Flagstone Patio Calculator
Estimate the tons of flagstone and cost for a patio from its size and the coverage per ton, with waste included.
How it works
area = length × width · tons = area ÷ coverage per ton · add 10% for waste · cost = tons × price per ton
Flagstone is sold by weight, so the estimate turns the patio area into tons using the stone’s coverage rating — how many square feet one ton lays at a given thickness. Thicker or denser stone covers less area per ton, so use the supplier’s figure for your specific stone; 100–150 square feet per ton spans most 1–2 inch flagstone. Add roughly 10% because irregular pieces leave gaps and cutting produces offcuts.
Worked example
A 16 × 12 ft patio is 192 sq ft. At 120 sq ft per ton that is 192 ÷ 120 = 1.6 tons; with 10% waste, about 1.76 tons. At $350 per ton the stone runs roughly $616, before base gravel and sand.
Frequently asked questions
How much does a ton of flagstone cover?
Around 100–150 square feet for typical 1–2 inch patio stone; thicker wall stone covers far less. Always use the coverage number your supplier gives for the exact stone, since density and thickness vary a lot.
Do I need a base under flagstone?
Yes. A dry-laid patio wants 4–6 inches of compacted gravel topped with a bedding layer of sand or stone dust. That base is what keeps the stones from rocking and settling.
Why add 10% waste for flagstone?
Natural flagstone is irregular, so you cut and shape pieces to fit tight joints, and some pieces break. Extra stone also lets you pick pleasing color and shape combinations rather than using every scrap.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.