Flagstone Calculator

How much flagstone do I need?

Flagstone is sold by the ton, and a ton covers less area the thicker the stone. Divide the area by the coverage per ton for your thickness, then add about 10 percent for cuts and breakage.

Acme's own example: a 15 × 15 ft patio (225 sq ft) in 1¾ inch stone at 120 sq ft per ton takes 1.88 tons, before waste. With 10% extra that is 2.07 tons.

Flagstone is flat stone split along its bedding planes, usually a sandstone made of quartz and feldspar. It is used for patios, walkways, steps and flooring. Suppliers also sell bluestone, limestone and other flat stone in the same way.

How to use the flagstone calculator

The flagstone calculator divides your area by the coverage per ton for the stone you pick. The "How we calculated this" panel shows each step, and the PDF report keeps them for your stone yard.

Step 1: Measure the patio in square feet

Multiply length by width. For curves or an L shape, break the patio into rectangles and add them up in the square footage calculator.

Step 2: Pick the stone thickness

Choose thin, regular, heavy or patio stone. Each one uses the mid-point of Acme's coverage range. If your yard quotes a different figure, use theirs.

Step 3: Add waste and read the order

Set 5, 10 or 15 percent for fitting. You get tons, pallets and the weight. Enter your price per ton to see the stone cost.

Flagstone coverage per ton by thickness

From Acme Sand & Gravel's flagstone sheet:

Select Stone Supply gives the same idea: one ton of 2 inch flagstone covers about 80 sq ft, so a 25 × 30 ft patio (750 sq ft) takes about 9.5 tons. Thin patio-gauge stone sits toward the high end of the range, and thick standup stone toward the low end.

Random flagstone vs square-cut flagstone

The base, sand and joints under and between the stone

The stone is only part of the order. A dry-laid flagstone patio is a layered build, and the material under the stone is often a bigger volume than the stone itself.

Earth Stone Rock's rule of thumb: a 100 sq ft patio needs about 1.2 cubic yards of base and 0.3 cubic yards of bedding sand on top of the stone tonnage. Work out the base with the paver base calculator and the sand with the paver sand calculator.

Joints and spacing

Flagstone is laid with gaps that you fill later. Wider joints mean fewer stones cover the same footprint, so a relaxed layout stretches the order a little further than tight joints.

Fill the joints with sand, decomposed granite or pea gravel. For a joint that locks, use polymeric sand. See the polymeric sand calculator for the bag count.

Worked examples

A 10 × 10 ft entry patio (100 sq ft) in patio-gauge stone at about 110 sq ft per ton needs a little under 1 ton. With 10% extra that is about 1 ton. In thicker stone at 90 sq ft per ton it needs 1.1 tons before the extra, according to Earth Stone Rock.

A 15 × 15 ft patio in 1¾ inch stone at 120 sq ft per ton takes 1.88 tons, or 2.07 tons with waste. On Acme pallets of about 1.75 tons, that is just over one pallet.

Flagstone types and weight

Most flagstone is sandstone, and yards also sell bluestone, limestone and other flat stone. Each has its own color, thickness and price. Ask your supplier for the coverage per ton of the exact stone, because the flagstone calculator can only use the figure you give it.

Select Stone Supply notes that a cubic foot of limestone weighs about 165 lb, so any stone sold by weight can be converted from volume. Denser stone weighs more per square foot, which lowers the coverage per ton.

Flagstone for walls and veneer

The flagstone calculator is for flat surfaces such as patios and walkways. A wall is estimated by its face area instead. Select Stone Supply gives building stone with a 4 inch bed depth at about 50 lb per sq ft, so a ton covers about 40 sq ft of wall face. Wall stone with an 8 inch bed covers about 20 sq ft per ton.

How a flagstone patio goes together

1. Excavate deep enough for the base, the sand and the stone.
2. Compact the base in a 4 inch layer of road base or crushed stone.
3. Screed the bedding sand about 1 inch deep.
4. Set the stones with even joint spacing and fit the cut pieces last.
5. Fill the joints with sand, decomposed granite, pea gravel or polymeric sand.

Flagstone patio or stepping stones?

For a full patio surface, flagstone laid tight is the usual choice, and the flagstone calculator gives the tonnage. For a path across a lawn or bed you do not need full coverage. Stepping stones set with planted gaps use far less stone, and you size them by counting steps instead of covering an area.

Flagstone cost

Price depends on the stone, the region and the delivery, so the flagstone calculator does not guess it. Enter the price per ton from your yard and it multiplies by the tons you need. Square-cut stone is priced per square foot instead. Add the base, sand and edge restraints to get the full project cost.

Common flagstone ordering mistakes

• Using one coverage for every stone. A ton of thin stone covers far more than a ton of thick stone.
• Forgetting waste. Cut pieces and breakage add up to about 10% of the order.
• Ordering the stone only. The base, bedding sand and joint material are separate orders.
• Thin stone on sand. It can crack under load. Match the thickness to how you set it.

Before you order flagstone

Measure the patio, pick the thickness, and let the flagstone calculator give you tons and pallets with 10% extra. Confirm the coverage per ton with your yard, then order the base, bedding sand and joint fill along with the stone. Keep the flagstone calculator PDF to compare quotes.

Frequently asked questions