The pavers are the part you see — the gravel base and sand bed under them are the part that decides whether your patio is still flat in three years. The math for both is simple, but the depths change with what's rolling over the patio. Here's how to size the base, the bedding, and the joint sand without overpaying or coming up short.

The base formula

All paver-base material — gravel, sand, anything sold by the yard — uses the same volume math:

cubic yards = (area_ft² × depth_in) ÷ 324

The 324 converts inch-feet to yards (12 in × 27 ft³ per yd³). It's the same divisor for any landscape material sold by the yard.

Example: a 120 ft² patio with a 4 in compacted gravel base. (120 × 4) ÷ 324 = 1.48 yd³ of base. Plus a 1 in sand bed: (120 × 1) ÷ 324 = 0.37 yd³. Total order: about 1.85 yd³ — but order 2 yd³ to cover compaction loss and edges.

The paver base & sand calculator does this for you and adjusts depth by project type.

How deep should the gravel base be?

Base depth scales with what's rolling on top:

  • Patio (foot traffic only): 4 in compacted gravel
  • Walkway (foot traffic, occasional wheelbarrow): 4 in
  • Light driveway (passenger vehicles): 8 in
  • Heavy driveway (trucks, RVs): 10-12 in

The numbers come from ICPI residential install guidelines. The jump from patio to driveway is large because vehicle weight cycles the base material — every pass squeezes air out and the surface drops. Underbuilt driveway bases dip into ruts within two years.

Frost-heave climates (anywhere with freezing winters) push these numbers higher. In Minnesota or Vermont, add 2 in to every depth above. The Frost Action chapter of any state DOT spec book has the depth-per-zone table if you want the local number.

Compaction — the step DIYers skip

Loose gravel poured 4 in deep compacts to about 3 in. If you don't compact, the patio settles unevenly under foot traffic and rocks visibly within a season. The fix:

  • Lay the gravel in 2 in lifts (passes), not all at once
  • Compact each lift with a plate compactor (rentable for $40-60/day)
  • 3-4 passes per lift, perpendicular directions
  • Wet the gravel lightly before compacting — water lubricates the angular pieces into place

Order an extra 15-20% of base gravel beyond the calculator number to cover the compaction loss. The math returns finished volume, not loose-load volume.

Bedding sand vs joint sand — they're not the same

Bedding sand is the 1 in screed layer that the pavers sit on. Use clean, sharp concrete sand(ASTM C-33) or stone dust. Avoid mason sand or play sand — they're too fine and pump out from under the pavers when saturated.

Joint sandis what fills the gaps between pavers after they're laid. Two choices:

  • Plain mason sand: $5-8 per 50 lb bag. Washes out in heavy rain. Weeds germinate in it within a year.
  • Polymeric joint sand: $25-35 per 50 lb bag. Has polymer binders that activate when wetted and set up like soft mortar. Resists washout, weeds, and ant colonization for 5-10 years.

Polymeric coverage is roughly 75 ft² per 50 lb bag for typical 3/8 in joints with standard pavers. For tight 1/8 in joints with slabs, coverage doubles to ~150 ft²/bag. Manufacturer charts on the bag label give the exact number for your paver size.

What pros do differently

Order base in bulk, not bags. A yard of gravel from a landscape supply yard is $30-50 delivered. The same volume in 60 lb bags from a home center is $200+ and 30 trips to the car. Bulk delivery requires somewhere to dump it — driveway works.

Buy bedding sand and base gravel from the same yard. They deliver together, and the yard rounds up to the nearest half-yard at no extra charge. Splitting orders across home center and yard adds shipping each time.

Tarp the polymeric sand. One unexpected rain on an unswept polymeric job locks the sand into a hard crust on the paver faces that takes pressure-washing to remove. Tarp the patio for 24 hours after sweeping in the sand and before the activation watering.

Quick FAQ

Can I use sand instead of gravel for the base? No. Sand doesn't compact into a stable structure under load — it just shifts. Gravel base, sand bedding. Always.

How much does a yard of gravel weigh? About 2,400-2,800 lb. A standard pickup bed legally hauls about half a yard. Get it delivered.

Polymeric sand on a slope?Yes — it's actually better than plain sand on slopes because it doesn't wash downhill in the first heavy rain.

Get the paver count in the same trip. Use the paver calculator to size the pavers themselves so you can pick up everything from the supply yard in one delivery.