About

Ordering construction aggregates by volume often leads to shortages or costly surpluses. Quarries sell by weight (tonnes), but project estimates are calculated in volume (cubic meters). This discrepancy requires precise density conversion factors that vary significantly based on the rock type and fraction size (granulometry). A cubic meter of 0-5mm granite dust weighs significantly more than 40-70mm coarse ballast due to the void ratio (air gaps) between stones.

This tool serves as a procurement assistant for site managers and quantity surveyors. It utilizes a specific database of bulk densities for standard fractions used in road base, drainage, and concrete production. Correct estimation prevents project delays caused by material shortages and reduces waste from over-ordering.

Formulas

The conversion relies on the bulk density formula:

m = V × ρ

Where:

m is the Mass (Total Weight in kg).
V is the Volume (m³).
ρ is the Bulk Density (kg/m³).

To convert to metric tonnes:

Weight_(t) = m_(kg)1000

Reference Data

Material Type	Fraction (mm)	Density (kg/m³)	Density (t/m³)	Typical Use
Granite Screenings	0-5 mm	1450	1.45	Paving blocks, bedding
Crushed Gravel	5-20 mm	1350	1.35	Concrete, drainage
Coarse Gravel	20-40 mm	1350	1.35	Road sub-base, heavy drainage
Large Ballast	40-70 mm	1320	1.32	Railway ballast, soakaways
Construction Rubble	Mixed	1500	1.50	Temporary roads, fill
Limestone Chips	10-20 mm	1380	1.38	Driveways, paths
Basalt Aggregate	5-20 mm	1600	1.60	High-strength concrete
Sandstone	Mixed	1300	1.30	General fill

Frequently Asked Questions

The weight differs due to the "void ratio". Smaller particles (0-5mm) pack together tightly, leaving little air space, which results in a higher density. Larger stones (40-70mm) have large air gaps between them, resulting in a lower bulk density per cubic meter, even if the rock itself is heavy.

Solid density refers to the rock material itself with no air gaps. Bulk density accounts for the air voids found in a pile of crushed stone. For ordering materials, you must always use bulk density.

Yes. Wet sand or gravel can weigh 15-20% more than dry material. This calculator uses standard dry bulk density values. If ordering wet material during winter or rain, add a safety margin to your weight calculation.

Typically, a "MOT Type 1" or equivalent sub-base (often a mix of 0-40mm) is used because the blend of dust and stones compacts very hard. Clean 20mm gravel is used for the top drainage layer.