Calculate flagstone weight from patio area and thickness using typical stone densities like sandstone, bluestone or slate, plus weight per square foot.

1.5 in is a typical patio flagstone thickness (most are 1–2 in). Enter yours if known.

Editable planning value; selecting a preset replaces it.

Optional settings
Blank = 0%. Added to installed weight, not a fraction discarded.

Blank omits the count. Pallet weights vary by supplier; ask yours.

Flagstone Weight Formula

The following formula is used to calculate the Flagstone Weight. 

Order weight = A × T × D × (1 + w / 100)

Variables:

  • Order weight is the stone to order (lb), including the selected extra allowance
  • A is installed coverage area (ft²), or length × width
  • D is stone density (lb/ft³), using supplier data or an approximate planning preset
  • T is average thickness (ft); w is extra allowance (%) relative to installed weight

Multiply coverage area, average thickness and density for installed stone weight, then multiply by (1 + extra allowance / 100) for order weight. Densities vary by quarry product; presets are approximate planning assumptions. This excludes bedding and does not certify a floor or vehicle load.

How to Calculate Flagstone Weight?

The following steps outline how to calculate the Flagstone Weight.

  1. First, determine installed coverage area (length × width).
  2. Next, choose supplier density or an approximate planning preset.
  3. Next, enter average stone thickness with the correct unit and any optional extra allowance.
  4. Next, use order weight = area × thickness in feet × density × (1 + allowance / 100).
  5. Finally, calculate the Flagstone Weight.
  6. After inserting the variables and calculating the result, check your answer with the calculator above. 

Example Problem:

Use the following variables as an example problem to test your knowledge.

Coverage area = 10 ft × 14 ft = 140 ft²

Average thickness = 2 in = 1/6 ft; assumed density = 145 lb/ft³; extra allowance = 10%

Order weight = 140 × (2/12) × 145 × 1.10 ≈ 3,721.67 lb (1.86083 US short tons). Inverse modes find coverage or average thickness using available order weight and the same allowance convention.