A paver patio is really three layers: a compacted gravel base, a thin bed of sand, and the pavers themselves. This calculator sizes all three at once and adds up the cost, so you order the right amount the first time instead of making a second trip to the yard. Here is how the numbers come together and where projects most often go wrong.
Why the waste percentage matters
Almost no patio is a perfect multiple of whole pavers. Every edge that isn't a clean grid line forces a cut, and each cut wastes part of a paver — plus a few always crack during handling or compaction. A 10% allowance covers a straight running-bond or stack-bond pattern. Diagonal and herringbone layouts create far more partial pieces at the borders, so they need 15% or more. It is cheaper to buy a handful of extra pavers than to special-order a second batch later and risk a color mismatch between dye lots.
Base prep is the part that lasts
The gravel sub-base is what carries the load and lets water drain, and it is the layer most DIYers skimp on. For a patio or walkway, plan on 4–6 inches of compacted crushed stone; driveways and soft or clay soils want more. The thin sand layer on top — about an inch — is only for leveling and seating the pavers, not for support. Compact the gravel in lifts with a plate compactor before screeding the sand; loose base is the number-one cause of sunken, lippy pavers a year later. Note that bulk gravel is sold by the ton and weight varies with moisture and stone type, so treat the tonnage here as a planning figure and confirm with your supplier.
Sand vs. gravel — two different jobs
It is easy to conflate the layers, but they do different work. Base gravel is the structural, draining sub-base. Bedding sand is the leveling course the pavers sit in. A third material, joint sand, is swept into the gaps after laying to lock the pavers together — polymeric joint sand hardens and resists weeds and washout. This tool sizes the base and bedding layers and lets you fold joint sand, edge restraints, delivery, or labor into the "Extra costs" field so the total reflects the whole job, not just the pavers.