Base depths follow ICPI Tech Spec 2 and 4. Frost or clay adds 2 inches.
Area 1
For edge restraint and overdig.
Advanced options
Leave 0 to use the application default.
ICPI specifies 1 in. Deeper ruts under load.
Your depth is the finished, compacted depth.
ICPI requires 6 in so edge spikes hit base, not soil.
This paver base calculator works out base gravel, bedding sand and polymeric sand to ICPI depths — including the six inches of base that must extend past every paver edge, which most calculators leave out entirely.
The short answer
A patio needs 4 inches of compacted base plus exactly 1 inch of bedding sand. A driveway needs 8 inches of base. Add 2 inches in frost or clay.
Two things most calculators miss: the base must extend 6 inches past the paver edge, and gravel loses about 20% of its depth when compacted. Both mean ordering more than the paved area suggests.
On this page
How to use this paver base calculator
Choose your application, set the climate toggle, and enter the paved area. The calculator returns base gravel in yards and tons, bedding sand, polymeric sand and the excavation depth. Four shapes:
- Rectangle — patios, pads and driveways
- L-shape — overall dimensions minus a cut-out
- Circle — fire pit surrounds and round patios
- Known area — area plus perimeter, which it needs for the overdig and edging
The header toggle switches between mild climate and frost or clay, which adds 2 inches to the base per ICPI guidance for cold or poorly draining conditions.
The five layers
A paver installation is mostly what you can’t see. From the bottom up:
| Layer | What it does | Get it wrong and |
|---|---|---|
| 1. Compacted subgrade | The native soil, compacted before anything goes on it | Everything above settles, however well built |
| 2. Geotextile fabric | Separates base from soil on clay or silt | Base sinks into soft soil over a few years |
| 3. Aggregate base | Carries and spreads the load, drains water | Rutting, rocking pavers, uneven settlement |
| 4. Bedding sand, 1 in | Levels the surface and locks paver bottoms | Too thick, it ruts. Too thin, pavers rock and chip |
| 5. Joint sand | Transfers load between pavers — this is the interlock | Pavers move independently and the field spreads |
When a patio ripples, rocks or develops low spots, the pavers are almost never the problem. It’s an under-built base, a bedding layer that was too thick, or a subgrade that was never compacted. The visible layer gets the attention and the budget; the buried ones decide whether it lasts.
Base depth by application
| Application | Mild climate | Frost or clay |
|---|---|---|
| Patio or walkway | 4 in | 6 in |
| Light vehicular | 6 in | 8 in |
| Residential driveway | 8 in | 10 in |
| Heavy vehicular | 12 in | 14 in |
These are compacted depths — the finished thickness after the plate compactor has done its work, not what you spread. The 4 inch patio figure is a minimum on well-drained, established soil; weak or wet subgrade needs more regardless of what sits on top.
The one-inch rule
This is the most common and most damaging mistake in DIY paver work, and it’s tempting because a thick sand layer makes levelling so much easier — you can screed out every dip in the base without going back to fix it.
But sand is not a structural material. Under load it displaces sideways. A two-inch bed will migrate into wheel tracks and walking lines, and the pavers follow it down. You get ruts and rocking within the first year, and the only fix is lifting the whole field.
Level with the base. Screed the sand to a consistent inch, and don’t compact it before laying — the pavers bed into it as you compact the surface.
Below about ¾ inch causes the opposite problem: pavers sit hard on the aggregate and rock against it, chipping their bottom edges. One inch, consistently, is the specification.
Why the base extends past the paver edge
Your base is not the same size as your patio. ICPI requires it to extend at least 6 inches beyond the paver edge on every side, and there are two reasons.
Edge restraint spikes need something to bite. The plastic or metal edging that holds your perimeter is spiked down every 8 to 12 inches. Those spikes must penetrate compacted base. If the base stops at the paver edge, the spikes go into soft soil, and the restraint pulls out under the first freeze-thaw cycle.
Loads spread outward. Weight applied at the surface disperses at roughly 45 degrees through the base. A paver at the very edge is loading base material that isn’t there, so the perimeter settles first.
| Paved area | Base area with 6 in overdig | Extra material |
|---|---|---|
| 10 × 10 ft — 100 ft² | 121 ft² | +21% |
| 12 × 16 ft — 192 ft² | 221 ft² | +15% |
| 16 × 20 ft — 320 ft² | 357 ft² | +12% |
| 20 × 30 ft — 600 ft² | 651 ft² | +8% |
Note that it matters most on small patios, where the perimeter is large relative to the area. A 10 × 10 ft patio needs 21% more base than its paved area suggests — and that’s before compaction.
