Overview
Decorative work is usually shallow — 40-50mm — while gabion baskets fill by volume, so measure the basket voids instead of the ground area.
How the calculation works
Decorative stone weight = area × dressing depth × planning density, with lighter ornamental gravels near 1.5 t/m³ and slate near 1.6 t/m³.
Coverage inverts the sum: one tonne at 1.5 t/m³ laid 50mm deep covers about 13.3 m².
Gabion stone is sized to stay in the mesh — often 100-200mm — and is ordered by the basket volume in m³ times the packed density (about 1.5 t/m³).
Worked example
A border 6m × 1.5m is dressed with decorative gravel 50mm deep.
Area = 9 m². Volume = 0.45 m³. Weight = 0.45 × 1.5 = 0.68 tonnes.
With 10% allowance, order 0.75 tonnes — one 850kg bulk bag covers it.
Decorative gravel at a glance
- Planning density1.50 t/m³
- Typical range1.30–1.70 t/m³
- CategoryDecorative
- CompactionUsually not applied
- SourcePlanning value; decorative products vary widely by stone type
- Reviewed2026-08-16
Planning values for typical UK supplies; your supplier product data takes precedence.
Decorative gravel coverage guide
| Depth | Area per tonne | Area per 850kg bag | Weight per m² |
|---|---|---|---|
| 25mm | 26.7 m² | 22.7 m² | 38 kg |
| 40mm | 16.7 m² | 14.2 m² | 60 kg |
| 50mm | 13.3 m² | 11.3 m² | 75 kg |
| 75mm | 8.9 m² | 7.6 m² | 113 kg |
| 100mm | 6.7 m² | 5.7 m² | 150 kg |
| 150mm | 4.4 m² | 3.8 m² | 225 kg |
Computed from a 1.50 t/m³ planning density on level ground.
Assumptions and accuracy
Ornamental products vary most in density: glass, flint, quartz and limestone chippings all differ.
Coverage assumes an even depth over a level, membrane-covered base.
Confirm coverage claims with your supplier — product-specific figures always take precedence.
Planning density values
Use supplier product data whenever available. These figures are planning defaults shared by every calculator on the site.
| Material | Category | Planning density | Typical range | Compaction |
|---|---|---|---|---|
| MOT Type 1 | Sub Base | 2.20 t/m³ | 2.00–2.30 t/m³ | Relevant |
| MOT Type 3 | Sub Base | 2.10 t/m³ | 1.90–2.20 t/m³ | Relevant |
| Recycled Type 1 | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| 6F2 / 6F5 crushed aggregate | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Road planings | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Sharp sand | Sand | 1.60 t/m³ | 1.50–1.70 t/m³ | Usually no |
| Building sand | Sand | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| Kiln-dried sand | Sand | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| 10mm pea shingle | Gravel | 1.60 t/m³ | 1.40–1.70 t/m³ | Usually no |
| 20mm gravel / shingle | Gravel | 1.60 t/m³ | 1.40–1.70 t/m³ | Usually no |
| Decorative gravel | Decorative | 1.50 t/m³ | 1.30–1.70 t/m³ | Usually no |
| Slate chippings | Decorative | 1.60 t/m³ | 1.40–1.80 t/m³ | Usually no |
| Gabion stone | Gravel | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| Self-binding gravel | Gravel | 1.90 t/m³ | 1.80–2.10 t/m³ | Relevant |
| Crushed concrete | Recycled | 1.90 t/m³ | 1.70–2.10 t/m³ | Relevant |
| Limestone scalpings | Sub Base | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Ballast | Sand | 1.70 t/m³ | 1.60–1.80 t/m³ | Usually no |
| Generic aggregate | General | 1.70 t/m³ | 1.50–2.20 t/m³ | Usually no |
How to use this calculator
- Measure the border, bed or feature area.
- Enter 40-50mm for decorative dressings, or your gabion basket depth for basket fills.
- Pick the stone type — densities range noticeably between products.
- Use the custom area field for curved or irregular beds.
When stone is commonly used
Decorative stones finish borders, rockeries, water features and Japanese-style gardens; gabion stone fills wire baskets for retaining walls and seats; larger cobbles edge ponds and paths.
Frequently asked questions
How much decorative stone do I need?
At 50mm deep, one tonne of typical decorative gravel covers about 13 m². Multiply your area by 75-80kg per m² at that depth, then add a small allowance.
How do I calculate gabion stone?
Measure each basket's length × width × height in metres to get m³, then multiply by about 1.5 t/m³ for packed stone. A 1m × 0.5m × 0.5m basket holds 0.25 m³ — roughly 375kg of gabion stone.
What depth for decorative stone?
40-50mm gives full coverage over a membrane without wasting stone; deeper layers are only needed on slopes or for weed suppression in deep beds.
How do I keep decorative stone in place on a slope?
Use continuous edging, keep the dressing to 40–50mm over a membrane, and choose larger or angular stone on gradients. Steeper banks suit stepped terraces or 40mm slate rather than pea gravel.
References and source notes
- Decorative aggregate coverage and density ranges from UK supplier product data (planning values).