Aggregate Calculator: How Much Gravel, Hardcore or Type 1 Do You Actually Need?
Standing in a builders' merchant, pointing at a mountain of stone, trying to guess how many bags or tonnes you need is a mug's game. Order too little and you're back in the van on Saturday morning. Order too much and there's half a ton of Type 1 sulking on your driveway until Christmas. The good news: every loose material on this page — gravel, hardcore, Type 1, sand, topsoil, the lot — is worked out with the exact same sum. Learn it once and you'll never over-order again.
This is the pillar guide for the whole aggregate family. Each section tells you what the material's for, the depth to lay it at, and roughly how far a tonne goes — then drops you straight into the right calculator for your actual numbers.
The one rule that covers every aggregate
Here it is, the sum behind all of it:
Volume = length × width × depth. Then multiply that volume by the material's density to get the weight in tonnes.
That's genuinely the whole trick. A patio sub-base, a gravel path, a raised bed of topsoil — same maths, you just swap the depth and the density. Density is simply how heavy a cubic metre of the stuff is: chunky stone is heavy, bark is light, everything else sits in between. You don't need to memorise the numbers — the aggregate calculator holds them for you. But it helps to know roughly where each material lands so a delivery quote doesn't catch you out.
One habit worth keeping: always add about 5–10% for wastage and settlement. Loose stone beds down once it's compacted, and you'll lose a bit to uneven ground. Better a spare barrow-load than a gap.
Gravel & decorative stone
The friendliest material on site — you tip it, you rake it, you're done. Decorative gravel, pea shingle, Cotswold chippings and the like are your go-to for paths, borders and dressing a driveway. Lay it too thin and the ground grins through; too thick and you're wading. The sweet spot for a path or border is around 40–50mm (1.5–2in); for a gravel driveway that takes a car, go closer to 50mm over a proper sub-base.
Gravel is a middleweight — roughly 1.5 to 1.75 tonnes per cubic metre — so as a rough steer, a tonne covers somewhere around 10–14 m² at 50mm deep. Your exact spot will depend on the stone size, so punch your measurements into the gravel calculator and let it do the fiddly bit. For decorative and landscaping stone specifically, the decorative gravel guide and river rock calculator cover the chunkier, prettier end.
MOT Type 1 (the sub-base)
Type 1 is the unsung hero — the crushed limestone or granite that goes under everything solid. Driveways, patios, sheds, block paving: they all sit on a compacted Type 1 sub-base, because without it the pretty top layer sinks and cracks the first winter. It's the boring layer nobody sees and everybody needs.
Lay it at 100–150mm (4–6in) for a driveway that carries a car, less for a footpath, and always compact it in layers with a whacker plate. Type 1 is a heavy beast — roughly 2 tonnes per cubic metre — so a tonne covers only about 9–10 m² at 50mm, and half that at a full 100mm. That density is exactly why guessing goes so badly wrong here; get your real figure from the MOT Type 1 calculator before you ring the merchant.
Hardcore
Hardcore is Type 1's rougher cousin — broken brick, crushed concrete, general crushed rock used to build up and fill before you cap it with something finer. Think of it as the bulk fill under a shed base or a big slab: it does the heavy lifting so you're not paying for expensive material to fill a deep hole.
Depth depends entirely on the job — anything from 100mm under a light base to several hundred millimetres filling a dig-out. It's a heavy fill, similar in density to Type 1, so budget your tonnage generously. The hardcore calculator will size it for your dig, and if you're capping it with concrete afterwards, keep the aggregate calculator handy for the sub-base layer too.
Crushed stone
Crushed stone is the all-rounder — angular chippings that lock together when compacted, which makes it brilliant for drainage, pipe bedding, and paths that need to stay put rather than scatter like round pea shingle. The angular edges are the whole point: they grip.
Depth is job-led — 50mm for a decorative or drainage layer, more where it's structural. Density sits in the same middleweight-to-heavy bracket as gravel and Type 1 depending on the stone, so a tonne lands in the same ballpark of 10-ish m² at 50mm. Firm it up with the crushed stone calculator.
Sharp sand & building sand
Sand is the great smoother — the bedding layer that lets you level block paving and slabs to a hair, and the key ingredient in mortar and screed. Sharp (grit) sand for bedding and concrete; soft building sand for mortar. Don't mix them up or your pointing will sulk.
For a paving bedding layer you're usually laying 30–50mm of sharp sand. It's a middleweight at roughly 1.6 tonnes per cubic metre. If you also need polymeric sand to lock the joints once the paving's down, that's a separate, thinner job — see the polymeric sand calculator. For the bedding quantity, the sand calculator is your friend.
