Flagstone calculator
A 12 × 16 ft patio in 1¾ to 2¼ in flagstone takes about 2.64 tons with 10% extra for cutting, roughly 2 pallets, plus 32 bags of sand for a 1 in bed.
How much a ton of flagstone covers
Flagstone is sold by weight, so the area a ton covers depends on how thick the stone is. Thin stone covers about 200 sq ft a ton; stone 2 in thick covers about 80. The calculator uses the middle of the figures six stone yards publish for each thickness. Stone varies from one quarry to the next, so if your yard gives its own coverage, enter it.
| Thickness | Used here, per ton | Published range | Weight per sq ft |
|---|---|---|---|
| About 1 in | 115 sq ft | 105 to 150 sq ft | about 17 lb |
| 1¾ to 2¼ in, dry-laid | 80 sq ft | 70 to 90 sq ft | about 25 lb |
| 2½ to 3 in | 65 sq ft | 60 to 70 sq ft | about 31 lb |
| ½ to ¾ in, set in mortar | 200 sq ft | 175 to 250 sq ft | about 10 lb |
| About 1½ in | 100 sq ft | 77 to 120 sq ft | about 20 lb |
| Area | 1 in stone | 1½ in | 1¾ to 2¼ in |
|---|---|---|---|
| 3 × 20 ft path | 0.57 | 0.66 | 0.83 |
| 10 × 10 ft patio | 0.96 | 1.10 | 1.38 |
| 10 × 12 ft | 1.15 | 1.32 | 1.65 |
| 12 × 16 ft | 1.84 | 2.11 | 2.64 |
| 16 × 20 ft | 3.06 | 3.52 | 4.40 |
| 20 × 20 ft | 3.83 | 4.40 | 5.50 |
Area: 12 ft × 16 ft = 192 sq ft
192 sq ft × 1.1 ÷ 80 sq ft a ton = 2.64 tons
Thin stone or thick
Thin flagstone, under about 1½ in, is fragile on its own and is usually set in mortar on a concrete slab. Stone 1¾ in and thicker can be dry-laid on a bed of sand over compacted gravel. Acme Sand & Gravel in Arizona recommends 1¾ in stone for a sand-set patio and 1¼ in stone over a cement base. For a mortar-set patio, work out the slab with the slab calculator and set the sand and base in this calculator to 0.
Pallets and extra
Yards sell flagstone by the ton or the pallet, and a pallet holds 1.5 to 2.25 tons. Large select pieces of 4 to 12 sq ft cover ground fast; smaller patio pieces of 1 to 4 sq ft take longer to fit. Irregular stone needs trimming to fit together, so add 10% at least. Bedford Stone advises 10 to 25%, more if you want tight joints, sort out colors or cut a lot of straight edges.
Base and joints
Under a dry-laid patio goes compacted gravel and then a sand bed; the calculator counts both at the depths you set. The paver base calculator explains base depths for patios and drives, and the crushed stone calculator works out the gravel for any size. Joints between flagstones are filled with sand, stone dust or polymeric sand. If you're comparing materials, concrete patio cost gives installed prices for a plain slab.
What you'll need
- A rubber mallet beds each stone into the sand until it stops rocking.
- A 4 ft level checks that neighboring stones sit flush and the patio falls slightly away from the house.
- A stone chisel and hand sledge trim edges so the stones fit together with even joints.
- Safety glasses keep chips out of your eyes while you trim.
- Polymeric sand fills the joints and sets when wetted, which keeps weeds and ants out.
Sources
- Coverage information, Buchheit Supply (St. Charles County, Missouri), read November 2026. Flagstone per ton: ½ to ¾ in 200+ sq ft, 1 to 1½ in 120, 1 to 1¾ in 100, 1½ to 2 in 80 to 90, 2 in 70, 2 to 3 in 60.
- Approximate coverage guide, Select Stone Supply, updated 30 July 2019. Flagstone (Ontario limestone): ½ to ¾ in 9 lb a sq ft, 250 sq ft a ton; 1 in 14 lb, 150; 1½ in 21 lb, 100; 2 in 28 lb, 80; 3 to 4 in 50 lb, 40.
- Flagstone thickness, coverage and delivery, Acme Sand & Gravel (Arizona), August 2015. Select thin (¾ to 1¼ in) 140 to 160 sq ft a ton, select regular (1 to 1¾ in) 115 to 125, 2 in heavy (1½ to 2¼ in) 80 to 90; 1¾ in stone for sand-set and 1¼ in for a cement base; pallets of 1.5 to 2 tons, about 3,500 lb.
- Approximate coverage and specifications, Jensen Sales Company (Littleton, Colorado), read November 2026. Flagstone about 110 sq ft a ton at 1 in, 90 at 1½ in and 70 at 2 in; pallets of random flagstone 1.75 to 2.25 tons.
- Estimating stone, Bedford Stone (Pennsylvania), January 2019. Irregular flagstone: ¾ in about 200 sq ft a ton, 1 in 100 to 110, 1½ in 75 to 80, 1½ to 3 in 65 to 75; allow at least 10 to 25% for waste.
- Coverage guide, Travis Equipment, read November 2026. Flagstone per ton: 1 in thick 110 to 120 sq ft, 2 in thick 70 to 80.
- Flagstone calculator, TradeStone (Texas), read November 2026. About 175 sq ft a ton at ½ to 1 in, 110 at 1 to 1½ in, 80 at 1¾ to 2¼ in, 65 at 2½ in; thin stone set in mortar on a slab, 1¾ in and thicker dry-laid on gravel and sand; add about 10%.
- Weight-Volume Relationships and Conversion Factors for Soils and Aggregates of Wisconsin (WHRP 0092-22-05), Wisconsin Highway Research Program, Michigan State University, December 2023. Measured loose and compacted weights of base aggregates, recycled asphalt and recycled concrete; tons per compacted cubic yard.
- Online store listings for bagged concrete, mortar, grout, block, rebar, mesh, gravel, sand, soil, mulch and pavers, Google Shopping results (Home Depot, Lowe's, Menards, Ace Hardware, Walmart and others), November 2026. Single-item prices by store; the calculators use the median as the default and show the range.