How much gravel do I need for my driveway?

Multiply the driveway's length by its width to get the area, then multiply by the depth you want (commonly 10-15 cm/4-6 in for a surface layer over a compacted sub-base). That gives you the volume; this calculator then converts that volume to a weight in tonnes/tons and an estimated cost using your chosen gravel type's density, plus a waste allowance for compaction.

How many tonnes (or tons) are in a cubic metre (or cubic yard) of gravel?

It depends on the gravel type, but a widely used rule of thumb is roughly 1.4-1.5 tonnes per cubic metre of general-purpose gravel (around 1.5-1.65 US tons per cubic yard). Denser materials like pit-run gravel or a gravel/sand mix run higher, around 1.9 tonnes per cubic metre; lighter pea gravel sits a little below the general-purpose figure. Use this calculator's material dropdown to get an exact figure for your gravel type rather than relying on the rule of thumb alone.

How many bags of gravel do I need?

Divide the total weight needed by the bag size — most decorative gravel is sold in 25 kg (or 50 lb) bags. This calculator shows the bag count automatically alongside the bulk weight and volume, so you can compare buying bagged gravel from a hardware store against ordering a bulk load from an aggregate supplier for larger jobs.

What depth of gravel should I use?

It depends on the application: about 5 cm (2 in) for a decorative path topping over landscape fabric, 7.5-10 cm (3-4 in) for a light-use garden path or patio base, and 15-20 cm (6-8 in) of compacted sub-base for a driveway that will carry vehicle weight. Heavier or longer driveways, and areas with soft or clay-heavy soil, often need a deeper sub-base.

Should I add extra gravel for waste or compaction?

Yes — loose gravel settles noticeably once it's spread and compacted, and any real-world job has some spillage and off-cuts at the edges of an irregular area. A 10% allowance is standard for most compacted sub-base work (this calculator applies it by default, adjustable up to 25%), which is exactly the allowance Omni's own gravel calculator omits entirely.

What's the difference between road base and blue metal?

Road base is a compactable mix of crushed rock and fines, purpose-built for driveways and sub-base work because it locks together and drains reasonably well. Blue metal is a cleaner, more uniform crushed basalt aggregate used mainly for concrete mixing and drainage rather than as a walking or driving surface base. Choose the crushed granite or generic gravel option in this calculator as the closest density match for road base, and check your supplier's exact density for blue metal if that's what you're ordering.

How much scoria do I need for garden drainage?

For garden drainage or a decorative scoria bed, a depth of 5-7.5 cm is typical over landscape fabric. Enter your bed's area and that depth into this calculator with a lower waste allowance (scoria used decoratively generally isn't compacted), and it will give you the volume, weight in tonnes and bag count if you're buying from a hardware store rather than ordering in bulk.

Gravel Calculator | Road Base, Blue Metal & Crusher Dust Volume, Weight & Cost

How much gravel do you need?

Ordering gravel by guesswork almost always ends one of two ways: a second delivery charge because you came up short, or a pile of leftover stone taking up space in the driveway. This gravel calculator works out the volume, weight and cost for your project from three numbers you already know — the length and width of the area, and how deep you want the gravel bed — so you can order the right amount the first time.

It covers the jobs gravel actually gets used for: driveways, footpaths and garden paths, patio and shed sub-bases, drainage trenches, and decorative landscaping beds. Pick a gravel type from the dropdown — pea gravel, crushed granite, limestone chip, pit-run or a gravel/sand mix — and the calculator applies that material's bulk density automatically, so the weight and cost figures reflect what you're actually buying, not a generic average.

Unlike a plain length x width x depth sum, this tool also adds a waste and compaction allowance. Loose gravel settles as it's spread and compacted, and every load has some spillage and off-cuts at the edges of an irregular area, so ordering exactly the calculated volume routinely leaves a job under-supplied. The default 10% allowance (adjustable up to 25%) covers that gap without you needing to pad the numbers yourself.

The result comes back as volume (m³ or cubic yards), total weight in tonnes or tons, an estimated cost based on your local price per tonne, and — for smaller decorative jobs — the number of standard 25 kg bags you'd need to buy instead of ordering bulk.

How to use the gravel calculator

Enter the length and width of the area you're covering — a driveway, path, patio base or garden bed.
Enter the depth of gravel you want. Typical depths: 5 cm (2 in) for a decorative path topping, 7.5–10 cm (3–4 in) for a driveway surface layer, and 15–20 cm (6–8 in) for a compacted driveway sub-base.
Choose a gravel type from the material dropdown — pea gravel, crushed granite, limestone chip, pit-run gravel, gravel/sand mix, or a generic "regular gravel" default — or enter a custom density if your supplier quotes one.
Adjust the waste/compaction allowance if needed. The 10% default suits most compacted sub-base jobs; loose decorative gravel that won't be compacted can often use a lower figure, while an irregularly shaped area may need more.
Read off the volume, weight, bag count and estimated cost. Change any input and the results update immediately, so you can compare a couple of depths or gravel types before you order.