Compaction allowance
Crushed aggregate loses roughly 20% of its volume when properly compacted. The depth in the table above is what you want when you’ve finished, so you need to order and spread about a quarter more than that.
Loose volume = Base area × finished depth × 1.20 × (1 + waste)
A 16 × 12 ft patio with 6 in overdig = 221 ft² of base
221 × 0.333 ft = 73.7 ft³ finished
× 1.20 compaction × 1.10 waste = 97 ft³ = 3.6 yd³ = 5.0 tons
A plate compactor only densifies the top few inches. Dumping 8 inches of base and running over it once leaves the bottom half loose — which is exactly the layer carrying the load. Spread and compact in layers no deeper than 4 inches, and 2 inches is better on a driveway.
Which materials
| Layer | Use | Don’t use |
|---|---|---|
| Base | Dense-graded aggregate — ¾ in minus crusher run, road base or process gravel. Angular, with fines that bind. | Clean stone with no fines, or stone screenings — they hold water and ICPI discourages them structurally. |
| Bedding | ASTM C33 concrete sand — coarse, washed, angular. | Play sand, mason sand or stone dust. Too fine; they hold water and displace under load. |
| Joints | Polymeric sand, or fine jointing sand. | Bedding sand — too coarse to sweep into narrow joints. |
| Separation | Woven geotextile over clay or silt, seams lapped 12–18 in. | Plastic sheeting. It traps water instead of letting it drain. |
How deep to excavate
Base depth + 1 in bedding sand + paver thickness
Patio: 4 + 1 + 2⅜ (60 mm paver) = 7⅜ in
Driveway: 8 + 1 + 3⅛ (80 mm paver) = 12⅛ in
Frost patio: 6 + 1 + 2⅜ = 9⅜ in
Add a slope for drainage — about ¼ inch per foot, falling away from any structure. On a 12 ft patio against a house that’s a 3 inch drop across the width, which is enough to shed water without being noticeable underfoot.
Polymeric joint sand
Joint sand isn’t cosmetic. It’s what makes an interlocking pavement interlock — load applied to one paver transfers through the joints to its neighbours. Empty joints mean each paver works alone.
| Joint width | 60 mm pavers | 80 mm pavers |
|---|---|---|
| 2 mm — tight | 113 ft² per bag | 84 ft² |
| 3 mm (⅛ in) — standard | 75 ft² | 56 ft² |
| 5 mm | 45 ft² | 34 ft² |
| 8 mm — tumbled, flagstone | 28 ft² | 21 ft² |
Coverage is per 50 lb bag, and it scales inversely with both joint width and paver thickness — a deeper paver means a deeper joint to fill. Wide joints on thick driveway pavers use several times the sand of tight joints on standard patio pavers.
Polymeric sand activates with water and hardens. Any residue left on the paver faces hardens there too, leaving a haze that is very difficult to remove. Sweep thoroughly, then blow the surface with a leaf blower on low before wetting — and follow the manufacturer’s watering sequence exactly, because over-watering flushes the binder out of the joints.
Edge restraint
Without edge restraint, a paver field spreads. Freeze-thaw and lateral load push the perimeter outward, joints open, sand washes out, and the pattern loses its geometry — typically within one to three winters.
- Spike spacing: 12 inches on centre for pedestrian patios, 8 inches for driveways, and 6 to 10 inches around curves regardless.
- Spikes must reach compacted base — which is why the base extends past the edge.
- Add two anchor spikes at each end of every connector segment.
- Concrete edge restraint is the alternative and is stronger, but it’s permanent and harder to adjust.
Paver base mistakes to avoid
- Bedding sand thicker than 1 inch. The most common cause of rutting and settlement.
- Base sized to the paved area. It extends 6 inches past every edge.
- Ignoring compaction. Order 20% more than the finished depth suggests.
- Compacting in one thick lift. The bottom stays loose.
- Skipping subgrade compaction. No base fixes soft soil underneath.
- Using stone dust or screenings as base. They hold water and can void warranties.
- Play sand for bedding. Too fine and too round — it needs to be angular C33.
- No edge restraint. The field unravels from the perimeter inward.
Frequently asked questions
How deep should a paver base be?
4 inches of compacted aggregate for a patio or walkway on well-drained soil, 6 inches for light vehicles and 8 inches for a residential driveway. Add 2 inches in freeze-thaw climates or on clay. These are compacted depths, so spread about 20% more than that.
How thick should bedding sand be under pavers?
