Paver Base Calculator for Patios Built on Expansive Clay
Enter your project dimensions
The layer that decides whether a patio is still flat in five years is the one nobody looks at. Frost goes 30 to 36 inches down through much of this state, the clay underneath swells when it takes on water and shrinks back when it dries, and a sunny February afternoon can thaw the top few inches and refreeze them by dark. Stone that is thick enough and compacted properly rides over that. The paver base calculator sizes that stone. What it will not do is talk you out of a depth that is too thin.
Base and bedding are two layers, and only one of them is here
This is the confusion that costs people a patio. Bedding sand is a screeded inch that the pavers sit down into, and nothing more. The base is the compacted structural layer under it, four inches at a minimum, and sand cannot stand in for any part of it.
An extra inch of sand feels like it does the same job on the day you lay it. It does not. Sand shifts under load, so a patio bedded thick rocks at the edges within a season and dips where the chairs go. Put depth into the stone and keep the sand at one inch. The bedding course and the joint bags are sized separately in the paver sand calculator, where the inch of bed is ordered as Mason Sand.
What clay, frost and a wet spring add to the depth you type in
Start from the use, then add for the ground.
| Where the pavers go | Compacted base depth |
|---|---|
| Walkway or garden path | 4 inches |
| Patio or seating area | 4 to 6 inches |
| Apron or parking area with cars | 6 to 8 inches |
| Clay or soft subgrade | add 2 inches, and lay fabric |
So a seating area on firm ground takes four. The same patio on the expansive clay that runs through much of the Front Range takes six, over woven geotextile. The fabric is not optional on clay. Without it, stone migrates down into the subgrade through repeated wet seasons and the base you paid for slowly becomes part of the ground.
Grade the finished base at a 2 to 3 percent fall away from the house. Snowmelt off a roof has to have somewhere to go that is not the back door.
The base footprint is six inches wider than the patio on every open side
Measure the paved area first, then add half a foot on each side that is not hard against a wall or a step. That strip is what the edge restraint gets spiked into. Restraint pinned into lawn soil instead of compacted stone pulls out, and the outside row of pavers walks away from the field over a couple of winters.
That wider rectangle is what goes into the tool, not the paver layout.
A 14 by 10 patio against the house, worked through
Hypothetical example. The patio runs 14 ft along the back wall and 10 ft out, so three sides are open. The subgrade is clay, which puts it at 6 inches.
- Choose Rectangle. Circle and Multiple areas, up to five, are the other options.
- Base footprint: 14 + 0.5 + 0.5 = 15 ft long, and 10 + 0.5 = 10.5 ft out. That is 157.5 sq ft.
- Depth 6, in inches. The field takes 0.25 to 24.
- Select the material, which applies 1.50 tons per cubic yard.
- Leave Add 10% extra for compaction & spillage ticked.
- Calculate.
- 157.5 x 6 ÷ 12 = 78.75 cubic feet
- 78.75 ÷ 27 = 2.92 cubic yards
- 2.92 x 1.50 = 4.38 tons
- With the 10% ticked: 3.21 cubic yards and 4.82 tons
Order 5 tons of Crusher Run and build it in three 2-inch lifts, misting each one lightly before the plate goes over it. Slightly damp material tightens up visibly better than dry.
Now the dig. Base plus one inch of bedding plus the paver thickness, less however much you want the surface sitting above the lawn. With standard 2 3/8 inch pavers over this 6-inch base, that is 9 3/8 inches below finished level. Mark it on a stake before you start, because digging past it means hauling soil out and then buying stone to put back in the hole you made. The dirt calculator turns that dig into the yards of spoil you have to find room for.
Why the base order weighs more than everything else on the patio
Base material is published on this site at approximately 3,000 lb per cubic yard, which is 1.50 tons. It is the heaviest of the common yard materials apart from armor stone, and the fines packed between the stones are the reason for both the weight and the way it locks up under compaction.
For comparison, a cubic yard of clean 3/4 inch stone runs about 2,800 lb and bedding sand about 2,700 lb. Clean stone is lighter because the voids between the pieces stay open, which is exactly why it drains and exactly why it will not hold a patio flat.
Reusing an old base, and when to give up on it
Relaying a patio with the same pavers is a much smaller stone order, if the layer underneath survived. Lift the pavers, sweep off the old bedding sand, and look at what is there. Firm, level, draining, no soft patches: add a fresh inch of bedding and relay. That can cut the stone order to a fraction of a new build.
Low spots, spongy sections or standing water after a rain mean the base failed, and on clay it will fail the same way again under new pavers. Dig it out, put fabric down and rebuild it at the depth in the table above.
The extra half ton that keeps the edge on stone
Leave the 10% option ticked. It covers what the compactor takes out of each lift and what gets lost spreading the pile. On a clay subgrade that is still soft from snowmelt, round the footprint up as well, because the first lift disappears into soft ground without raising the level much.
Have the stone dropped after the excavation is open, not before. A pile sitting on the lawn for two weeks leaves a dead rectangle you then have to repair, and how delivery is arranged covers what the driver needs: a firm spot with clear access to tip on, booked at checkout from your ZIP code.
Run this tool, then the bedding tool, then order both in one go. Working out the bedding layer on the morning you were going to lay pavers is how a weekend gets lost.
Common questions
Which product page do I order the base from once I have the tonnage?
Crusher Run for a patio, a walk or a small apron. A drive specified as Class 6 goes to Class 6 Road Base instead, sized in the road base calculator, since it is a different material with the same weight per yard. Quantity and delivery date are chosen on the product page.
Where do I have the stone tipped for a backyard patio?
As close to the excavation as the truck can safely get, on ground firm enough to carry it, and clear of the dig itself. Think about the wheelbarrow route before the day: a gate, a step or a soft lawn between the pile and the patio adds hours. Delivery is arranged at checkout by ZIP code.
The result gives me both tons and cubic yards. Which is the order?
Base stone is handled by the ton, so order against the tons. The cubic yard figure tells you how big the pile will be and how the lifts work out, which is what you need when you are deciding where it goes and how many passes with a wheelbarrow it means.
Is the depth I enter the loose depth or the compacted depth?
Compacted, always. Every depth on this page is the finished, rolled thickness. Loose stone takes up more room than it will after a plate compactor, so entering a loose lift leaves the base short of spec once it is rolled.
How do I estimate a round patio or a fire pit surround?
Use circle mode and enter the diameter in feet, remembering to add a foot to the diameter for the 6-inch base extension all the way round. A 9 ft circle becomes a 10 ft base footprint, or 78.5 sq ft. At 4 inches that is 26.2 cubic feet, 0.97 cubic yards, about 1.45 tons. For a circle sitting inside a rectangular patio, enter both in Multiple areas.
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The pavers get the compliments. The base earns them.
Crusher run and screenings by the ton, free delivery, ordered together with your bedding sand.