We put a gravel driveway in at the front of our house a few years ago and the difference it made - visually and practically - was enormous. The old crumbling tarmac was replaced in a long weekend and has needed almost no maintenance since. What I underestimated at the time was how much gravel we actually needed. My initial estimate was off by about 40%, and we ended up having to order a second load halfway through.
The mistake was calculating gravel depth alone without properly accounting for the sub-base, and then being too conservative with the amount of surface gravel. Here is how to do it properly.
Types of gravel for driveways
Not all gravel is the same, and the type you choose affects both the price and the quantity calculation (different gravels have different densities).
Shingle / Gravel (10-20mm) - The most popular driveway choice. The larger, angular pieces stay put better underfoot and under tyres. Self-binding shingle with dust and fines in it compacts slightly and is even more stable. Standard rounded shingle is more decorative but moves around more.
Pea Gravel (6-10mm) - Neat, small, attractive. The problem is it moves. A lot. Fine for paths and garden borders, but for a driveway with regular traffic it will end up on your lawn and doorstep within months. I would not recommend it for driveways.
Slate Chippings - A premium decorative option. Beautiful blue-grey or purple colour. Works well on driveways where the look matters as much as function. Similar depth and quantity calculations to standard shingle.
Gravel Scalpings - A blend of fines and chips, cheap, compacts reasonably well. Not attractive as a sole surface but good as a secondary layer or for less visible areas.
Our Gravel Calculator has individual density values for each type so your quantity calculation is accurate for the specific material you are using.
How deep does gravel need to be?
The right depth depends on what is underneath the gravel.
| Situation | Recommended surface gravel depth |
|---|---|
| On a compacted MOT Type 1 sub-base | 50mm |
| On a compacted hardcore sub-base | 50-75mm |
| Directly on firm, well-compacted soil | 75-100mm |
| Decorative paths and garden borders | 40-50mm |
The golden rule: always use a sub-base. Gravel laid directly on bare soil will gradually disappear into the ground. Traffic and foot pressure push the stones down, roots and worms disturb the soil from below, and rain washes the fine material away. Within a couple of seasons you are looking at a thin, patchy mess that needs constant topping up.
A 100mm MOT Type 1 sub-base with a geotextile membrane underneath is the foundation for a gravel driveway that will look good for 10-15 years rather than 2-3.
The formula
Volume (m3) = Length (m) x Width (m) x Depth (m)
Weight in tonnes = Volume x density of gravel
Standard shingle has a loose density of approximately 1.7 t/m3. Pea gravel is slightly lighter (around 1.6 t/m3). Slate chippings are around 1.4 t/m3. The Gravel Calculator has accurate figures for each type.
Worked example - standard driveway
Driveway 10m x 4m, 50mm gravel surface layer:
- Volume = 10 x 4 x 0.05 = 2.0 m3
- Weight = 2.0 x 1.7 = 3.4 tonnes
- Add 10% wastage = 3.74 tonnes to order
That is around 4-5 bulk bags, or a small loose load delivery.
Gravel quantities by area and depth
| Area | 40mm depth | 50mm depth | 75mm depth |
|---|---|---|---|
| 5m2 | 0.37t | 0.47t | 0.71t |
| 10m2 | 0.75t | 0.94t | 1.41t |
| 15m2 | 1.13t | 1.41t | 2.12t |
| 20m2 | 1.50t | 1.89t | 2.83t |
| 30m2 | 2.24t | 2.83t | 4.25t |
| 50m2 | 3.74t | 4.72t | 7.08t |
Based on 1.7 t/m3 loose density, before 10% wastage.
Bulk bags vs loose load: which is better value?
Bulk bags are good for jobs under 4-5 tonnes. They are convenient, easy to stack and you can work through them at your own pace. Most garden centres and builders merchants stock them for collection. The downside is cost - per tonne, bulk bags are typically 15-25% more expensive than a loose load.
Loose tipper load is better for larger jobs. The material is cheaper per tonne, it gets delivered in one go, and there is no stacking, cutting and emptying bags to deal with. The downside is you need a suitable spot to have it tipped - ideally close to where you are working.
| Project size | Tonnes needed | Recommendation |
|---|---|---|
| Small path | Under 1t | Bulk bag(s) |
| Garden border / path | 1-2t | Bulk bags |
| Small patio or driveway | 2-4t | Bulk bags or loose |
| Standard driveway | 4-10t | Loose load |
| Large driveway | 10t+ | Loose load |
Do not forget the sub-base
Your gravel calculation is for the surface layer only. Before any surface gravel goes down, you need to calculate your sub-base separately.
For a 10m x 4m driveway with a 100mm compacted MOT Type 1 sub-base, you will need approximately 10-12 tonnes of MOT Type 1 in addition to your gravel. Use the Sub Base Calculator or MOT Type 1 Calculator to work that out.
The full build-up should be:
- Excavate to 200-250mm depth
- Compact the subgrade (natural ground)
- Lay geotextile membrane
- Compact 100-150mm MOT Type 1 sub-base
- Lay second geotextile membrane (optional but recommended)
- Spread and rake 50mm gravel surface layer
My tips for getting gravel right
Having done this a few times now, including one very expensive re-do on our front driveway, here is my honest advice:
Contain the edges properly. Gravel will migrate outward unless you stop it. Timber edging boards, metal gravel edging, block kerb or concrete edging boards all work. Without them, the edges gradually disappear into the lawn and borders and the driveway starts to look scruffy within a year or two.
Use self-binding gravel for high-traffic areas. Self-binding gravel contains a mix of sizes including dust and fines. When it gets wet and dries out, it almost sets into a firm surface. It reduces the amount of stone kicked up and tracked inside. Worth the small extra cost on a driveway.
Order your surface gravel after the sub-base is done. There is nothing worse than having a tipper load of shingle sitting on your front garden while you are still working on the sub-base. It seems obvious in retrospect.
10% wastage is the minimum. Some always ends up in the wrong place - in the borders, kicked over the edge, tracked inside. For a driveway I always add 12-15%, especially on a first project.
Rake it level while it is fresh. Once gravel has been driven on a few times it is much harder to redistribute. Get it level and at the right depth before anyone drives on it.
Use the Gravel Calculator to work out your quantities before ordering.