Overview
Site measurements are volumetric; merchants sell by weight. This converter prices the gap.
How the calculation works
Weight (tonnes) = volume (m³) × density (t/m³) — the same planning densities used across this site.
Volume first: for an area and depth, m³ = area × depth-in-metres; a 20 m² patio at 50mm is 1.0 m³.
Then multiply: 1.0 m³ of gravel ≈ 1.6 t to order; of Type 1 ≈ 2.2 t. Density, not volume, drives the invoice.
Worked example
A trench 6m × 0.5m × 0.3m needs 0.9 m³ of 10mm pea shingle surround.
Weight = 0.9 × 1.6 = 1.44 tonnes.
With a 10% allowance, order 1.58 tonnes — two 850kg bulk bags.
20mm gravel / shingle at a glance
- Planning density1.60 t/m³
- Typical range1.40–1.70 t/m³
- CategoryGravel
- CompactionUsually not applied
- SourcePlanning value based on typical UK 20mm shingle bulk densities
- Reviewed2026-08-16
Planning values for typical UK supplies; your supplier product data takes precedence.
20mm gravel / shingle coverage guide
| Depth | Area per tonne | Area per 850kg bag | Weight per m² |
|---|---|---|---|
| 25mm | 25.0 m² | 21.3 m² | 40 kg |
| 40mm | 15.6 m² | 13.3 m² | 64 kg |
| 50mm | 12.5 m² | 10.6 m² | 80 kg |
| 75mm | 8.3 m² | 7.1 m² | 120 kg |
| 100mm | 6.3 m² | 5.3 m² | 160 kg |
| 150mm | 4.2 m² | 3.5 m² | 240 kg |
Computed from a 1.60 t/m³ planning density on level ground.
Assumptions and accuracy
Planning densities assume typical UK supplies; confirm your product's figures for firm orders.
Wet material weighs more per m³; deliveries in rain run heavier.
For the reverse conversion use the tonnes to cubic metres converter.
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
- Work out or measure the volume in cubic metres.
- Enter it and select the material.
- Read the tonnage to order, then add your supplier's price per tonne for a cost estimate.
- Use the shape calculator above the converter if you only have dimensions.
When aggregate is commonly used
Pricing grab-lorry or tipper loads quoted in m³, converting trench and soakaway volumes into orderable weights, and sanity-checking supplier quotations against measured voids.
Frequently asked questions
How many tonnes in a cubic metre of gravel?
About 1.6 tonnes for standard 20mm gravel; decorative gravels run nearer 1.5 tonnes and Type 1 sub-base 2.2 tonnes per m³.
How do I convert m3 to tonnes?
Multiply the volume by the material's density in t/m³ — the converter does it for any material in the density table.
How much does 0.5 m3 of gravel weigh?
Around 0.8 tonnes for standard gravel — one 850kg bulk bag is a close match.
How many tonnes is 5 m³ of gravel?
Multiply volume by density: 5 × 1.6 = 8 tonnes of standard gravel before any ordering allowance. The converter above does this for any volume and material.
References and source notes
- Conversion densities from the aggregate planning density table on this page.