Gravel Calculator

This free gravel calculator estimates aggregate volume, weight and whole-bag counts for projects including driveways, garden paths, borders and drainage. Enter your dimensions in metres or feet, set the depth in centimetres or inches, choose your gravel type, and get an instant estimate in cubic metres, tonnes, bulk bags and 25kg bags.

The calculator uses a simple formula (length × width × depth) to find the volume, then multiplies by the density of your chosen gravel type to convert into weight. This matters because gravel in the UK is sold by weight (tonnes or kilograms), not by volume. Different types of gravel have different densities: the calculator assumes about 2,100 kg/m³ for MOT Type 1, while decorative aggregate is assumed at 1,400 kg/m³. These are category assumptions used by this calculator, not specifications for a chosen product. Before ordering, ask the manufacturer or supplier for the product’s bulk density and packed weight, then use those figures to check the estimated quantity and whole-bag count.

Planning a landscaping project? Our mulch calculator works out bark and wood chip quantities, and the soil calculator handles topsoil and compost for raised beds and borders.

Driveway build-ups vary with vehicle loads, ground and drainage conditions. The table below shows surface-layer calculator examples for common driveway dimensions.

Driveway Gravel Quantities

Driveway Size	Gravel Depth	Volume (m³)	Weight (tonnes)	Buying Price
Single car (3m × 6m)	50mm	0.90	1.35	Get a supplier quote
Double car (5m × 6m)	50mm	1.50	2.25	Get a supplier quote
Long drive (3m × 15m)	50mm	2.25	3.38	Get a supplier quote
Large drive (5m × 10m)	50mm	2.50	3.75	Get a supplier quote

Important: These worked quantities use a selected 50mm surface depth only to demonstrate calculator output. They are not a driveway build-up recommendation. Have a competent driveway contractor or engineer specify the full build-up for the expected vehicle loads, ground and drainage conditions. Then use the specified depths to estimate the separate material quantities and check each chosen product’s bulk density and packed weight.

Choose the driveway surface material from the project specification. Do not rely on stone size or a decorative product name alone; confirm that the exact product is specified for the expected vehicle loads.

Planning Permission for Gravel Driveways

In England, replacing your front garden with an impermeable surface larger than 5 m² requires planning permission under Schedule 2, Part 1, Class F of the Town and Country Planning (General Permitted Development) (England) Order 2015.⁶ The Planning Portal explains this in plain English:⁷ if the surface drains freely to a lawn or border rather than to a drain or the road, no permission is needed. Gravel is a permeable surface by nature, provided it does not compact into an impermeable layer. The DCLG guidance on permeable surfacing of front gardens⁸ sets out the recommended build-up: coarse, open-graded gravel on a permeable sub-base, allowing rainwater to drain freely into the ground beneath. Scotland, Wales and Northern Ireland set their own permitted-development rules, so check with your local planning authority before surfacing a front garden there.

Gravel is sold by stone size in millimetres, following nominal size conventions set out in the aggregate grading standard¹ for unbound materials. Nominal size alone does not establish suitability. Choose the stone size and material from the project requirements and chosen manufacturer or supplier specification.

Nominal Size	Calculator Density Assumption (per m³)
6mm	1,600 kg
10mm	1,600 kg
14mm	1,600 kg
20mm	1,500 kg
40mm	1,600 kg
Slate (20–40mm)	1,500 kg

Project check: Choose the stone size, depth and any edging from the project requirements and chosen supplier’s specification. Check the intended use, ground, drainage, access and maintenance needs before ordering.

Gravel products differ by stone shape, nominal size and product specification. Compare the intended use, site conditions, access and maintenance needs with the project requirements and chosen manufacturer or supplier specification before selecting a material.

10mm Pea Gravel

Pea gravel is one of the decorative aggregate options sold for UK gardens. The small, rounded stones are commonly offered for seating zones and as a decorative top-dressing for plant borders. Product suitability varies with the surface, slope and installation. Check the project requirements and the chosen manufacturer or supplier specification before selecting pea gravel or an angular aggregate for a path. The calculator assumes a density of around 1,600 kg/m³ for this type, so a cubic metre weighs approximately 1.6 tonnes.

20mm Gravel and Shingle

For garden paths and general landscaping, choose the gravel size from the project requirements and the chosen manufacturer or supplier specification. Check the surface, slope, access and maintenance needs before ordering. The calculator uses approximately 1,500 kg per cubic metre for 20mm gravel and shingle. For driveway use, choose the material and full build-up from the project specification.