The gravel calculation, step by step

The volume of gravel needed is simply the area you're covering multiplied by the depth of the layer: Volume = Length x Width x Depth. Keep the units consistent — if length and width are in metres and depth is in centimetres, convert the depth to metres (divide by 100) before multiplying, or let the calculator's unit switcher handle the conversion for you.

Gravel is bought and delivered by weight, not volume, so the next step converts volume to weight using the material's bulk density: Weight = Volume x Density. Bulk density (how much a cubic metre of the loose material weighs, including the air gaps between stones) varies by gravel type — see the reference table below — so the same volume of pea gravel and pit-run gravel will not weigh the same.

Finally, add the waste/compaction allowance to the volume before converting to weight, since real-world jobs need more material than the bare geometric calculation: Order quantity = Volume x (1 + waste%). Cost is then the ordered weight multiplied by your supplier's price per tonne (or per bag, for small quantities).

Worked example: a driveway measuring 6 m long x 3 m wide, with a 10 cm (0.1 m) compacted sub-base of regular gravel (density 1,680 kg/m³) and a 10% waste allowance. Volume = 6 x 3 x 0.1 = 1.8 m³. With 10% waste: 1.8 x 1.1 = 1.98 m³. Weight = 1.98 x 1,680 = 3,326 kg, or about 3.33 tonnes. At a typical price of $45/tonne that's roughly $150 delivered, before any supplier minimum-load or delivery surcharge.

Gravel bulk density by type

Pea gravel (small, rounded, washed): approximately 1,680–1,700 kg/m³ (105 lb/ft³) — the industry-standard figure widely quoted by aggregate suppliers for small rounded gravel.
Crushed granite (angular, 3/4 in / 20 mm typical): approximately 1,600–1,700 kg/m³, per Martin Marietta and Vulcan Materials aggregate product data sheets.
Crushed limestone chip: approximately 1,500–1,600 kg/m³ (the low-to-mid end of the 1.55–1.75 t/m³ crushed-limestone range published in quarry spec sheets).
Pit-run / bank-run gravel (unwashed, natural mix with fines): approximately 1,900 kg/m³ — denser than clean graded gravel because the fines fill the gaps between larger stones.
Gravel + sand mix: approximately 1,900–1,950 kg/m³ (around 120 lb/ft³) — sand packs into the voids and raises the bulk density above clean gravel alone.
A widely used rule of thumb: roughly 1.4–1.5 tonnes (1.5–1.65 tons) of gravel per cubic metre for general "regular" gravel, or about 1 US ton per 0.7 cubic yards.

Australian aggregate names: road base, blue metal and crusher dust

Australian landscape and building merchants use distinct trade names rather than generic "gravel": "Road Base" is a compactable blend of roughly 20mm crushed rock and decomposed-granite fines used for driveways and footings prep. "Blue Metal" is a uniform crushed basalt/bluestone aggregate, the standard coarse aggregate for concrete mixing and drainage. "Crusher Dust" is fine crushed-rock fines used for paver bedding and compaction, and "Scoria" is a reddish volcanic gravel used for drainage and garden landscaping. Washed river sand and bricklayer's sand are the standard fine-aggregate names.

Pro tips and common mistakes

At a typical Australian price of around A$55 per tonne, a driveway sub-base needing roughly 3.3 tonnes of road base (a 6 m x 3 m area at 10 cm compacted depth, with a 10% waste allowance) would cost approximately A$183 in material, before delivery.

Always allow for compaction. Loose gravel dumped and spread thins out once it's rolled or walked down, especially on a sub-base layer — a 10-15% allowance is standard trade practice for compacted driveway and path bases.
Match the depth to the job, not a single default. A decorative topping over landscape fabric needs only 5 cm; a driveway that will carry vehicle weight needs a properly compacted sub-base of 15-20 cm plus a surface layer, and heavier commercial or long-driveway applications sometimes need more.
Don't skip the sub-base for driveways. A thin layer of decorative gravel laid straight onto soil will rut and disappear into the ground within a season — a compacted crushed-stone sub-base underneath is what actually carries vehicle loads.
Order by weight, not by "looks about right." Suppliers price and deliver aggregate by the tonne; using this calculator's weight output (rather than eyeballing a pile size) is the only reliable way to match your order to your supplier's pricing.
A common mistake: forgetting that "depth" means the compacted finished depth, not the depth of loose material before it's rolled down — loose gravel can occupy noticeably more volume than the same material once compacted.
Round up to the nearest bulk-bag or truckload size your supplier offers — ordering an odd, non-round quantity often costs more per tonne than rounding up slightly to the next standard load size.