Crushed Stone Calculator

Area dimensions
Layer thickness
Fraction and origin

INPUT DATA

m
m
cm
%
kg/m³

RESULTS

m²
m³
t
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About Crushed Stone Calculation

The results are approximate. Before use, verify the calculations against the applicable standards and consult a specialist. The developer is not responsible for the consequences of use without project verification.

The crushed stone calculator determines material volume in m³ and mass in tonnes from the area, layer thickness, aggregate size fraction, origin and moisture. It also calculates the loose volume required when a compaction allowance is applied.

These calculations are useful for crushed stone sub-bases, garden paths, paved areas, drainage layers and other construction applications using crushed stone. Material quantities are calculated from geometric dimensions and loose bulk density, with allowances for placement conditions.

Guidelines and recommendations

Calculating area and layer volume

Area. For a rectangular surface, multiply the length by the width, both in metres. For a circular surface, calculate the area from its diameter. If the area is already known, use it directly.

S = L × W

S = π × D2 / 4

Here S is the area in m², L the length in m, W the width in m and D the circle diameter in m. The value of π is approximately 3.14159.

Finished layer volume. Multiply the area by the required layer thickness. As thickness is entered in centimetres, divide it by 100 to convert it to metres.

V1 = S × h / 100

Here V1 is the finished layer volume in m³, S the area in m² and h the thickness in cm. For example, an area of 50 m² and a thickness of 5 cm give a volume of 2.5 m³.

Compaction allowance

Loose crushed stone volume. During compaction, the material occupies less space because voids between particles decrease. Therefore, more loose crushed stone may be needed than the geometric volume of the finished layer.

V2 = V1 × (1 + C / 100)

Here V2 is the required loose volume in m³, V1 the finished layer volume in m³ and C the compaction allowance in percent. For example, with a 10% allowance, a finished layer of 2.5 m³ requires 2.75 m³ of loose crushed stone.

Typical allowances. For clean fractions with few fines, approximate values of 5-15% are often used. For mixtures containing fines, such as 0/31.5, 0/45 and 0/63, estimates of 15-30% are common and may sometimes be higher. The actual allowance depends on particle size distribution, initial material condition and the compaction method.

At 0% allowance, the loose volume is taken to equal the finished layer volume. The calculator does not derive the allowance automatically from the fraction. It uses the value entered by the user.

Fraction, origin and loose bulk density

Loose bulk density. This is the mass of 1 m³ of loose crushed stone, including the spaces between its particles. It differs from the density of the solid rock and depends on particle size, particle shape and material composition.

The calculator uses the following initial indicative loose bulk density values:

  • Fractions 4/8, 8/16, 16/32 and 32/63 mm - 1500 kg/m³.
  • Fractions 0/31.5, 0/45 and 0/63 mm - 1650 kg/m³.

Origin adjustment. A fixed value is added to or subtracted from the initial density according to the selected rock type:

  • Granite crushed stone - increase of 50 kg/m³.
  • Limestone crushed stone - decrease of 50 kg/m³.
  • Dolomite crushed stone - decrease of 30 kg/m³.
  • Crushed natural gravel - no adjustment.

For example, the calculated loose bulk density is 1550 kg/m³ for 8/16 mm granite crushed stone and 1450 kg/m³ for limestone crushed stone of the same fraction.

These figures are approximate calculator assumptions, not mandatory properties of these rock types. Actual loose bulk density can differ considerably. For a more accurate calculation, use the supplier's value or one obtained by testing the material. For a custom fraction, enter the density manually.

Calculating mass and accounting for moisture

Crushed stone mass. Multiply the loose volume by the loose bulk density and apply the moisture adjustment. The calculated mass is then converted from kilograms to tonnes.

M = V2 × ρ × K / 1000

Here M is mass in tonnes, V2 the loose volume in m³, ρ the loose bulk density in kg/m³ and K the moisture factor.

Moisture adjustment. The calculator uses three fixed factors:

  • Dry crushed stone - 1.00 (no increase in mass).
  • Damp crushed stone - 1.02 (mass increased by 2%).
  • Wet crushed stone - 1.04 (mass increased by 4%).

This adjustment affects calculated mass only. The geometric layer volume and loose volume remain unchanged. The moisture percentages are simplified assumptions, since actual water content depends on storage conditions, material composition and water absorption.

Calculation example. For an area of 50 m², a thickness of 5 cm, a 10% compaction allowance and dry 8/16 mm granite crushed stone with a loose bulk density of 1550 kg/m³, the results are:

  • Finished layer volume - 2.5 m³.
  • Loose volume allowing for compaction - 2.75 m³.
  • Crushed stone mass - 4.263 t.

Mass is calculated using unrounded intermediate values and displayed to 0.001 t. Volumes of 0.1 m³ or more are rounded to 0.001 m³, while smaller volumes are rounded to 0.0001 m³.

European standards

The following European standards are used for classification, testing and specification of crushed stone and aggregates:

  • EN 13242 - Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction. Specifies requirements for aggregate characteristics.
  • EN 13285 - Unbound mixtures. Specifications for materials mainly used in the construction and maintenance of roads and other trafficked areas.
  • EN 12620 - Aggregates for concrete. Specifies requirements for the properties of aggregates used in concrete.
  • EN 1097-3 - Tests for mechanical and physical properties of aggregates. Part 3: Determination of loose bulk density and voids.

These standards concern material characteristics and testing. The density values, origin adjustments, moisture factors and compaction allowances used here are calculation assumptions, not standardised coefficients specified by these standards.

FAQs

How much crushed stone is needed for 1 m² at a layer thickness of 10 cm?

The geometric layer volume is 0.1 m³ per square metre. With a 10% compaction allowance, 0.11 m³ of loose crushed stone is required. At a loose bulk density of 1500 kg/m³ for dry material, the calculated mass is 165 kg, or 0.165 t.

Why are the finished layer volume and the amount of crushed stone to order different?

During compaction, crushed stone particles pack more closely together and the void volume decreases. The initial amount of loose material may therefore be greater than the finished layer volume. The calculator accounts for this difference through the percentage compaction allowance.

Why can the same volume of crushed stone have a different mass?

Mass depends on loose bulk density, which varies with the fraction, rock type and composition. For example, 1 m³ of dry loose crushed stone has a mass of 1.5 t at 1500 kg/m³, compared with 1.65 t at 1650 kg/m³. Moisture can further increase the mass.

How can I determine the loose bulk density of crushed stone?

The most suitable value is available from the supplier's technical specifications for the specific material. If such data is unavailable, the calculator uses indicative values from 1500 to 1650 kg/m³, with adjustments for origin. These estimates help calculate crushed stone quantities but do not replace the actual properties of the supplied material.

Which compaction allowance should I use for crushed stone?

Typical indicative allowances are 5-15% for clean coarse fractions and 15-30% for mixtures with fines. The choice depends on crushed stone composition, equipment and the required degree of compaction. Where actual consumption data from similar work is available, it is better to determine the allowance from that data.