Decorative Aggregate

This covers everything from golden flint to plum slate, rainbow stone and white marble chips. Decorative aggregates are lighter (the calculator uses around 1,400 kg/m³) and are chosen primarily for appearance rather than structural performance. I used Cotswold Gold aggregate for the borders around my front garden and it has held its colour well after two years, though I did top it up slightly after the first winter. Choose the material and depth from the project requirements and the chosen supplier’s specification.

MOT Type 1

MOT Type 1 is not really a garden gravel: it is a crushed limestone sub-base material used underneath driveways, patios and shed bases. It compacts down hard when vibrated with a plate compactor, creating a stable foundation.¹ The calculator assumes about 2,100 kg/m³ for this material, making it significantly heavier than decorative gravel. For a driveway, have a competent driveway contractor or engineer specify the full build-up for the expected vehicle loads, ground and drainage conditions. Enter the specified sub-base depth in the sub-base calculator.

Slate Chippings

Welsh slate chippings in 20mm or 40mm sizes give a contemporary, modern look to garden borders and paths. The dark blue-grey colour contrasts beautifully with green planting and light-coloured walls. In my own raised beds, some 40mm slate has shown no visible deterioration after four years. That is my personal experience in one garden, not a product lifespan claim. Check the chosen supplier’s product and maintenance specifications for the project. The calculator uses a density similar to standard gravel at around 1,500 kg/m³.

Gravel Type	Calculator Density Assumption (kg/m³)
10mm Pea Gravel	1,600
20mm Gravel/Shingle	1,500
Decorative Aggregate	1,400
MOT Type 1	2,100
Slate Chippings	1,500

I have laid gravel in three separate areas in my own garden. The area where I skimped on preparation became weedy and uneven, and I ended up redoing it. That is my personal experience. Follow the project specification for preparation and installation.

Step 1: Mark Out and Excavate

Use string lines and pegs to mark your area. For a decorative border, set the excavation depth and preparation to match the project requirements, site conditions and chosen manufacturer or supplier specification. For a driveway, do not use a generic excavation depth. Have a competent driveway contractor or engineer specify the excavation and full build-up for the expected vehicle loads, ground and drainage conditions.

Step 2: Decide on Edging

Choose whether edging is required, together with its type and installation method, from the project requirements and chosen supplier’s specification. For driveways, have a competent driveway contractor or engineer specify the edging and full build-up for the expected vehicle loads, ground and drainage conditions.

Step 3: Lay Weed Membrane

If the project calls for a membrane, follow the project and chosen manufacturer’s specification for the product type, placement, overlaps and fixings. For a driveway, have the full build-up specified for the expected vehicle loads, ground and drainage conditions.

Step 4: Compact the Sub-Base (Driveways Only)

For driveways and areas with vehicle traffic, follow the project specification for the sub-base material, layer depths, compaction method and drainage. Have a competent driveway contractor or engineer prepare that specification for the expected vehicle loads, ground and drainage conditions.

Step 5: Spread and Level the Gravel

Tip your gravel onto the membrane (or sub-base for driveways) and spread it with a landscaping rake. Work in sections, checking depth with a ruler or offcut of timber marked at the right depth. For paths and borders, use the depth in the project requirements and chosen supplier’s specification. For driveways, use the surface depth in the project specification. Rake it level and use a spirit level on a straight edge to check for any dips.

Step 6: Consider Gravel Grid Panels

For driveways and parking areas, follow the project specification before choosing any gravel grid system. Ask the grid manufacturer and driveway contractor to confirm the product, full build-up and installation method are suitable for the expected vehicle loads, ground and drainage conditions.

Use the calculator to estimate the weight and whole-bag count. Then ask suppliers for written quotes stating the material specification, packed weight or loose tonnage, delivery charge and total price. Compare like for like rather than relying on a headline bag or tonne price.

This calculator uses 850kg per bulk bag.¹¹ Check the packed weight of the product being quoted because supplier bags vary. For a driveway, obtain the full build-up from the project specification before requesting a combined materials-and-delivery quote.

I see the same mistakes repeated on gardening forums every spring. Here are the ones that cost the most time and money to fix.

Skipping the Weed Membrane

On my first gravel border, I skipped the membrane and later spent an entire summer pulling out couch grass and dandelions. That was my own experience. Whether a membrane is needed depends on the project, so follow the project specification and choose a product that matches it.

Using Unspecified Edging

Do not assume that every gravel area needs the same edging. Use the project requirements and chosen supplier’s specification to decide whether edging is required and to choose its type and installation method.

Laying Gravel Directly on Clay Soil

Clay conditions vary by site. For a driveway on clay, have a competent driveway contractor or engineer specify the excavation, geotextile, drainage and full build-up after assessing the ground and expected vehicle loads.