Exactly 1 inch, screeded and not compacted before laying. A thicker layer displaces under load, causing pavers to rut and settle unevenly, usually within the first year. Below ¾ inch the pavers rock against the base and chip. Fix level with the base, never with sand.
How much gravel do I need for a paver patio?
For a 16 × 12 ft patio at 4 inches, allowing 6 inches of base past each edge, 20% compaction and 10% waste, you need about 3.6 cubic yards or 5 tons of dense-graded aggregate. The base area is 221 ft² even though the patio is only 192 ft².
Why does the base extend past the pavers?
Two reasons. Edge restraint spikes must penetrate compacted base rather than soil, or the restraint pulls out. And surface loads spread outward at roughly 45 degrees, so an edge paver needs base material beyond it. ICPI specifies at least 6 inches on every side.
How deep do I excavate for pavers?
Base depth plus 1 inch of bedding sand plus paver thickness. A standard patio with a 60 mm paver is 4 + 1 + 2⅜ = about 7⅜ inches. A driveway with 80 mm pavers is 8 + 1 + 3⅛ = about 12⅛ inches. Add slope for drainage at about ¼ inch per foot.
What kind of gravel goes under pavers?
Dense-graded aggregate — ¾ inch minus crusher run, road base or process gravel. It needs to be angular with fines that bind when compacted. Avoid clean stone with no fines, and avoid stone screenings, which hold water and are discouraged by ICPI as a structural base.
Can I use play sand under pavers?
No. Bedding sand must be ASTM C33 concrete sand — coarse, washed and angular, so the grains lock together. Play sand and mason sand are too fine and too rounded; they hold water and displace under load, which is exactly what you’re trying to prevent.
How much polymeric sand do I need?
A 50 lb bag covers about 75 ft² with standard 3 mm joints and 60 mm pavers. Coverage drops with wider joints and thicker pavers — 5 mm joints on 60 mm pavers gives 45 ft², and 8 mm joints only 28 ft². A typical patio needs two to four bags.
Do I need landscape fabric under a paver base?
Over clay or silty soil, yes — woven geotextile stops the base slowly sinking into soft subgrade, with seams lapped 12 to 18 inches. Over well-drained sandy soil it’s optional. Never use plastic sheeting, which traps water rather than letting it drain.
How much does gravel compact?
Roughly 20%, so 5 inches of loose material compacts to about 4 inches. Order and spread about a quarter more than your target finished depth, and compact in lifts no deeper than 4 inches — a plate compactor only densifies the top few inches.
Do I really need edge restraint?
Yes. Without it the perimeter spreads under freeze-thaw and lateral load, joints open, sand washes out, and the field loses its geometry within one to three winters. Spike at 12 inches on centre for patios, 8 inches for driveways, and the spikes must reach compacted base.
Can I use this paver base calculator in metric?
Dimensions are entered in feet and inches, but paver thickness is selected in millimetres since that’s how pavers are sold, and results include cubic yards alongside tons. For metric volumes, multiply cubic yards by 0.765 for cubic metres.
Standards and sources
- ICPI Tech Spec 2 — Construction of interlocking concrete pavements
- ICPI Tech Spec 4 — Structural design of interlocking concrete pavement for roads and parking lots
- CMHA (formerly ICPI/NCMA) installation guidance on base depth and bedding sand
- ASTM C33 — Concrete aggregates, the specification for bedding sand
- Aggregate weights are supplier mid-range figures; dense-graded base varies with source rock and moisture
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How this paver base calculator works out its numbers
Paved area comes from your dimensions. Base area is calculated separately, extending the overdig distance past every edge — for a rectangle that means adding twice the overdig to both length and width, and for a circle adding it to the radius. Base volume is base area times the finished depth, then multiplied by the compaction allowance and the waste factor, because the depth you enter is the compacted result rather than what you spread.
Bedding sand uses the paved area only, at the depth you set, with waste but no compaction allowance — it is screeded rather than compacted. Polymeric sand coverage starts from 75 ft² per 50 lb bag at 3 mm joints with 60 mm pavers and scales inversely with both joint width and paver thickness. Excavation depth is base plus bedding plus paver thickness.
Aggregate weights are 2,800 lb per cubic yard for dense-graded base and 2,700 for concrete sand. These vary with source rock and moisture, so treat tonnage as an estimate and expect the weigh ticket to differ.
This calculator produces quantities, not a pavement design. Base depth for vehicular applications depends on soil bearing capacity, traffic loading and drainage, and should follow ICPI Tech Spec 4 or an engineer’s design rather than a table. Subgrade condition governs everything above it.