purchasing changes your invoice.

With a 22-inch-wide base trench and 6 inches of compacted base depth, net base volume is 30 × (22 ÷ 12) × 0.5 ÷ 27 = 1.02 yd³. A 12-inch drainage zone behind the constructed 3.5-foot block height, less a 6-inch soil cap, adds 3.33 yd³. A 10% stone allowance produces about 4.79 yd³ in total, excluding hollow-core fill. At the illustrative density, that is about 6.70 US tons.

At 16 inches per cap, the net count is 23 caps and the order quantity is 26 after waste. Pipe is 34 feet with the default 4-foot outlet allowance. Change any input to match your product or plans and print the revised takeoff for your supplier.

Estimate retaining wall cost from local quotes

Replace the example prices with written supplier and installer quotes, and enter delivery separately. Labor uses your rate per exposed face area; modeled tax applies to materials plus delivery, although actual tax treatment can differ. Changing the currency label does not convert prices. Excavation, permits, engineering, equipment and fittings need separate allowances. Confirm packaging and the final scope with your suppliers and local professionals.