Flagstone Calculator
Enter your patio or path dimensions and depth to find out how much bedding sand, stone dust, or crushed stone base you need. Get cubic yards, tons, and an estimated cost.
Measure straight across the widest point.
Adjust depth below if needed.
Covers spillage and compaction. 5–10% is normal.
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Bags or bulk delivery?
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Coverage & weight
Material profile
For a 15 ft × 10 ft patio (150 sq ft) at a 1.5 in bedding depth, you need 0.76 cubic yards of bedding sand with a 10% waste allowance — about 1.03 tons. That’s roughly 42 bags at 0.5 cu ft each, or $126.50 in bulk plus delivery.
How much bedding sand do common flagstone projects need?
These figures use bedding sand at 2,700 lb per cubic yard and don’t include a waste allowance.
| Project | Depth | Cubic yards | Tons |
|---|---|---|---|
| Small seating area (8×8 ft) | 1.5 in | 0.30 cy | 0.40 tons |
| Walkway (3×40 ft) | 1.5 in | 0.56 cy | 0.75 tons |
| Medium patio (12×16 ft) | 1.5 in | 0.89 cy | 1.20 tons |
| Large patio, full base (20×20 ft) | 5 in | 6.17 cy | 8.33 tons |
| Fire pit surround (10 ft diameter) | 1.5 in | 0.36 cy | 0.49 tons |
| Full-base pathway (4×30 ft) | 5 in | 1.85 cy | 2.50 tons |
Flagstone bedding and base material options
| Type | Weight per yd³ | Best for | Drainage |
|---|---|---|---|
| Bedding sand under flagstone | 2,700 lb | Dry-lay flagstone bedding | Good |
| Stone dust bedding | 2,800 lb | Firm flagstone bedding | Poor |
| Crushed stone sub-base | 2,700 lb | Base under bedding layer | Moderate |
Figures are for dry material. Wet or freshly delivered material can weigh noticeably more.
How to calculate flagstone you need
- Measure the area Multiply length by width (or use the circle/triangle/border shape option) to get square footage.
- Choose your depth Pick bedding-only (1.5 in) or a full base-plus-bedding system (5 in total), or enter a custom depth.
- Calculate the volume Convert depth to feet and multiply by area to get cubic feet, then divide by 27 for cubic yards.
- Add your waste allowance Multiply by 1 plus your waste percentage (10% is typical) to cover cuts and settling.
- Convert to tons Multiply cubic yards by your material’s density (2,700–2,800 lb/yd³) and divide by 2,000.
Worked example
Here’s the math for a 15 ft × 10 ft patio with a 1.5 in bedding sand layer and the default 10% waste allowance.
- Area (15 ft × 10 ft)150 sq ft
- Depth1.5 in (0.125 ft)
- Volume150 × 0.125 = 18.75 cubic ft
- Cubic yards with 10% waste18.75 ÷ 27 × 1.10 = 0.76 cy
- Tons needed (bedding sand, 2,700 lb/yd³)0.76 × 2,700 ÷ 2,000 = 1.03 tons
- Bulk cost + delivery1.03 × $50 + $75 = $126.50
- Bagged alternative (0.5 cu ft bags)42 bags × $5.50 = $231.00
Recommended depth by project
| Project | Recommended depth | Notes |
|---|---|---|
| Project type | Depth | Notes |
| Bedding sand under flagstone | 1–1.5 in | Standard dry-lay depth over a compacted base |
| Stone dust bedding | 1–2 in | Sets firmer than sand; drains poorly in wet climates |
| Full base + bedding (patio) | 4–6 in total | 3–4 in compacted crushed stone plus 1–1.5 in bedding |
| Stepping stone path | 1 in | Sand bed set directly on prepared soil |
| Driveway-grade flagstone | 6–8 in total | Deeper compacted base needed for vehicle loads |
| Fire pit / edging surround | 1.5–2 in | Extra depth helps stones sit level around curves |
Bags or bulk delivery?
