Start with the cross-section, not a rule of thumb
Every road is a stack of layers, and each layer needs a different material. A typical flexible pavement runs, from the bottom up, a Granular Sub-Base (GSB), a base of Wet Mix Macadam (WMM) or Water Bound Macadam (WBM), and then a bituminous surface that carries its own coarse aggregate. The quantity of each layer depends entirely on three numbers you control: the finished width of that layer, its compacted thickness, and the length you are building. There is no honest single "tonnes per km" figure, because a 3.5 m village road and a 7 m two-lane road with shoulders are completely different jobs.
The basic formula
For any single layer, the compacted volume is simply:
- Compacted volume (m³) = length (m) × width (m) × compacted thickness (m)
- Loose volume to order = compacted volume × a compaction allowance (granular layers lose roughly 20–30% of loose volume when rolled, so many engineers multiply by about 1.2–1.3)
- Tonnage = loose volume × the bulk density of the material
Compacted crushed-stone granular material commonly sits around 1.7–2.0 tonnes per cubic metre depending on gradation and moisture; treat this as an approximate planning band and confirm the field density with your own site engineer, because it varies with the source rock and how well it is compacted.
Which material goes in which layer
| Layer | Typical material | Notes |
|---|---|---|
| Sub-base | GSB (MoRTH 401) | Graded granular blend spread over the prepared subgrade. |
| Base | WMM, or WBM | WMM uses graded aggregate mixed with water; WBM is laid in courses with screenings. |
| Surface aggregate | 20mm and 12mm blue metal | Coarse aggregate for bituminous mixes and premix carpet. |
| Bedding / haunching | Crusher dust | Used for kerb bedding, pipe surround and blinding. |
A worked, illustrative example
Suppose you are estimating one kilometre of a single carriageway and, purely for illustration, you assume a 7 m formation with a 200 mm GSB layer. The compacted GSB volume would be 1000 × 7 × 0.20 = 1400 m³. Applying a loose-volume allowance and a density in the band above gives an order in the region of a few thousand tonnes for that one layer alone. The point of the example is the arithmetic, not the number: swap in your real width and thickness from the approved drawings and the figure changes completely. Always work from your own cross-section and BOQ.
Where M-Sand fits on a road job
Roads are mostly coarse aggregate, but M-Sand still appears wherever there is concrete — kerbs, drains, culverts, catch pits, retaining structures and rigid pavement panels. For those elements you estimate sand the same way you would for any concrete: from the concrete volume and the mix design. Plaster on associated structures uses P-Sand.
Practical ordering tips
- Order by compacted layer, not by the whole road. It keeps your stockpiles matched to the sequence of work and reduces double handling.
- Add a wastage margin. Spillage, edge losses and grade corrections mean the delivered quantity is always a little more than the theoretical volume.
- Confirm gradation against the spec. GSB and WMM are defined by their grading envelope, so ask that each load meets the relevant MoRTH grading — see our grading explainer for how this works.
- Sequence deliveries in tipper loads. Material moves in full 10-wheeler tippers, so round your layer quantities to whole loads when you plan site access and rolling.
When you have your width, thicknesses and lengths ready, share them with us and we will help you convert them into loads. For current rates, see the pricing page or request a quote.
Quick answers
Is there a fixed tonnage of aggregate per km of road?
No. The quantity depends on the road's width, each layer's compacted thickness and the material density. A narrow village road and a wide two-lane road differ greatly, so always calculate from your own approved cross-section.
How do I convert compacted volume to tonnes to order?
Multiply the compacted volume by a compaction allowance to get loose volume, then by the material's bulk density (approximately 1.7 to 2.0 tonnes per cubic metre for compacted crushed granular material). Confirm density with your site engineer.
Which materials does a road actually use?
Generally GSB for the sub-base, WMM or WBM for the base, and 20mm and 12mm blue metal for the bituminous surface. Concrete elements like kerbs and drains use M-Sand, and crusher dust is used for bedding and blinding.
Where does M-Sand fit on a road project?
Wherever there is concrete such as kerbs, drains, culverts and rigid pavement panels. Estimate it from the concrete volume and mix design, and use P-Sand for plaster on associated structures.