The site work division of ICFHome.ca · Building since 1979 · Insured to $2,000,000 · 705-533-1633
Armour Stone Calculator2026Tiny, Tay, Midland, Wasaga, Collingwood
Armour Stone Calculator: Pieces, Tonnes and Cost
A 20 m (66 ft) armour stone wall with 1 m of exposed face, built with 2 x 2 x 4 ft stones, takes 2 courses of 17 stones, about 34 pieces or 36 tonnes, and usually runs $10,800-$18,000 installed in 2026. Enter your own wall below to get pieces, tonnes, clear stone, filter cloth and a rough price, with the math laid out.
Updated October 2026 · Georgian Bay Siteworks, the site work division of ICFHome.ca
Insured to $2,000,000Site work division of ICFHome.caBuilding since 1979250+ projects in Simcoe County
Work out your wall
Armour stone wall calculator
Metric first. Stone sizes are named in feet because that is how quarries sell them.
Advanced: change our assumptions
Rough 2026 Ontario figures before HST. The installed rate covers stone, trucking, excavation, the clear stone base and backfill, filter cloth and machine placement.
How we calculate
- Stone size is converted from feet to metres (1 ft = 0.3048 m). A 2 x 2 x 4 ft stone is 0.61 x 0.61 x 1.22 m.
- Courses = (exposed height + buried depth) ÷ stone height, rounded up. The bottom course sits 150-300 mm below grade so the wall cannot kick out at the toe.
- Stones per course = wall length ÷ stone length, rounded up. Pieces = courses × stones per course.
- Weight per stone = height × depth × length × 2.6 t per m³ (limestone) × 0.9 shape factor. Tonnes = pieces × weight per stone.
- Clear stone = a 300 mm deep base pad, 300 mm wider than the stones, plus a 300 mm wide drainage zone behind the full wall height. Tonnes = that volume × 1.5.
- Filter cloth = wall length × (wall height + buried depth + stone depth + 0.9 m of wrap and overlap).
- Installed range = tonnes of armour stone × $300-$500 per tonne. We also show the cost per square foot of exposed face so you can compare quotes.
- Not included: engineering, permits, shoreline approvals, tree removal, hauling away excavated soil, and HST.
Over 1 metre, the rules change
A retaining wall over 1 m (1,000 mm) of exposed height next to public property, building access, or private property open to the public needs a building permit and engineered drawings. That is the Building Code, not us being fussy.
Even where the rule does not bite, a tall wall holding back a driveway or a house is an engineering question. Soil pushes harder the deeper it gets, and water behind a wall pushes harder still. The calculator will happily count stones for a 3 m wall; it cannot tell you whether that wall will stand.
Builder truth: armour stone walls rarely fail because a stone was too small. They fail because water had nowhere to go. The clear stone and filter cloth behind the wall are the cheap part that does the real work.
Shoreline walls are a different animal
Placing stone at or near the water on Georgian Bay or an inland lake usually needs approvals before any machine moves. Depending on where you are, that can include the township, the conservation authority (Wasaga Beach and Collingwood are in NVCA territory, Tiny has no conservation authority), and provincial or federal agencies for work in or near the water.
Approvals take time, and fines for unapproved work are real: the NVCA can fine up to $50,000 for work in a regulated area without a permit. Read our NVCA permit guide and the permits and approvals page before you book stone.
Choosing a stone size
2 x 2 x 4 ft
About 1.1 t each. Good for garden walls, terraces and walls up to about 1 m. Easy to place with a mid-size excavator.
2 x 3 x 5 ft
About 2 t each. The deeper stone resists tipping better. A common choice for walls holding a driveway or a slope.
3 x 3 x 6 ft
About 3.6 t each. Big, heavy and stable, often used on shorelines and taller engineered walls. Needs a bigger machine and good access.
- Deeper is better than taller. A stone that is deeper front to back than it is tall is much harder to push over.
- Step each course back slightly. A small setback per course leans the wall into the hill instead of away from it.
- Stagger the joints like brickwork, so no joint runs straight up the wall.
- Plan the access. A tri-axle of armour stone and an excavator need a firm path to the wall. Lawns, septic beds and wet ground are not paths.
For full price ranges and what moves them, see our armour stone retaining wall cost guide.
Send us the wall and we will price it properly
Length, height, a few photos and what the wall is holding back. That is enough for a ballpark, and we will tell you up front if it needs an engineer.
Related guides
Frequently Asked Questions
How many armour stones do I need for a 20 m wall?
With 2 x 2 x 4 ft stones and 1 m of exposed height, about 17 stones per course and 2 courses, so roughly 34 pieces or 36 tonnes. Bigger stones mean fewer pieces but more tonnes.
How much does an armour stone weigh?
Limestone weighs about 2.6 tonnes per cubic metre. Allowing for irregular shapes, a 2 x 2 x 4 ft stone is about 1.1 tonnes, a 2 x 3 x 5 ft about 2 tonnes, and a 3 x 3 x 6 ft about 3.6 tonnes.
How much does an armour stone wall cost in Ontario?
As a rough 2026 range, we use 300-500 dollars per tonne of stone installed, which includes trucking, the base, drainage stone, filter cloth and placement. Access, height and shoreline work move it most.
Do I need a permit for an armour stone wall?
A retaining wall over 1 m of exposed height next to public property, building access or private property open to the public needs a permit and engineered drawings. Shoreline work usually needs approvals regardless of height.
Why does a wall need clear stone and filter cloth?
Water behind a wall adds a lot of pressure. Clear stone gives the water a path out, and filter cloth keeps soil from clogging that stone over time.
How deep should the first course be buried?
We usually set the bottom course 150-300 mm below finished grade on a compacted clear stone pad, so the toe of the wall cannot slide out.