Paver Calculator — pavers, bedding sand and base

The document everyone cites has been renumbered, and it is not a standard. The Interlocking Concrete Pavement Institute merged with the National Concrete Masonry Association to form the Concrete Masonry & Hardscapes Association, and what the internet still calls “ICPI Tech Spec 2” is now CMHA Tech Note PAV‑TEC‑002‑22, Construction of Interlocking Concrete Pavements. Worth knowing before you quote it at a contractor: CMHA prints its own disclaimer on these documents saying the content is not intended for use or reliance upon as an industry standard, certification or specification. The base depths on this page are a trade association's recommended practice. They are the best published figures there are, and they are not code.

The base is bigger than the patio, and that is where the estimate goes wrong. CMHA's edge restraint document, PAV‑TEC‑003‑22, gives its own rule of thumb: an edge restraint spiked into a flexible aggregate base needs the base to extend past it by about the base thickness. Its worked example is a 6 in base extending 6 in. A 10 by 12 ft patio is 120 ft² of pavers, but on a 4 in base the base runs 10 ft‑8 by 12 ft‑8, which is 135 ft². That is 13% more base, more excavation and more compaction than the paver area implies, and it is the line most calculators simply do not have. The field above is editable because you may be restrained by an existing wall or a poured curb instead, in which case the base does not have to run past that edge at all.

The base thickness is a compacted thickness, so this is not what you order. PAV‑TEC‑002‑22 asks for at least 98% of standard Proctor density for pedestrian areas and residential driveways, and 98% of modified Proctor for vehicular areas. That is the same percentage against a different test, and a materially higher density. The volume above is therefore the volume in place after compaction. CMHA publishes no loose‑to‑compacted conversion, so this page refuses to invent one: ask your supplier what their material shrinks by, or work it through the excavation calculator, which handles swell and shrinkage properly. Multiplying this figure by a swell factor you found on a forum is how a delivery arrives short.

The bedding sand is specified uncompacted, so do not add a compaction allowance. The wording is a screeded, uncompacted nominal 1 in. Plate‑compacting the pavers pulls that down by roughly a quarter of an inch, and the pavement settles about another eighth over time, but both of those are elevation allowances. They tell you where to set the screed rails relative to the finished level, not how much sand to buy. Add them to the volume and you have bought the same sand twice. Note also that sand cannot rescue a bad base: CMHA's guide specification says outright that the installer cannot correct deficiencies in the base surface with extra bedding sand, and holds the base to plus or minus 3/8 in under a 10 ft straightedge.

Polymeric sand has no default, and anyone who gives you one is guessing. Techniseal's own data sheet for SmartSand publishes 60 to 120 ft² per 50 lb bag for narrow joints and 25 to 40 ft² for wide joints. That narrow‑joint figure is a two‑fold spread inside one category from one brand. Sakrete's PermaSand publishes 30 to 45 ft² per 40 lb pail, and only at one stated condition: a quarter‑inch joint with a 2 in paver. The bag in your hand is the only authority, which is why the field above starts empty. Worth noticing too that CMHA's joint width for sand‑set interlocking pavement is 1/16 to 3/16 in, much narrower than the joints polymeric coverage figures are usually quoted against.

Measure a paver rather than typing the name of one. A unit sold as “4 by 8” is a nominal description, and the module it lays on is the unit plus one joint. If you enter the catalogue size as the paver size and then add a joint on top of it, every module comes out one joint too big and the count comes out short. On a 120 ft² patio with a 1/8 in joint that is about 25 pavers. The defaults above are a measured unit, not a catalogue name. Take a tape to one and to the joint you actually intend to lay.