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The total wall face area to be covered.
Face area of stonework, one side only — an ashlar wall is faced and the calculation counts the units you can see. Deduct an opening large enough to matter; a run of small ones usually is not worth deducting, because cutting around them consumes what the holes saved. Measure the finished face rather than the structure behind it, which is a different size at every reveal.
The actual face length of a typical cut stone unit.
Ashlar stone often has varying sizes — use a representative average size for this estimate.
The actual face height of a typical cut stone unit.
The height of the stone as delivered, not the course height. Course height is the stone plus one joint and the calculation adds the joint itself, so entering the course height counts every joint twice and under-orders the stone. Where a wall is coursed in more than one stone height, work the commonest one and treat the rest as its own area — an average height produces a unit count that matches no course on the wall.
The mortar joint thickness between stones.
Ashlar masonry typically uses thin joints, often 1/4 to 1/2 in (6-13mm).
The depth (thickness) of the stone wall.
The bed depth of the stone — how far back from the face each unit goes — because that is what the mortar in the joints has to fill. On a solid ashlar wall it is the wall thickness; on a faced wall it is the depth of the facing stone and not the backing behind it. Entering the full thickness of a faced wall multiplies the mortar by the ratio of the two, which on a 100 mm facing in a 300 mm wall is three times too much.
Stone units needed
238 stone units
Ashlar stone units often vary in size more than manufactured brick or block — this uses a single representative size, so real stone counts may vary if your units aren't uniform.
- Coverage rate
- 1.08 units/sq ft
- Mortar volume needed
- 0.56 yd³
They open the calculator with your figures already in it
Ashlar Stone Masonry Joint Volumetrics Calculator: 238 stone units — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Coverage rate derived geometrically from nominal stone face dimensions (actual size + mortar joint width), the same method used for the Brick and CMU calculators; mortar volume from the joint gap area x wall thickness
Inputs used
- Wall Area
- 220 sq ft
- Stone Actual Length
- 16 in
- Stone Actual Height
- 7.75 in
- Mortar Joint Width
- 0.39 in
- Wall Thickness
- 11.75 in
Intermediate steps
- Coverage rate
- 1.08 units/sq ft
- Mortar volume needed
- 0.56 yd³
Confidence note: Ashlar stone units often vary in size more than manufactured brick or block — this uses a single representative size, so real stone counts may vary if your units aren't uniform.
What this calculation does not cover
- Mortar volume assumes every joint is filled solid across the full wall thickness you enter. A stone facing tied back to a blockwork inner leaf is bedded only across the stone, and a rock-faced unit with a sawn bed is bedded across the sawn part only. Enter the actual bed depth, not the wall thickness shown on the section drawing.
- No waste is added. The stone count is the bare geometric fit of one representative unit across the face area you enter: nothing for cutting at openings, quoins, jambs, reveals and cills, nothing for breakage in handling and setting, and no deduction for openings — the area you type is treated as solid stone face.
- One stone size covers the whole wall. Coursed ashlar with varying course heights, random ashlar, and the oversized units used for quoins, cills, lintels and copings are not counted separately, and no course-by-course layout is set out — part stones at course ends and wall ends are carried as fractions of the total and rounded once at the end.
- The mortar figure is the empty joint volume, not a mix quantity. It carries no allowance for mixing and board waste, does not convert to sand, cement and lime or to bag counts, and excludes any pointing or repointing mortar, which the joint face takes on top of the bedding mortar.
- This is a quantity take-off, not a design. It says nothing about wall stability, slenderness, lateral restraint, wall ties or bed-joint reinforcement, and nothing about the mortar specification — on stone the mix is chosen to suit the stone and the exposure rather than defaulted. Freestanding and retaining stone walls need design to the governing code.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-03 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Coverage rate derived geometrically from nominal stone face dimensions (actual size + mortar joint width), the same method used for the Brick and CMU calculators; mortar volume from the joint gap area x wall thickness
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