Topsoil
Not a construction aggregate, but it's ordered by the tonne and worked out with the very same sum — so it belongs here. Topsoil fills raised beds, levels a lawn, and gives new planting something to actually grow in. Skimp on depth and your veg sulk; overdo it and you've barrowed soil you didn't need.
For a lawn or general levelling, 100–150mm is typical; for a raised bed or hungry veg patch, go deeper, 200–300mm. Topsoil is lighter than stone — roughly 1.3–1.5 tonnes per cubic metre — so a tonne covers a fair bit more ground than Type 1 would. Size it with the topsoil calculator, and for raised beds specifically the raised bed soil calculator handles the box maths for you.
Bark & mulch
The featherweight of the family. Bark and mulch dress borders, suppress weeds and lock moisture into the soil — a thin decorative-and-practical top layer rather than a structural one. Because it's so light, a tonne (or more usefully, a cubic metre) goes a very long way.
Lay it at 50–75mm (2–3in) to actually smother weeds — any thinner and they'll punch straight through. Mulch is sold and calculated by volume more than weight because it's so light, so work in cubic metres or litres here. The mulch calculator and the bark mulch guide have you covered.
Aggregate comparison at a glance
Rough rules of thumb only — density varies by supplier and stone size, so always confirm your real figure in the calculator before ordering.
| Material | Typical use | Usual depth | Approx. density (t/m³) | Weight class |
|---|---|---|---|---|
| Gravel / shingle | Paths, borders, driveways | 40–50mm | ~1.5–1.75 | Middleweight |
| MOT Type 1 | Sub-base under paving/drives | 100–150mm | ~2.0 | Heavy |
| Hardcore | Bulk fill / build-up | 100mm+ | ~1.8–2.0 | Heavy |
| Crushed stone | Drainage, bedding, paths | 50mm+ | ~1.5–2.0 | Middle–heavy |
| Sharp / building sand | Bedding, mortar, screed | 30–50mm | ~1.6 | Middleweight |
| Topsoil | Beds, lawns, levelling | 100–300mm | ~1.3–1.5 | Light–middle |
| Bark / mulch | Border dressing, weed suppression | 50–75mm | light (sold by volume) | Featherweight |
Ordering without the drama
A few hard-won habits. Always add 5–10% for wastage — settlement, spillage, uneven ground. If you're between a bulk bag and loose tipped, remember a "bulk bag" is usually around 800kg, not a full tonne, so don't assume. Measure twice, in metres, before you calculate — mixing feet and metres is how a two-tonne job becomes a six-tonne bill. And if a job needs two layers — say Type 1 then a gravel top — calculate each layer separately and add them up. The aggregate calculator is the quickest way to run the numbers for any material on this page.
FAQs
How much does a tonne of aggregate cover?
It depends entirely on the material and the depth. As a rough steer, a tonne of a middleweight like gravel covers around 10–14 m² at 50mm, while a heavy material like MOT Type 1 covers closer to 9–10 m² at the same depth. Halve the coverage if you double the depth. For your exact job, use the aggregate calculator.
What's the difference between MOT Type 1 and hardcore?
Type 1 is a graded, crushed stone made to a highway specification — consistent sizes that compact into a tight, load-bearing sub-base. Hardcore is rougher, more variable fill (broken brick, crushed concrete) used to bulk up and build height before you cap it. Use Type 1 directly under paving; use hardcore for deeper filling underneath.
How deep should a sub-base be for a driveway?
For a domestic driveway carrying a car, aim for around 100–150mm of compacted MOT Type 1, laid and whacked in layers. A footpath or patio needs less. Get the tonnage from the Type 1 calculator.
Should I order in tonnes or bulk bags?
Loose tipped by the tonne is usually cheaper for larger jobs; bulk bags suit smaller quantities and tight access. Just remember a bulk bag is often around 800kg rather than a full tonne, so factor that in when you compare prices and quantities.
Do I need to add extra for wastage?
Yes — add about 5–10%. Loose aggregate settles when compacted, you lose a little to uneven ground and spillage, and running short mid-job is a false economy. A spare barrow-load beats a second delivery charge.
## Free tools to put this into practice Reading is one thing — working out your own numbers is what saves time and money. Here are the free HowMuchDoINeed calculators that pair best with this guide: * **[Mot Type 1 Calculator](/calculators/mot-type-1-calculator)** — work out exactly how much you need and what it will cost. * **[Aggregate Calculator](/calculators/aggregate-calculator)** — get an instant materials estimate for your project. * **[Hardcore Calculator](/calculators/hardcore-calculator)** — size up quantities and costs before you head to the merchant. * **[Decorative Gravel Calculator Landscaping Guide](/blog/decorative-gravel-calculator-landscaping-guide)** — plan your order so you avoid over- or under-buying. Explore every [free calculator](/calculators) on HowMuchDoINeed — no sign-up required.