Paver Base Calculator for a Patio Built on Fox Valley Clay
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Tight, limy clay near the bay and along the lower Fox holds water for days after rain and cannot drain at all while the subsoil is still frozen. A patio built on it moves unless the layer underneath is thick enough and the water has somewhere to go. So the useful way into a paver base calculator is not a definition of base stone. It is one job, measured and priced in tons, with the depth chosen for that ground.
An 18 by 11 patio on clay, worked end to end
Say the patio runs eighteen feet along the back of the house and comes eleven feet out into the yard. Hypothetical, but the arithmetic is real.
The base does not stop where the pavers stop. It runs six inches past every open edge, because edge restraint has to be pinned into compacted stone rather than lawn soil. The house side is closed, so the footprint grows on three sides only:
- Length: 18 plus 6 inches at each end = 19 feet
- Width: 11 plus 6 inches on the open side = 11.5 feet
- Base area: 19 x 11.5 = 218.5 square feet
Clay subgrade means six compacted inches rather than four, with woven geotextile under the stone so it cannot work its way down into wet ground.
- 6 inches is 0.5 feet, so 218.5 x 0.5 = 109.25 cubic feet
- 109.25 divided by 27 = 4.05 cubic yards
- 4.05 x 1.50 = 6.1 tons
- With the ten percent ticked: 4.46 cubic yards, about 6.7 tons
Order seven tons. The same patio on sandy outwash at four inches would take about 4.1 tons, which is the clearest illustration on this page of what subgrade is worth.
The skirt of stone outside the pavers belongs in the length box
That skirt is the single most common thing left out of a base order, and on a small patio it is about half a ton. Count the edges that end in lawn or planting and add half a foot to each, then measure. A walk with lawn on both sides gains a foot of width and a foot of length. A patio in a corner between house and garage gains on two sides only.
Checklist before the shapes go in:
- Mark the base footprint on the grass with paint, not the paver outline.
- Decide the depth from the subgrade, not from the patio size.
- Note whether the fall runs away from the house. Two to three percent, set in the base.
- Keep the walk and the patio as separate areas if their depths differ.
Compacted inches in the depth box, and a dig that is deeper again
Type the thickness the layer will be after the plate compactor has been over it, in two-inch lifts, misting each one. The hole is a different number entirely: base depth, plus an inch of bedding sand, plus the paver thickness, less whatever reveal you want above grade. A common patio paver at two and three eighths of an inch over a six-inch base means digging about nine and a half inches down.
Mark that on a stake and check it as you dig. Going too deep costs twice, once to cart the soil away and again to buy stone to bring the level back up.
The rest of the form is short:
- Shape. Rectangle, circle, or multiple areas, up to five.
- Size. Feet for length and width, or a diameter for a round seating area.
- Depth. Inches, 0.25 to 24.
- Material. The select list. It is what changes the weight.
- Extra. The ten percent tick for compaction and spillage, on by default.
- Result. Cubic yards, tons and cubic feet, with an emailed quote if you want one.
Why four cubic yards of base arrives as six tons
The base rows on this site publish at roughly 3,000 lb per cubic yard, which is 1.50 tons, and that is the figure behind the numbers above. Clean stone of a similar size is lighter, near 2,800 lb or 1.40 tons, because there are no fines filling the voids. Screenings sit between them at about 2,900 lb, 1.45 tons.
Checking it by hand takes four steps: depth in inches over twelve, times the square footage, over twenty-seven, times one and a half.
Traffic bond carries the patio, Screenings only level it
Traffic bond is the dense-graded base the whole four to six inches should be built from. Screenings belong on top of it as a thin leveling skim, or not at all. Used as the structure they trap water and shift under load, and a patio that lifts in March rarely lifts because of the pavers.
On soft or peaty ground, a coarse layer of Breaker Run goes under the traffic bond and gets calculated as its own layer at its own depth. Bedding sand is a separate order again, held to a strict inch and sized on the paver sand calculator; a deeper sand layer will never make up for a base that is short.
Stone that cannot be added later, once the pavers are down
Base is the one layer that cannot be revisited once pavers are down. Leave the ten percent ticked, then round up on top of it. Half a ton of stone left over is worth far more than a compactor sitting idle while a second delivery is arranged.
Time the dig for the window between the end of the thaw and the first hard freeze, and have the stone arrive after excavation rather than before, since a pile parked on the lawn for two weeks leaves a dead rectangle behind. When the tonnage looks right, set the quantity and the date at checkout, where delivery is arranged by ZIP code. The delivery page covers what the truck needs at your end, and odd shapes can go through the contact page with dimensions marked.
Common questions
Does the six-inch skirt of base really need buying, or is that overcautious?
It needs buying. Edge restraint spikes go through the base, and a restraint pinned into soil moves the first time the ground heaves, taking the outside course of pavers with it. On an eighteen-foot patio that skirt is about half a ton of stone and it is the cheapest half ton in the job.
Base underneath and bedding sand above. How do I split one order?
Run this tool for the stone at four to six compacted inches, then the paver sand tool for the bedding at one inch, and put both quantities on the same delivery date. They sit on different weight rows, 1.50 tons a yard against 1.35, so a single calculation covering both would be wrong for one of them.
The patio has a curved front edge sweeping out to a fire ring. What do I measure?
Square the curve off into a rectangle that runs to the midpoint of the sweep, then add the fire ring seating area as a circle using multiple areas. Base stone is forgiving of that treatment because anything spare gets raked into the transition where the two shapes meet.
We are lifting an old patio and the base under it still looks sound. How much do I need?
Clear the old bedding sand off and test it. If it is level, firm underfoot and sheds water, you need bedding sand only, which is a small fraction of a new build's material. Low spots, soft patches or standing water mean the base comes out too, and leaving a failed one in place just puts the same fault under new pavers.
What actually happens if the base order lands a ton short?
You finish thin somewhere, usually at the far edge where nobody is watching the string line, and that thin strip is where the patio dips in the second spring. A short base cannot be topped up later without lifting pavers, so round up rather than risk it.
Related calculators
The pavers get the compliments. The base earns them.
Crusher run and screenings by the ton, free delivery, ordered together with your bedding sand.