Flagstone is sold by the ton, and how far a ton goes depends on the stone and its thickness. Enter the area and the coverage per ton your supplier gives; the calculator adds waste for trimming and returns the tons to order.
Flagstone formula
Tons = area × (1 + waste %) ÷ coverage per ton (sq ft)
Worked example: a 12 × 12 ft patio
- Area: 144 sq ft; with 10% waste, 158.4 sq ft.
- At 100 sq ft per ton: 1.58 tons.
Why coverage per ton varies
A ton of thin, flat stone covers much more ground than a ton of thick stone, and dense stone such as some sandstones and slates weighs more per cubic foot than others. There is no single figure that fits every flagstone, so the 100 sq ft default is only a placeholder: suppliers usually state coverage per ton for each stone and thickness, and that is the number to enter. Irregular pieces with wide joints cover a little more; tightly fitted stone covers less and creates more waste.
Tons for a range of coverages (144 sq ft, 10% waste)
| Coverage per ton | Tons |
|---|---|
| 70 sq ft | 2.26 |
| 80 sq ft | 1.98 |
| 100 sq ft | 1.58 |
| 120 sq ft | 1.32 |
| 150 sq ft | 1.06 |
Base and joints
- Flagstone on a sand or gravel base needs a compacted base; the paver calculator and sand calculator estimate those layers.
- For joints, use stone dust, polymeric sand rated for wide joints, or mortar on a concrete slab.
Questions
How many square feet does a ton of flagstone cover?
It depends on the stone and thickness; ask the supplier for the coverage of the stone you are buying.
How much extra flagstone should I buy?
About 10% for trimming is a common starting point; more for a tightly fitted pattern.
Can I buy flagstone by the pallet?
Yes. Convert the pallet weight to tons (2,000 lb per ton) and compare.
Do curved edges need more waste?
Yes. Stone cut to follow a curve leaves more offcuts, so raise the waste toward 15–20% for curved or freeform patios.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Pound and ton definitions.