How Much Aggregate Do I Actually Need?

Ordering aggregate is one of those jobs that sounds simple until you actually have to do it.

You know the size of the driveway. You know you need MOT Type 1. Then somebody asks how many tonnes you want and suddenly you are standing in the garden with a tape measure, a calculator and absolutely no idea whether the answer is two tonnes or twelve.

The good news is that working out how much aggregate you need is fairly straightforward once you know three things: the area you are covering, how deep the material needs to be and what type of aggregate you are ordering.

Here is a practical way to get it right without turning your weekend project into a maths lesson.

Start with the size of the area

Measure the length and width of the space in metres and multiply them together.

A driveway measuring 6 metres long by 3 metres wide has an area of:

6m × 3m = 18m²

For an awkwardly shaped area, split it into a few simple rectangles, calculate each one separately and add them together. You do not need millimetre-perfect measurements, but it is worth taking the time to measure properly rather than guessing.  The next question is where most people get caught out.

How deep does the aggregate need to be?

That depends entirely on what you are building.  A decorative layer of gravel might only need to be around 40–50mm deep. A path or patio sub-base will usually need considerably more, while a driveway carrying vehicles needs a properly prepared and compacted base.

As a rough starting point, you might be looking at:

These are working estimates rather than universal rules. The condition of the ground, the finished surface and the weight the area needs to carry all make a difference.

A driveway built over firm, well-prepared ground is a very different job from one being constructed over soft or unstable soil.

So how much MOT Type 1 do I need for a driveway?

This is probably the question we hear most often.

Let us use that 6m by 3m driveway again.

The area is 18m².

If you are installing MOT Type 1 at a compacted depth of 150mm, convert the depth into metres first:

150mm = 0.15m

Then calculate the volume:

18m² × 0.15m = 2.7m³

As a simple rule of thumb, a cubic metre of MOT Type 1 is roughly around two tonnes, although the exact weight varies depending on the material and how it is supplied.

That would put our example driveway at roughly:

2.7m³ × 2 = 5.4 tonnes

In the real world, you would normally want a little margin for uneven ground, settlement and compaction rather than ordering exactly 5.4 tonnes and hoping the calculations survive contact with reality.

For this particular job, ordering somewhere around 5.5 to 6 tonnes would therefore be a sensible starting point.

A quicker MOT Type 1 rule of thumb

For rough planning, one tonne of MOT Type 1 will cover approximately:

10m² at 50mm deep

5m² at 100mm deep

Around 3–3.5m² at 150mm deep

These figures are useful when you are trying to get an initial idea of quantities, but we would still recommend measuring the actual area before placing an order. Being one tonne short halfway through a job is frustrating. Having four tonnes left sitting outside your house is arguably worse.

Do not forget about compaction

One of the most common mistakes when ordering MOT Type 1 is calculating the finished volume and forgetting that the material will compact.

You are not simply tipping loose stone into a hole until it reaches the right height. The sub-base needs to be properly compacted to create a solid foundation, usually in manageable layers rather than attempting to compact a large depth all at once.

This is also why ordering aggregate purely by looking at the size of the pile can be misleading. A loose load will settle significantly once it has been spread and compacted.

Build a sensible allowance into your calculation, particularly if the ground underneath is uneven.

It is also worth planning what happens to the material you dig out. Excavating for a proper sub-base can generate a surprising amount of soil and spoil, and it is far easier to arrange a skip or muck-away collection before you start than to work around a growing heap of earth halfway through the job.

What about gravel?

Decorative gravel is normally laid much thinner than a structural sub-base, so you will need considerably less material.

Imagine you have a 20m² front garden that you want to cover with gravel at a depth of 50mm.

The calculation is:

20 × 0.05 = 1m³

The exact tonnage will depend on the type and size of stone you choose, but this gives your supplier the information needed to recommend an appropriate quantity.

It is also worth remembering that the MOT Type 1 underneath and the decorative gravel on top are two separate calculations. Do not calculate the full depth of the driveway and order the whole lot as decorative stone unless you particularly enjoy spending money.

Bulk bags or a loose load?

For a small garden job, one or two bulk bags can be convenient. Once the quantities start increasing, however, having aggregate delivered loose can often make much more sense.

The right option will depend on how much you need, where the delivery can be tipped and how you plan to move the material around the site.

Before ordering, think about access. A tipper or grab lorry needs somewhere safe to stop and somewhere suitable to tip the load. If you are unsure whether access will be a problem, it is much better to discuss it before the lorry arrives.

The easiest way to avoid ordering the wrong amount

Measure the length and width of the area, decide roughly how deep the material needs to be and have that information ready when you request a quote.

You do not necessarily need to work out the exact tonnage yourself.

At Select A Skip, we can arrange the delivery of MOT grade stone, sand, gravel, limestone, soils and other aggregates in quantities to suit everything from a garden project to a larger construction job.

Tell us what you are working on, the dimensions of the area and what you are planning to put on top. We can help you work out what you are likely to need and arrange delivery through our nationwide network of local suppliers.

That is a much better option than guessing, ordering twice or ending the project with a small mountain of stone that you now need to find another use for.

Need aggregate delivered for an upcoming project?

Get in touch with Select A Skip or call 01743 341 000 to discuss what you need and arrange a quote.

Frequently asked questions

How much MOT Type 1 do I need for a driveway?

Multiply the area in square metres by the depth in metres to get the volume, then multiply by roughly two to get the tonnage. For example, an 18m² driveway at 150mm (0.15m) deep needs about 2.7m³, or roughly 5.4 tonnes, before adding a small margin for compaction.

How many square metres does a tonne of MOT Type 1 cover?

As a rough guide, one tonne of MOT Type 1 covers around 10m² at 50mm deep, 5m² at 100mm deep, or about 3 to 3.5m² at 150mm deep. Exact coverage varies with the material and how it is compacted.

How much does a cubic metre of aggregate weigh?

A cubic metre of MOT Type 1 is roughly around two tonnes, though the exact figure varies by material type and whether it is measured loose or compacted.

Should I order aggregate in bulk bags or as a loose load?

Bulk bags suit small garden jobs, while a loose tipped load is usually more practical once quantities increase. The best option depends on how much you need, delivery access and how you plan to move the material on site.

How do I avoid ordering too much or too little?

Measure the length and width of the area, decide on the depth and have those figures ready when you request a quote. A supplier can then help confirm the tonnage, which is more reliable than estimating by eye.