Bagged sand and stone dust typically come in 0.5 cubic foot bags and cost more per cubic yard than bulk delivery. Bulk is almost always cheaper once you need more than about half a cubic yard, but bags avoid a delivery minimum and let you buy exactly what you need. For do-it-yourself patios under 100 sq ft, bags are often the simpler choice.
- Small jobs (under 1 cy)Bags are usually easier — no delivery fee, no leftover pile
- Medium jobs (1–3 cy)Compare bagged total cost against bulk + delivery before deciding
- Large jobs (3+ cy)Bulk delivery is almost always cheaper per ton
Common mistakes
- Skipping the compacted baseFlagstone set directly on soil shifts, sinks, and heaves with frost
- Using stone dust where drainage mattersStone dust compacts hard but sheds water poorly in wet, low-lying areas
- Ignoring flagstone thickness variationNatural stone varies 1–3 in thick; a deeper sand bed lets you level irregular pieces
- Forgetting waste for cuts and edgesIrregular shapes and border cuts eat more material than a straight layout
- Mixing bedding materials mid-projectSwitching between sand and stone dust changes how the patio settles over time
- Under-ordering for a full base systemBase + bedding depth (4–6 in total) needs far more material than bedding alone
What this calculator assumes
Adjust your result if your project differs from these.
- Bedding sand is calculated at 2,700 lb per cubic yard unless you choose stone dust (2,800 lb/yd³) or crushed stone base (2,700 lb/yd³).
- Depth is entered in inches and converted to feet before the volume calculation.
- The default 10% waste allowance covers irregular cuts and settling; increase it for complex patio shapes.
- Bagged material assumes standard 0.5 cubic foot bags.
- Delivery is priced as a flat fee, not per ton.
- Results are estimates — always round up and confirm with your supplier before ordering.
Common questions
How much sand do I need under flagstone?
For a bedding-only layer, plan on 1 to 1.5 inches of sand across the patio area. A 150 sq ft patio at 1.5 in needs roughly 0.76 cubic yards (about 1 ton) with a 10% waste allowance.
Should I use sand or stone dust under flagstone?
Sand drains better and is easier to adjust, but stone dust compacts firmer and holds stones in place better on slopes. In wet or poorly draining sites, sand is usually the safer choice.
How deep should the base be for a flagstone patio?
A full base-plus-bedding system runs 4 to 6 inches total — typically 3–4 in of compacted crushed stone topped with 1–1.5 in of bedding sand or stone dust.
Can I lay flagstone directly on dirt?
Not recommended. Without a compacted base, stones sink unevenly and shift with rain and frost. At minimum, use a bedding layer over compacted soil.
How much does flagstone bedding material cost?
At $50 per ton, a typical 150 sq ft patio bedding layer runs about $50–$130 depending on depth, plus a flat delivery fee.
Do I need landscape fabric under flagstone?
Yes, for most installations. Fabric between the soil and base layer helps keep base material from mixing into the subgrade and slows weed growth.
How many bags of sand do I need for flagstone?
Based on 0.5 cubic foot bags, a 150 sq ft patio at 1.5 in depth needs about 42 bags with a 10% waste allowance.
What's the difference between flagstone base and bedding layers?
The base layer (crushed stone) provides drainage and load support; the bedding layer (sand or stone dust) sits on top and lets you level individual stones.
How much extra should I order for waste?
10% is a reasonable default for straightforward rectangular patios. Increase it to 15–20% for curved edges, borders, or lots of stone cutting.
Does flagstone thickness affect how much sand I need?
Yes. Thicker, more irregular stones need a deeper, more forgiving bedding layer to level out — budget closer to 1.5–2 in instead of 1 in.
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Project
| Shape | — |
| Dimensions | — |
| Depth | — |
| Area | — |
| Material | — |
| Waste allowance | — |
Volume & weight (incl. waste)
| Cubic yards | — |
| Cubic feet | — |
| Weight | — |
| Tons (rounded up) | — |
Shopping list
| Bulk order | — |
| Bagged alternative (0.5 cu ft) | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes uniform depth and standard dry material densities. Confirm quantities with your supplier before ordering.