How to calculate flagstone
Example: a 12 ft × 14 ft patio is 168 sq ft. With 10% extra (185 sq ft) and standard 1½–2 inch stone at about 95 sq ft per ton, you need about 1.95 tons.
Coverage per ton
| Thickness | Typical coverage per ton | Good for |
|---|---|---|
| 1–1½ in | ~110–130 sq ft | Set in mortar on concrete |
| 1½–2 in | ~90–100 sq ft | Dry-laid patios and paths |
| 2–3 in | ~60–80 sq ft | Stepping stones, heavier use |
Wider gaps between stones (for moss or gravel joints) stretch coverage further; tight joints use more stone.
Base
For a dry-laid patio, use about 4 inches of compacted gravel base and a 1-inch bed of sand or stone dust. The calculator estimates both.
Frequently asked questions
How many square feet does a ton of flagstone cover?
Roughly 90–100 sq ft for 1½–2 inch stone, more for thinner stone and less for thicker.
How much flagstone for a 10 × 10 patio?
100 sq ft plus 10% extra ≈ 1.2 tons of 1½–2 inch flagstone.
What thickness of flagstone should I use?
1½–2 inches for dry-laid patios and paths; thinner stone needs a concrete base and mortar.
What goes under flagstone?
Typically 4 inches of compacted gravel base and 1 inch of sand or stone dust for setting the stones.
Related calculators
These figures are estimates for planning only. Material weights and coverage vary by supplier, moisture and compaction. Always confirm quantities and prices with your supplier before ordering. See our terms & disclaimer.