Flagstone Calculator — Square Feet to Tons
Flagstone is sold by the ton, but you plan a patio by the square foot. Enter your area and the stone thickness, and this calculator converts it to tons — including a waste allowance for breakage and fitting.
How to use this calculator
- Measure the patio or path length and width in feet.
- Enter the stone thickness — thinner stone covers more area per ton.
- Adjust density for your stone type if you know it; sandstone is about 150 lb/cu ft.
- The result includes 10% extra for breakage and the irregular fitting of natural stone.
The formula
Flagstone is priced by weight, so we convert your area to tons.
Volume (cubic feet) = area × thickness (in) ÷ 12. Weight (lb) = volume × density. Tons = weight ÷ 2,000.
Add about 10% for breakage and the cutting and fitting that irregular natural stone requires.
Worked example
A 12 ft × 10 ft patio with 1.5 in sandstone (150 lb/cu ft).
Area = 12 × 10 = 120 sq ftVolume = 120 × (1.5 ÷ 12) = 15 cubic feetWeight = 15 × 150 = 2,250 lb → 1.13 tonsWith 10% waste ≈ 1.24 tons
A 120 sq ft patio in 1.5 in sandstone needs about 1.24 tons of flagstone.
Frequently asked questions
How many square feet does a ton of flagstone cover?
It depends on thickness. A ton of 1.5 inch flagstone covers roughly 100–120 sq ft; 1 inch stone covers more (≈150 sq ft) and 2 inch stone less (≈75 sq ft).
How thick should flagstone be?
For dry-laid stone on a sand or gravel base, use 1.5–2 inches so pieces stay stable. For flagstone mortared over a concrete slab, 1–1.5 inches is enough.
How much extra flagstone should I order?
Order about 10% extra. Natural stone breaks and needs cutting to fit, and having spare pieces lets you match thickness and color across the patio.