How many bags of sand in a cubic yard?

Three sands, three jobs

Most "paver sand calculator" pages return one number for "sand". There are three materials on a paver job and they are not interchangeable:

• Bedding sand — coarse, washed concrete sand. It goes under the pavers, screeded to a nominal 1 in, and its job is to let each stone seat itself.
• Joint sand — fine sand swept into the gaps so the pavers lock together.
• Polymeric sand — joint sand with a binder that sets when wetted, which resists washout and weeds.

Put polymeric sand under the pavers and it sets solid, so you can never level a settled stone again. Sweep coarse bedding sand into the joints and it washes out in the first storm. Both mistakes are common and both are permanent.

How the bedding number is worked out

Volume is area × depth. A 10 ft × 10 ft patio at 1 in is 100 × 0.0833 = 8.3 cubic feet, or 0.31 cubic yards.

Dry concrete sand weighs about 2,700 lb per cubic yard, which is 100 lb per cubic foot, so a 50 lb bag holds 0.5 cubic feet and a cubic yard is 54 bags. Wet sand from an uncovered yard pile runs closer to 3,240 lb per yard — same volume, 20% more weight on your truck.

One inch, and not a fraction more

The ICPI / CMHA guide specification for interlocking concrete pavement says the bedding course is screeded to a nominal 1 inch (25 mm) and not exceeding 1-1/2 inches (40 mm). It also states directly: "Do not use bedding sand to fill depressions in the base surface."

That one sentence is the whole difference between a patio that stays flat and one that ripples after two winters. A thick sand bed cannot be compacted — under load it migrates sideways and the pavers above it drop. Dips belong in the aggregate base, which is compactable; the spec wants the base within ±3/8 in over a 10 ft straightedge before the sand goes down.

If your base is out by an inch, fix the base.

Polymeric sand depends on joint width, not area

The coverage printed on the bag is for a specific joint width, and this is where flat figures fall apart. Typical 50 lb bag coverage:

• 1/8 in joints — 75–100 sq ft
• 1/4 in joints — 35–50 sq ft
• 3/8 in and wider — 20–30 sq ft

Doubling the joint width nearly doubles the sand, so a bag that covers 87 sq ft of tight-jointed 4×8 brick covers about 50 sq ft of the same brick at 1/4 in. Joint depth matters too — the sand fills the full thickness of the paver, so 80 mm driveway stone takes noticeably more than 60 mm patio stone.

Buy a spare bag. Once polymeric sand has been watered in and set, you cannot open a joint back up to top it off.

What this does not include

• The aggregate base under the sand, which is the bulk of the material by weight — usually 4 in compacted for foot traffic, 6 in for vehicles.
• Edge restraint. Without it the bedding sand escapes sideways and the perimeter pavers walk outwards, whatever sand you used.