TryBuildCalcFlagstone Patio Calculator (Tons & Coverage by Thickness)
Size your flagstone patio by weight instantly.
🕒 Last updated: September 22, 2026
Inputs
Sand-Set builds up a base course, bedding sand, pavers/flagstone, and swept joint sand — held at the edges by a separate edge restraint.
Aggregate Base
ℹ️ICPI/CMHA cite 4 in as the minimum pedestrian patio base over well-drained soil. Step up to 6 in for clay-rich/poor-draining soil or a frost-prone climate.
Bedding / Stone Dust
ℹ️Irregular flagstone commonly sits on a thicker 1-2 in setting bed to accommodate the stone's own thickness variation.
ℹ️Bulk delivery is standard; bagged is only practical for a small patio.
Flagstone
ℹ️Density drives coverage-per-ton — a denser stone at the same thickness covers less area per ton.
Joint Fill
ℹ️Joint depth is set to your surface material's own thickness.
Geotextile Fabric & Edge Restraint
Standard practice between subgrade and base — prevents soil migration into the base.
Edge restraint is required for an interlocking sand-set system to perform correctly — pick "No" only if a suitable restraint already exists or will be quoted separately.
Cost
Flagstone Needed
1.54
tons (Bluestone, 1.5" thick)
Aggregate Base Needed
3.347 tons
4" deep
Patio Area
140
sq ft (13.01 m²) — 14 x 10 ft
Installation Method: Sand-Set (Flexible / Interlocking) — Surface: Natural Flagstone
Aggregate Base
Quarry Process (QP) — US driveway base, 4" deep
Installed volume: 1.728 cu yd
Order volume (incl. 15% compaction + 8% waste): 2.147 cu yd
Weight: 3.347 tons
Bedding / Stone Dust
Concrete Sand (ASTM C33) — recommended for bedding, 1" deep
Order volume (incl. 10% waste): 0.475 cu yd
Weight: 0.721 tons
Flagstone
Bluestone, 1.5" thick (160 lb/cu ft)
Order area (incl. 10% cut/breakage waste): 154 sq ft
Coverage: ~100 sq ft per ton
Tons needed: 1.54
Joint Fill
Polymeric/joint sand, 1" wide
Volume (incl. 12% waste): 1.96 cu ft
Bags needed: 4 (~50 lb each)
Geotextile Fabric
Area (+10% overlap): 154 sq ft
Rolls needed (12.5 x 360 ft each): 1
Edge Restraint
Steel / Aluminum Edge Restraint — holds curves well, longest-lasting
Length needed: 48 linear ft
Assumptions Used
Rectangular residential patio, pedestrian loads only (never vehicular). Sand-Set: an aggregate base (15% compaction + 8% waste), a screeded bedding course (10% waste, no compaction since it is installed loose), swept-in joint sand (12% waste for repeated dry fill/compact passes), and a required edge restraint around the full perimeter to keep the interlocking system from spreading apart. Flagstone (Bluestone) is quantified by weight (tons), not a fabricated per-unit count, using its own density and a 10% cutting/breakage allowance; its joint volume is approximated as a fraction of surface area, a standard simplification for irregular-stone jointing. This calculator computes material quantities only — it does not verify subgrade compaction adequacy, drainage slope, local frost-depth requirements, or structural design for an unusual soil or loading condition.
Approximate results for planning only. Verify with a professional.
Diagram simplified for clarity (not to scale) — layer band heights reflect relative thickness, not exact scale.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Patio/Paver Materials Calculator.
Flagstone is bought by weight, not by a paver count
Unlike a concrete paver, irregular natural flagstone is sold and priced by weight (tons) or area coverage, never by a fabricated per-unit count. Coverage per ton depends directly on the stone's own density and thickness — a thicker slab of the same stone weighs more per square foot and covers less area per ton.
This page defaults to a 14 x 10 ft patio (140 sq ft) using 1.5 in thick Bluestone on a sand-set bed — edit the inputs above to match your own patio size, flagstone type, and thickness.
