Gabion Calculator
Count the gabion baskets for a wall or revetment and the tonnes of stone fill: box size, layout along, across and up, gabion volume, filled density from porosity and the geotextile behind the wall.
How it works
boxes = ⌈length ÷ box L⌉ × ⌈thickness ÷ box W⌉ × ⌈height ÷ box H⌉ · gabion volume = boxes × box volume · filled density = (1 − porosity) × stone density · stone (t) = gabion volume × filled density
Gabions are wire-mesh baskets filled on site with hard, durable stone. The number of baskets follows from the wall dimensions rounded up to whole boxes, and the stone needed is the basket volume times the filled density — the stone’s particle density reduced by the voids between stones. With 30–40% porosity, a granite-filled gabion weighs about 1.6–1.9 t/m³ (EN 10223-8 and manufacturers’ guides). Use stone 1.5 to 2 times the mesh opening (typically 100–250 mm), place it by hand against the faces and fit internal bracing wires every 300 mm of height. Taller gravity walls are stepped and need a stability check.
Worked example
A wall 10 m long, 2 m high and 1 m thick in 2 × 1 × 1 m baskets: 5 along × 1 across × 2 high = 10 boxes, 20 m³. With granite (2.7 t/m³) and 35% voids the fill weighs 0.65 × 2.7 = 1.76 t/m³, so order about 20 × 1.755 = 35.1 t of stone, plus 20 m² of geotextile behind the wall.
Sources: EN 10223-8 Welded mesh gabion products for wall construction · US Army Corps of Engineers EM 1110-2-2502 Retaining and Flood Walls (gabion walls)
Frequently asked questions
How much stone do I need to fill a gabion?
About 1.6–1.9 tonnes per cubic metre of basket, depending on the rock and how well it is packed. A 2 × 1 × 1 m gabion takes roughly 3.5 t of granite.
What size stone goes in a gabion?
Stone should be 1.5–2 times the mesh opening — usually 100–200 mm for 80 × 100 mm mesh and 75–150 mm for mattresses — hard, angular and frost-resistant.
How tall can a gabion wall be?
Walls up to about 1–1.5 m are often built without design. Higher walls act as gravity retaining walls and are stepped back, with a base width about half to two-thirds of the height; have them checked for sliding and overturning.
Do gabions need a membrane behind them?
Yes, a non-woven geotextile between the gabions and the retained soil stops fine soil washing through the stone while letting water drain.
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This calculator is for educational purposes. Double-check important results before acting on them.