Flagstone Calculator
Flagstone is sold by the ton, and how far a ton goes depends on how thick the stone is: thin patio stone covers roughly twice the area of thick slabs. Enter the patio size, the thickness you are buying and a waste allowance for the tons of flagstone, plus the crushed stone base and sand bed a dry-laid patio sits on.
What you'll need
As an Amazon Associate I earn from qualifying purchases.
33ft. Galvanized Steel Landscape Edging (10-Pack) – 40" Metal Edging for Landscaping with 11 Stakes, Hammer-in Metal Landscaping Edging for Yard Pathway & Flower Beds – Lawn Edge for Garden Design
$69.99
Check price on Amazon
FEED GARDEN Landscape Staples 6 Inch 50 Pack, Galvanized Garden Stakes
$9.99
Check price on Amazon
BlumeTrec 8"x8" Steel Tamper with 48" Handle, Heavy Duty Hand Compactor Tool for Leveling Soil, Gravel, Sand, Asphalt, Ground, Paver, Driveway, Garden, Yard and Blacktop Repair
Save 9%
$39.99List Price:: $43.99
Fire Pit Spark Screen, Fire Pit Screen 36 Inch Round with Handle & Poker
$75.99
Check price on AmazonPrices and savings as of Sep 30, 2026, 4:34 AM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
Why thickness decides the tonnage
A ton of stone is a fixed volume, so thin stone spreads further. Ironside Stone Works, a Montana stone supplier, quotes roughly 150–180 sq ft per ton for thin ½–1 inch flagstone, 100–120 sq ft for 1–2 inch patio stone and 75–100 sq ft for 2–3 inch slabs; Select Stone Supply puts 2 inch stone at about 80 sq ft per ton. Natural flagstone varies piece to piece, which is why the calculator gives a range rather than one number.
Worked example: 20 × 10 ft patio in 1–2 in stone
| Step | Working | Result |
|---|---|---|
| Area + 10% waste | 200 × 1.10 | 220 sq ft |
| Flagstone | 220 ÷ 120 to 220 ÷ 100 | 1.8–2.2 tons |
| 4 in crusher run base | 200 × 4 ÷ 12 ÷ 27 × 1.5 | 2.47 yd³ = 3.7 tons |
| 1 in sand bed | 200 × 1 ÷ 12 ÷ 27 × 1.35 | 0.62 yd³ = 0.83 tons |
Dry-laid on a base
The usual DIY method is dry-laying: excavate, compact a crushed stone base, screed a thin bed of sand or stone dust, then bed each stone and sweep the joints full. The paver base calculator goes deeper on the base layers, the polymeric sand calculator fills tight joints, and a gravel patio is the cheaper alternative if the budget will not stretch to stone.
Get the Gravel & Stone Calculator app for Android
Estimate gravel, stone, sand, and mulch on the job site, save projects, and share quantities with your supplier.
Building something else? Try our sister calculators
Smart Roofing Calculator
Free roof replacement cost estimates by material and pitch.
Smart Decking Calculator
Deck cost, boards, joists, and stair estimates.
Smart Fencing Calculator
Fence cost by material and linear footage.
Smart Tile Calculator
Tile quantity, grout, and thinset estimates.
Smart Insulation Calculator
R-value, batt count, and blown-in coverage.
Smart Decking Calculator
Android app — deck cost, boards, and framing on site.
Smart Drywall Calculator
Android app — drywall sheets, mud, and tape estimates.
Smart Sod Calculator
Android app — sod rolls, pallets, and coverage.
Smart Insulation Calculator
Android app — R-value and batt coverage.
Smart Tile Calculator
Android app — tile, grout, and thinset quantities.
Smart Fencing Calculator
Android app — fence cost estimates on the go.
Frequently asked questions
- How much area does a ton of flagstone cover?
- It depends on thickness. Ironside Stone Works quotes roughly 150–180 sq ft per ton for thin ½–1 in stone, 100–120 sq ft for 1–2 in patio stone, and 75–100 sq ft for 2–3 in slabs. Select Stone Supply puts 2 inch flagstone at about 80 sq ft per ton.
- How much flagstone do I need for a 10x20 patio?
- 200 sq ft plus 10% waste is 220 sq ft. At 100–120 sq ft per ton for 1–2 in patio stone that is 1.8 to 2.2 tons. Under it, a 4 inch crusher run base is 2.47 cubic yards (3.7 tons) and a 1 inch sand bed is 0.62 cubic yards (0.83 tons).
- How much extra flagstone should I order?
- At least 10%, and up to 25% for irregular stone or tight joints — the range suppliers such as Ironside Stone Works recommend. Irregular pieces rarely fit without trimming, and it is hard to match a second delivery.
- What do you put under flagstone?
- For a dry-laid patio, a compacted crushed stone base such as crusher run and a thin sand or stone-dust bed to seat each piece. The depths are inputs above; the paver base calculator covers the same layers for pavers.
- Is flagstone sold by the ton or square foot?
- Most stone yards sell natural flagstone by the ton or by the pallet, because each piece is a different size. Convert your patio area to tons with the supplier's coverage rate, then round up to their pallet size.
Related calculators
All calculators →
Pea Gravel Calculator
Pea gravel quantity and cost for patios, play areas, dog runs, and garden beds.
Open calculator →
River Rock Calculator
River rock quantity and cost for beds, dry creek features, and decorative borders.
Open calculator →
Decomposed Granite Calculator
Decomposed granite quantity for paths, patios, and xeriscape areas, with or without stabilizer.
Open calculator →