Paver Patio Calculator

What this calculator does

Patio dimensions and paver size go in. Out comes the paver count with waste applied, base stone in cubic yards and in tons, bedding sand in both units, bags of polymeric jointing sand, linear feet of edge restraint, and a total at your prices.

Note that pavers are counted, base is weighed, and jointing sand is bagged. That unit switching is not a quirk of this calculator — it is how the industry sells the materials, and translating between them at the supply yard is where most patio budgets go wrong.

The joint is part of the paver

Here is the detail that makes paver counts come out three or four percent short.

A “4 by 8” holland stone is 4 by 8 inches. Laid with a 1/8-inch sand joint, each unit actually occupies 4.125 by 8.125 inches of patio — 33.5 square inches rather than 32. That is 4.30 pavers per square foot instead of 4.50.

Wait — that is fewer pavers, not more. Correct: accounting for the joint lowers the count. Which is why the error runs the other way from what people expect. Estimating without joints tells you to buy more than you need, and on tight-butted units with no joint at all, the nominal number is right.

Either way, the calculator uses the module including the joint, which is the honest number.

The base is the patio

Every paver failure that is not a drainage failure is a base failure.

Pavers themselves are enormously strong in compression and do essentially nothing structurally as a system — they distribute load into the layer beneath them and rely on that layer to be flat, compacted and stable. So:

Depth. Four to six inches of compacted aggregate for foot traffic. Eight to twelve for anything a car drives on. In a climate with meaningful frost, depth is set by frost heave rather than load, and locals will tell you a number larger than either of those.

Material. Dense-graded crushed aggregate — the mix of stone sizes and fines that locks together when compacted. Not clean stone, not pea gravel, not “gravel” generically. Ask for road base or the local equivalent by name.

Compaction in lifts. Three inches at a time, plate compactor, both directions. Dumping six inches and compacting once compacts the top two and leaves four inches of loose material under your patio.

Slope. One-eighth to one-quarter inch of fall per foot, away from the house, built into the base and carried through the pavers. Flat patios hold water, and water is how the base gets destroyed.

One inch of bedding sand. One.

Screeded coarse sand, one inch thick, laid over the compacted base and never compacted itself before the pavers go down.

The temptation — and it is a strong one, because it saves an hour of base work — is to use bedding sand to smooth out an uneven base. Do not. Sand is not structural. Where it is thick, pavers settle; where it is thin, they do not, and the resulting ripple is permanent and highly visible in raking light.

Screed to one inch off a flat base. That is the whole technique.

Jointing sand and what it does

After the pavers are down and compacted into the bedding, sand gets swept into the joints and vibrated in. This is not cosmetic: the sand in the joints is what makes an interlocking pavement interlock. It transfers load laterally between units, so a wheel on one paver is carried by a dozen.

Polymeric sand — sand with a binder that sets when wetted — resists washout and weed growth far better than plain sand, at a few times the price. Coverage runs roughly 40 square feet per 50-pound bag on standard joints, which is what this calculator uses. Wide joints or thicker pavers use considerably more.

Edge restraint

Every edge that is not against a building or a curb needs restraint: plastic or aluminium edging spiked into the compacted base, sitting against the outer face of the perimeter pavers.

Without it, the perimeter row creeps outward under traffic. The joints open, the jointing sand escapes, the interlock is lost, and the failure marches inward one row at a time. It is a slow failure and a completely avoidable one, and the material is inexpensive — perimeter feet, priced per foot, which is what the calculator returns.

What this leaves out

• Excavation and spoil. The excavation calculator turns the cut volume into truckloads, including the swell that makes dug soil occupy more space than it did in the ground.
• Geotextile fabric between subgrade and base. Cheap, and essential in clay soils where base stone otherwise disappears into the subgrade.
• Compaction equipment rental.
• Cutting. A masonry saw or splitter, and blades.
• Drainage. A patio against a house needs the water to have somewhere to go.
• Labour. Which on paver work is the large majority of a contractor’s price.

For loose material instead of units, the gravel calculator handles the volume-to-tons conversion directly, and the concrete calculator covers a poured slab if you would rather not lay anything by hand at all.