Flagstone Calculator: How Many Tons for Your Patio or Path

Enter the length and width of your patio, walkway or path in feet, then pick the stone thickness you plan to buy. That's it - the calculator returns how many tons of flagstone to order, with a 10% allowance for breakage and trimming already included.

Open More options if you want to type a total square footage instead of dimensions, switch to metric (meters and tonnes), choose a specific stone such as bluestone or Arizona sandstone, change the waste allowance, or enter a price per ton to see the material cost. For an L-shaped or curved patio, split it into rectangles, add up the square footage, and use the total-area option.

Flagstone is sold by weight, not by area, so the question every buyer asks is "how many square feet does a ton of flagstone cover?" The answer depends almost entirely on thickness. A typical flagstone weighs about 165 pounds per cubic foot, which works out to roughly 13.75 lb per square foot for every inch of thickness. At the most common 1.5-inch thickness, each square foot weighs about 20.6 lb, so one ton (2,000 lb) covers roughly 97 square feet. Go up to 2-inch stone and the same ton covers only about 73 square feet.

That is why a 1-inch flagstone calculator result can be half the tonnage of a 2-inch one for the same patio. Thin flags (1 inch) are normally set in a mortar bed over concrete, while 1.5 to 2-inch stone is the usual choice for dry-laid patios on a gravel and sand base. Stone type matters less - sandstone is about 12% lighter than average, slate a little heavier - but the calculator lets you account for it under More options.

Area = length x width (sq ft)
Area with waste = area x (1 + waste %)
Weight per sq ft (lb) = stone density (lb/ft³) x thickness (in) / 12
Tons = area with waste x weight per sq ft / 2,000

Coverage per ton = 2,000 / weight per sq ft. In metric, tonnes = area (m²) x (1 + waste) x thickness (m) x density (kg/m³) / 1,000, using 165 lb/ft³ ≈ 2,643 kg/m³.

How much flagstone for a 10x10 patio? 100 sq ft plus 10% waste = 110 sq ft. At 1.5 inches thick, 110 x 20.625 lb = 2,269 lb, or 1.13 tons - order 1.5 tons.

How many tons of flagstone for a 12x12 patio at 2 inches? 144 sq ft x 1.10 = 158.4 sq ft. 158.4 x 27.5 lb = 4,356 lb = 2.18 tons - order 2.5 tons.

Flagstone for a 3 ft x 30 ft garden path, 1-inch stone: 90 sq ft x 1.10 = 99 sq ft. 99 x 13.75 lb = 1,361 lb = 0.68 tons - one ton covers it with stone to spare.

10x20 patio, 1.5-inch flagstone: 200 sq ft x 1.10 = 220 sq ft. 220 x 20.625 lb = 4,538 lb = 2.27 tons, about two pallets.

Buy by the half ton. Most stone yards sell flagstone by the ton or by the pallet and will split to the half ton. The calculator rounds your order up to the next half ton so you don't come up short mid-project.

Irregular stone needs more waste. Random-shaped flagstone leaves gaps and needs trimming to fit edges; use 15% waste. Square-cut or pattern-cut stone can drop to 5%.

Thickness varies within a pallet. A pallet sold as 1.5-inch may run from 1 to 2 inches. If the yard quotes a range, use the midpoint.

Don't forget the base. A dry-laid patio usually sits on 4 inches of compacted gravel plus 1 inch of sand - estimate those separately with the gravel and sand calculators.

Check pallet weight. Pallets typically hold 1 to 1.5 tons; ask your supplier, since the pallet count here assumes 1.5 tons each.