Flagstone Tonnage & Cost Calculator
Thin (¾" – 1¼") [~110 sq ft/ton]
Standard Patio (1″ – 1½") [~90 sq ft/ton]
Medium (1½" – 2″) [~75 sq ft/ton]
Heavy/Step (2″ – 2½") [~60 sq ft/ton]
Approximate coverage based on typical sandstone density.
Recommended: 15% for irregular shapes.
Base Area:
0 sq ft
Total Area (w/ Waste):
0 sq ft
Est. Coverage Rate:
0 sq ft/ton
Flagstone Needed:
0.00 Tons
Estimated Material Cost:
$0.00
How to Calculate Flagstone Needs
Planning a flagstone patio, walkway, or stepping stone path requires accurate material estimation to avoid running out of stone mid-project or overspending on heavy pallets. Unlike manufactured pavers which are sold by the square foot, natural flagstone is typically sold by weight (tonnage).
1. Calculate Your Project Area
Measure the length and width of the area you intend to pave.
Formula: Length (ft) × Width (ft) = Area (sq ft).
If your patio has an irregular shape, break it down into smaller rectangles, calculate the area for each, and add them together.
2. Choose Your Thickness (Coverage Rate)
The most critical factor in a flagstone calculator is the "Coverage Rate," which is how many square feet one ton of stone will cover. This depends entirely on the thickness of the stone:
- Thin (¾" – 1¼"): Covers approx. 100-120 sq. ft. per ton. Best for concrete overlays (wet set).
- Standard (1″ – 1½"): Covers approx. 80-100 sq. ft. per ton. Ideal for sand-set patios and walkways.
- Heavy (2″ +): Covers approx. 50-70 sq. ft. per ton. Used for dry-stack walls, stepping stones, or heavy traffic areas.
3. Account for Waste (The "Jigsaw" Factor)
Flagstone is organic and irregular. Fitting pieces together requires cutting and chipping, creating waste material that cannot be used.
Recommended Waste Factors:
- 10%: For very large, open areas with wide joints (gaps).
- 15-20%: For standard patios requiring moderate cutting.
- 25%+: For projects with many curves, tight joints, or specific shape requirements.
4. Flagstone Installation Tips
Once you have your tonnage calculated using the tool above, remember these installation essentials:
- Sub-base: For a stable patio, excavate 6 inches down. Install 4 inches of compacted crushed gravel (road base) followed by 1-2 inches of bedding sand.
- Joint Material: The gaps between stones can be filled with polymeric sand (hardens to prevent weeds), decomposed granite, or decorative pea gravel.
- Grading: Always slope your patio away from your home foundation (approx. ¼ inch drop per foot) to ensure proper drainage.