Ordering Too Little

Use the calculator for the measured area and specified depth. If the ground is irregular or the chosen product requires an allowance, use the product guidance or ask the supplier or contractor how the order quantity should be adjusted.

Choosing a Surface Without a Specification

Do not choose a driveway aggregate by stone size or appearance alone. Have the surface material and full build-up specified for the expected vehicle loads, ground and drainage conditions, then order that exact material.

Maintenance needs vary with the chosen product, full build-up, traffic, weather and site conditions. Use the project requirements and chosen supplier’s maintenance instructions to decide what to inspect, which maintenance tasks are suitable and when they are needed.

Raking and Levelling

Inspect the surface for dips, displaced gravel and tyre tracks as required by the project specification. If raking is part of the maintenance instructions for the chosen product and build-up, follow those instructions and rake only when the inspection shows it is needed.

Weed Control

Inspect the surface for weeds as required by the project specification. Follow the chosen surface and weed-control product instructions, and confirm that any treatment is suitable for the aggregate before use.

Topping Up

Inspection and maintenance needs depend on the product, build-up, traffic, weather and project specification. Follow the chosen supplier’s maintenance instructions and inspect the surface, edging and drainage. Repair or top up only when inspection shows it is needed.

Leaf and Debris Removal

Inspect for leaves and other debris as required by the project specification. Follow the chosen supplier’s maintenance instructions for the product, full build-up and site conditions when deciding what to remove, which tools and settings are suitable, and when to carry out the work.

Choose each gravel depth from the project requirements and chosen supplier’s specification. For a driveway, have the full build-up specified for the expected vehicle loads, ground and drainage conditions.

Project	Depth (cm)	Depth (inches)	Notes
Driveway (over sub-base)	Use project specification	Use project specification	Have the full build-up specified for the site
Garden path	Use the project requirements and chosen supplier’s specification		Choose for the intended use, site and product
Patio border / edging	Use the project requirements and chosen supplier’s specification		Follow the chosen product’s installation specification
Where impact-attenuating surfacing is required beneath play equipment	Use the tested surface specification		Use a surface tested to BS EN 1177 whose Critical Fall Height is at least the equipment’s maximum free height of fall. Install it across the required impact area.
Drainage / French drain	Use the project requirements and chosen supplier’s specification		Have the drainage design and chosen material specified for the site
Decorative border	Use the project requirements and chosen supplier’s specification		Check the intended use, ground, drainage and maintenance needs
Japanese / Zen garden	Use the project requirements and chosen supplier’s specification		Choose the material and installation from the project and product specifications

The table shows the theoretical litres per square metre at example depth inputs, along with estimated weights using the calculator’s stated 1,500 kg/m³ density assumption. The rows are quantity references, not depth or suitability recommendations. Choose the depth from the project requirements and chosen supplier’s specification, then verify the chosen product’s bulk density before ordering.

Depth (cm)	Litres per m²	kg per m² (20mm gravel)
2	20	30
3	30	45
4	40	60
5	50	75
7	70	105
10	100	150
15	150	225
20	200	300
Where impact-attenuating surfacing is required beneath play equipment: Use a surface tested to BS EN 1177 whose Critical Fall Height is at least the equipment’s maximum free height of fall. Install it across the required impact area. This table does not specify a play-surface depth.

Worked calculator example: Enter a 4m × 2.5m garden path at a selected 5cm depth to show the arithmetic, not to specify a path depth. That is 10 m² × 50 litres = 500 litres of gravel, which weighs 10 m² × 75 kg = 750 kg. Under these assumptions, the whole-bag estimate is one 850kg bulk bag or 30 bags of 25kg. Use our gravel calculator above to estimate your project quantity.

At the calculator’s selected 5cm depth, its MOT Type 1 assumption gives 105 kg per square metre and its decorative aggregate assumption gives 70 kg per square metre. These are category assumptions, not a product specification. Check the chosen product’s bulk density and packed weight with the manufacturer or supplier before ordering.

Compare all suitable buying methods for the calculator estimate. Check the packed weight of bags, the loose tonnage, the delivery method, vehicle access requirements and the delivered total. Compare the delivered total only when the quoted quantity and delivery terms match.

Tell the supplier where the load can be placed and ask what access their vehicle requires. For a driveway, obtain the full build-up from the project specification and request one quote covering the specified surface material, sub-base material and delivery.

Choose the material specification for the job before comparing prices. Ask each supplier to quote the same quantity, grading, packed weight or loose tonnage, delivery terms and total price. For a driveway, use the project specification for both the sub-base and surface material.

GardenCalc does not publish fixed gravel prices here because it does not have dated evidence for every material, package size and delivery charge. Get written like-for-like quotes for the estimated quantity.