Gravel Calculator m3: Volume & Weight

This gravel calculator works out the volume of gravel you need in cubic metres (m³) and its estimated weight in tonnes, based on the length, width, and depth of the area you want to cover. You enter the dimensions in metres or centimetres, choose a gravel type, and the calculator returns the cubic metres and tonnes required. The weight estimate uses typical bulk densities for common gravel types, which you can adjust if you know the exact density of your material.

Formula

The core formula is simple: Volume (m³) = Length (m) × Width (m) × Depth (m). Since you usually measure depth in centimetres, convert it to metres by dividing by 100. The weight is then Weight (tonnes) = Volume (m³) × Density (kg/m³) / 1000.

Variables:

• Length – the longest side of the area, in metres (m).
• Width – the shorter side, in metres (m).
• Depth – how thick the gravel layer will be, in centimetres (cm).
• Density – the mass per cubic metre of the specific gravel, in kilograms per cubic metre (kg/m³).

The result is the volume in cubic metres, and the weight in tonnes (metric tons). One tonne equals 1,000 kilograms.

Worked Example

Using the default values: length = 5 m, width = 3 m, depth = 10 cm, and gravel type = pea gravel (density 1680 kg/m³).

1. Convert depth to metres: 10 cm ÷ 100 = 0.1 m.
2. Calculate volume: 5 × 3 × 0.1 = 1.5 m³.
3. Calculate weight: 1.5 × 1680 = 2520 kg.
4. Convert to tonnes: 2520 ÷ 1000 = 2.52 tonnes.

The calculator shows 1.50 m³ and 2.52 tonnes for these inputs.

Why Gravel Is Sold by the Tonne, Not the Cubic Metre

Gravel is a bulk material, and suppliers typically sell it by weight (tonnes) rather than by volume (cubic metres). The reason is that gravel compacts and settles differently depending on its size, shape, and moisture content. A cubic metre of dry pea gravel weighs less than a cubic metre of wet crushed stone. By selling by weight, suppliers ensure you get the same mass of material regardless of how it settles during transport.

However, you plan your project in volume – you need to fill a space of known dimensions. That is why the calculator first finds the volume, then converts to weight using a standard density. The density values used (1600–1700 kg/m³) are typical for loose gravel; compacted gravel can be 10–20% heavier.

How to Choose the Right Gravel Type

Your choice of gravel affects both the look and the weight calculation. Here are common types and their typical densities:

• Pea gravel – small, rounded stones, often used for paths and play areas. Density ~1680 kg/m³.
• Crushed stone – angular, jagged pieces, good for driveways and base layers. Density ~1600 kg/m³.
• Bank gravel – a mix of sand and gravel, often used as a base. Density ~1700 kg/m³.
• Limestone – a common crushed rock, available in various sizes. Density ~1650 kg/m³.

If you know the exact density of your gravel (ask your supplier or check the product spec), you can adjust the calculation manually. For most projects, the difference between 1600 and 1700 kg/m³ is small – about 6% – so the estimate is usually sufficient.

Common Mistakes When Calculating Gravel

Several errors can lead to ordering too much or too little gravel:

• Mixing units – measure everything in metres, or convert centimetres to metres first. A depth of 10 cm is 0.1 m, not 10 m.
• Forgetting compaction – gravel compacts by about 10–20% when rolled. If you need a final depth of 10 cm, you may need to order 10–15% more to account for settling.
• Ignoring the sub-base – for driveways, you often need a deeper layer of coarse gravel underneath the decorative top layer. The calculator works for a single layer; for multiple layers, calculate each separately.
• Assuming 1 m³ = 1 tonne – this is only true for water. Gravel is about 1.6–1.7 times denser, so 1 m³ of gravel weighs roughly 1.6–1.7 tonnes.

How to Measure an Irregular Area

Most gravel areas are not perfect rectangles. For L-shaped or irregular spaces, break the area into rectangles, calculate each one, and add the volumes together. For circular areas, use the formula π × radius² × depth (π ≈ 3.1416). For a triangular area, use 0.5 × base × height × depth.

If your area has a slope, measure the depth at the shallowest and deepest points and use the average. This gives a more accurate volume than measuring at one spot.

Ordering Gravel: What to Tell the Supplier

When you call a supplier, you will need to provide either the volume in cubic metres or the weight in tonnes. Most suppliers will ask for the area dimensions and the desired depth, then calculate the volume themselves. But knowing your own estimate helps you avoid over-ordering.

Keep in mind that gravel is often sold in bulk bags (typically about 0.5–1 m³) or by the tonne for loose delivery. A typical bulk bag holds around 0.5 m³, so for 1.5 m³ you would need three bags. For loose delivery, the supplier will ask for the tonnage, which the calculator provides.

Frequently Asked Questions

How many tonnes is 1 cubic metre of gravel?

It depends on the gravel type, but a typical range is 1.6 to 1.7 tonnes per cubic metre. Pea gravel is about 1.68 tonnes/m³, crushed stone about 1.60 tonnes/m³. This is based on loose, dry material; wet or compacted gravel can be heavier.

What depth of gravel do I need for a driveway?

For a residential driveway, a common recommendation is 10–15 cm of compacted gravel. This usually means a base layer of 10 cm of coarse crushed stone, then a top layer of 5 cm of finer gravel. For a path or patio, 5–8 cm is usually enough.

How do I calculate gravel for a circular area?

Measure the radius (half the diameter) in metres, square it, multiply by π (3.1416), then multiply by the depth in metres. For example, a circular patio with a 3 m radius and 10 cm depth: 3.1416 × 3 × 3 × 0.1 = 2.83 m³.

Should I order extra gravel for compaction?

Yes, it is wise to order about 10–15% more than the calculated volume. Gravel settles and compacts when rolled, so the final depth will be less than the loose depth. This buffer also covers measurement errors and spillage.

Is the weight estimate accurate for all gravel types?

The estimate is accurate for typical loose gravel, but actual density varies with moisture, stone size, and compaction. If you need a precise weight, ask your supplier for the exact density of the product you are buying, then multiply the volume by that density.

Can I use this calculator for sand or soil?

Yes, the volume calculation is the same for any bulk material. However, the weight estimate will be off because sand and soil have different densities – sand is about 1600 kg/m³, and topsoil about 1100 kg/m³. For those, use a density-specific calculator or adjust the weight manually.

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in length | Length | m | 5 | 0
in width | Width | m | 3 | 0
in depth | Depth | cm | 10 | 0
sel type | Gravel type | Pea gravel=1680, Crushed stone=1600, Bank gravel=1700, Limestone=1650
out volume | Volume | m³ | length * width * (depth / 100) | 2
out weight | Estimated weight | tonnes | volume * type / 1000 | 2