Patio/Paver Materials Calculator Formula: How Is It Determined?
Your patio area, installation method, and surface material combine into a full material takeoff, with a different formula path for each branch of the sand-set/mortar-set x pavers/flagstone matrix.
Step 1 — Patio Area
Area = Length x Width
Entered directly as a single rectangle.
Step 2a — Sand-Set: Base Course
Base Volume = Area x Base Depth
Order Volume = Base Volume x (1 + 15% compaction) x (1 + 8% waste)
Base depth is a pedestrian-only figure (4-6 in) per ICPI/CMHA patio guidance — materially shallower than a driveway's vehicular-load base.
Step 2b — Mortar-Set: Concrete Slab
Slab Volume = Area x Slab Thickness (skipped entirely if mortaring onto an EXISTING slab)
Order Volume = Slab Volume x (1 + 5% waste)
A new slab is 4-6 in thick per CMHA mortar-set guidance; an existing, sound concrete patio can be used directly with no new slab material.
Step 3 — Bedding Course or Mortar Setting Bed
Sand-Set: Bedding Volume = Area x Bedding Depth x (1 + 10% waste)
Mortar-Set: Mortar Bed Volume = Area x Mortar Bed Depth x (1 + 10% waste), then Bags = Order Volume / Bag Yield
Bedding sand/stone dust is installed loose (no compaction allowance); a mortar bed is troweled to a nominal thickness and bagged in whole units.
Step 4a — Concrete Pavers
Order Area = Area x (1 + Layout Pattern Waste %)
Paver Count = Order Area / Paver Unit Area
Layout pattern waste ranges 5-13% depending on cut geometry — the same formula this site's Paver Driveway Calculator uses, since the underlying cutting-waste geometry doesn't change for pedestrian loads.
Step 4b — Natural Flagstone
Order Area = Area x (1 + 10% cutting/breakage waste)
Tons = Order Area x Thickness x Stone Density / 2000
Flagstone is quantified by WEIGHT, not a fabricated per-unit count — coverage-per-ton is derived directly from the stone's own density and thickness.
Step 5 — Joint Fill
Rectangular units: Volume per sq ft = 144 x (1/W + 1/L) x Joint Width x Joint Depth
Flagstone: Volume = Area x Joint Area Fraction x Joint Depth
Concrete pavers use exact rectangular joint geometry; flagstone's irregular joints are approximated as a fraction of surface area that scales with joint width (a standard simplification for irregular-stone jointing takeoffs).
Step 6 — Cost
Line Cost = Order Quantity (bags/tons/sheets/bars/sq ft, as actually purchased) x Unit Price
Total = Sum of every line item relevant to your selected installation method
Every cost line is priced off the actual PURCHASED unit — never the bare theoretical volume — and only line items relevant to your selected Sand-Set/Mortar-Set branch are included in the total.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value |
|---|---|
| Patio Size | 14 x 10 ft (140 sq ft) |
| Installation Method | Sand-Set |
| Surface Material | Bluestone |
Step 2a — Base Course
| Calculation | Result |
|---|---|
| 140 sq ft x 4/12 ft, +15% compaction +8% waste | 2.147 cu yd (3.347 tons) |
Step 3 — Bedding Sand
| Calculation | Result |
|---|---|
| 140 sq ft x 1/12 ft, +10% waste | 0.475 cu yd |
Step 4b — Flagstone
| Calculation | Result |
|---|---|
| 154 sq ft x 1.5/12 ft x 160 lb/cu ft / 2000 | 1.54 tons |
Step 5 — Joint Fill
| Calculation | Result |
|---|---|
| 1.75 cu ft, +12% waste | 1.96 cu ft (4 bags) |
Figures above are rounded for display; the real quantities are always calculated from full, unrounded values.
Therefore, a 140 sq ft (14 x 10 ft) Sand-Set patio using 1.54 tons of Bluestone needs 2.147 cu yd of base and 0.475 cu yd of bedding, plus 4 bags of joint fill.