How to Use the Retaining Wall Block Calculator
A segmental retaining wall (SRW) is built by stacking interlocking concrete blocks — like Keystone or Versa-Lok units — into a gravity or reinforced wall face, and getting the block count right before ordering avoids both material shortages and costly re-orders. This calculator multiplies wall length by height to get total wall area, then divides by the exposed face area of the block you're using (width x height) to get the raw block count.
Real jobsites need more blocks than the raw math suggests, because of corner cuts, curves, breakage during handling, and manufacturing tolerance. A waste factor — typically around 5% — is applied on top of the raw count so you order enough the first time.
Block dimensions vary by manufacturer, so enter the actual face width and height of the SRW block you plan to use. Taller walls or those carrying surcharge loads usually need geogrid reinforcement and a drainage design behind the wall, which this calculator doesn't cover — have a civil engineer review the design before construction on anything beyond a low garden wall.
The count here is for the standard face blocks only. Cap units for the top course and any corner-specific units are typically sold separately and should be ordered in addition to this quantity. Behind the wall, drainage gravel and a perforated drain pipe are also part of a proper SRW installation, so plan for that material alongside the block order to avoid delays.
Frequently Asked Questions
Corner cuts, curves, breakage, and dimensional variance mean you'll need more blocks delivered than the raw calculation. A waste factor of around 5% is standard to cover that gap.
Enter the actual face width and height of the segmental retaining wall (SRW) block you're using. Dimensions vary by manufacturer (Keystone, Versa-Lok, and others), so check the product spec sheet before ordering.