Cubic metres to tonnes calculator
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| Convert | m³ to tonnes |
| Material | MOT Type 1 sub-base |
| Volume | 3 m³ |
| Density | 2.1 t/m³ |
| Bulk bag size | 0.85 t |
3.00 m³ ≈ 6.30 t
| Result | Value |
|---|---|
| Weight | 6.3 t |
| Volume | 3 m³ |
| Bulk bags | 8 |
| Range for this material | 6 to 6.6 t (density 2 to 2.2 t/m³) |
Show the working
- Weight: 3 m³ × 2.1 t/m³ = 6.3 t
- Bulk bags: 6.3 t ÷ 0.85 t, rounded up = 8
How it works
- Tonnes = m³ × density (t/m³)
- m³ = tonnes ÷ density
- Bulk bags = tonnes ÷ bulk bag size, rounded up
Density varies with moisture and grading: your supplier's figure beats ours.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Density: MOT Type 1 sub-base | 2.1 t/m3 Sources range 2–2.2 t/m3 | Typical value Not yet checked against the source | agg.directory calculator (worked 4.2 t example) (checked 19 October 2026) Compacted. Supplier's figure takes precedence. |
| Density: Recycled Type 1 | 1.9 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) Compacted. |
| Density: All-in ballast | 1.8 t/m3 Sources range 1.7–1.9 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) |
| Density: Sharp sand | 1.6 t/m3 Sources range 1.6–1.7 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) Damp sand bulks; order by weight. |
| Density: Building (soft) sand | 1.5 t/m3 Sources range 1.4–1.6 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) |
| Density: Gravel | 1.6 t/m3 Sources range 1.6–1.75 t/m3 | Typical value Not yet checked against the source | agg.directory calculator; aggregatecalculator.co.uk density table (checked 19 October 2026) Gravel and pea shingle. Sources differ, so the range is shown. |
| Density: Decorative aggregate | 1.5 t/m3 Sources range 1.3–1.7 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) Decorative stone varies with stone type. |
| Density: Topsoil | 1.4 t/m3 Sources range 1.4–1.5 t/m3 | Typical value Not yet checked against the source | rospower.co.uk tonnage calculator (exact page to confirm) (checked 19 October 2026) |
| Density: Concrete | 2.4 t/m3 | Typical value Not yet checked against the source | tradecalculator.co.uk m³-to-tonnes converter (checked 19 October 2026) Supplier's figure takes precedence. |
| Bulk bag size | 0.85 t | Common UK size Not yet checked against the source | builder.tools bulk bag figure (checked 19 October 2026) Varies by merchant; check yours. |