Tarmac Calculator
Find how many tonnes of tarmac you need for a drive, path or patch.
Measure your project
Your answer
That is 2.55 m³.
If you buy bags
A drive needs a firm base under the tarmac. The MPA gives 150 mm of hardcore, such as Type 1. Check your local building rules or ask a builder or engineer.
What it costs
Cold-lay: £13.80 a bag with VAT, from only 2 stores, so a rough guide. Laid by a pro: about £90 per m², the middle of 7 cost-guide figures (VAT not stated). Get local quotes.
Quick answers
- A 10 × 3 m drive, 85 mm thick
- About 5.99 tonnes of tarmac.
- Weight of 1 m³, rolled
- About 2.35 tonnes. Cemex gives 2.26 to 2.56 by mix, but its top figure may be high (see below).
- Layers for a drive
- 25 mm on top and 60 mm below, over 150 mm of base, says the Mineral Products Association.
- What one tonne covers
- About 17 m² at 25 mm thick. Heidelberg gives 14–18 m².
How to work it out
- Work out the area of the drive or path in m²: length × width.
- Choose the rolled thickness: one layer or both. Change mm to metres by dividing by 1,000.
- Area × thickness gives the m³ of finished tarmac.
- Rolled tarmac is about 2.35 tonnes per m³. So m³ × 2.35 gives the tonnes to order.
10 × 3 × 0.085 = 2.55 m³
2.55 × 2.35 = 5.99 tonnes
Tonnes of tarmac by drive size
Each row is one drive. The first two columns are single layers; the last adds both together.
| Drive | Top, 25 mm | Lower, 60 mm | Both, 85 mm |
|---|---|---|---|
| 5 × 3 m | 0.88 | 2.11 | 3.00 |
| 6 × 3 m | 1.06 | 2.54 | 3.60 |
| 8 × 3 m | 1.41 | 3.38 | 4.79 |
| 10 × 3 m | 1.76 | 4.23 | 5.99 |
| 10 × 5 m | 2.94 | 7.05 | 9.99 |
| 12 × 6 m | 4.23 | 10.15 | 14.38 |
Rolled thickness, with nothing extra for edges.
The layers of a tarmac drive
The Mineral Products Association (MPA) gives this build for a private drive:
- Top layer: 25 mm. This is the surface you see.
- Lower layer: 60 mm of a mix called AC 20.
- Base: 150 mm of hardcore, such as Type 1.
A UK government guide to front gardens gives 200–250 mm for a whole drive. It was written for drives that let rain soak through (permeable).
For a 10 × 3 m drive, the 150 mm base is about 9.4 tonnes of Type 1. Our Type 1 calculator works out yours.
Laying depth before the roller
Hot tarmac goes down loose and thick. The roller then presses it to its final depth. For dense mixes, the Asphalt Institute says to lay it about 1.25 times the finished depth. Open mixes sink less, about 1.15 times.
The weight you order does not change.
| Finished | Dense mix | Open mix |
|---|---|---|
| 25 mm | 31 mm | 29 mm |
| 60 mm | 75 mm | 69 mm |
| 85 mm | 106 mm | 98 mm |
Your drive will hold the weight of cars. Check your local building rules or ask a builder or engineer.
Tarmac per square metre
Supplier calculators, like Heidelberg's and Cemex's, work in tonnes. This table turns a thickness into kg per m², and m² per tonne.
| Thickness | Per m² | One tonne covers |
|---|---|---|
| 20 mm | 47 kg | 21.3 m² |
| 25 mm | 59 kg | 17 m² |
| 30 mm | 71 kg | 14.2 m² |
| 40 mm | 94 kg | 10.6 m² |
| 60 mm | 141 kg | 7.1 m² |
| 85 mm | 200 kg | 5 m² |
Heidelberg says a tonne covers 14–18 m² at 25 mm. Our figure sits inside that.
Why tonnes differ between mixes
Some mixes are heavier than others. Cemex gives a weight for each mix. Here is a 10 × 3 m drive at 85 mm with each one.
| Mix | Per m³ | Tonnes |
|---|---|---|
| AC open or medium (Cemex) | 2.26 t | 5.76 |
| Our figure | 2.35 t | 5.99 |
| HRA (Cemex) | 2.45 t | 6.25 |
| AC dense (Heidelberg) | 2.5 t | 6.38 |
| AC dense (Cemex) | 2.56 t | 6.53 |
Cemex's AC dense figure looks high next to its HRA figure. Heidelberg's calculator works out at about 2.5 for AC dense.
Ask your supplier which mix they will lay.
Cold-lay bags and what a laid drive costs
Cold-lay bags
Cold-lay tarmac comes in 25 kg bags. Wickes says one bag covers about 0.4 m² at 30 mm thick. Our middle price is £13.80 a bag. That is from only 2 stores, so treat it as a rough guide.
Bags add up fast on a whole drive. Here is a 10 × 3 m drive:
| Thickness | Bags | Weight | Cost |
|---|---|---|---|
| 30 mm (Wickes figure) | 75 | 1.9 t | £1,035 |
| 85 mm (scaled up) | 213 | 5.3 t | £2,939 |
Wickes gives cover at 30 mm only. The 85 mm row is our sum from that figure. Cost with VAT.
Having a drive laid
Cost guides give £40 to £130 per m² to lay a tarmac drive. Our figure, £90, is the middle of 7 figures from those guides.
They are guides, not quotes from firms. None of them say if VAT is included.
We opened 6 of the 7 guides again to check them. Those 6 alone give a middle of £92.50.
The top figure, £130, comes from MyBuilder. Its own page also gives lower prices, so it disagrees with itself.
At £90 per m², a 10 × 3 m drive would cost about £2,700. Get quotes from local firms.
We found no price per tonne for tarmac, so we don't show one.
Questions people ask
How much tarmac do I need?
Take the drive's area in m² and its rolled thickness in metres. Multiply them, then multiply by 2.35 for tonnes. Or type your sizes into the calculator above.
How do you calculate tarmac tonnage?
Work out m² × thickness in metres, then multiply by 2.35. A 10 × 3 m drive at 85 mm needs about 6.0 tonnes.
How much tarmac per square metre?
About 59 kg per m² for a 25 mm top layer. Both drive layers, 85 mm, take about 200 kg per m².
How much per square metre for tarmac?
Cost guides give £40–£130 per m² to have a drive laid, and don't say if VAT is in. The middle of 7 guide figures is £90. Get quotes from local firms.
How many m² does a tonne of tarmac cover?
About 14–18 m² at 25 mm thick, says Heidelberg Materials. Our sums give about 17 m².
What base do you need for tarmac?
The Mineral Products Association puts 150 mm of hardcore base under a tarmac drive. Check your local building rules or ask a builder or engineer.
How thick should a tarmac drive be?
85 mm in two layers, says the Mineral Products Association. That is 60 mm below and 25 mm on top.
How much does a bag of cold-lay tarmac cover?
About 0.4 m² at 30 mm thick, says Wickes, for a 25 kg bag.
Where our numbers come from
- Asphalt weight: Asphalt Institute (110 lb per square yard per inch)
- Tarmac coverage: Heidelberg Materials asphalt calculator (14–18 m² per tonne at 25 mm)
- Tarmac weight by mix: Cemex asphalt calculator
- Tarmac drive layers: Mineral Products Association, Asphalt Applications 1
- Drive depth: UK government front-garden paving guide
- Type 1 weight and price: Wickes 800 kg bag (checked Oct 2026)
- Cold-lay bag: Wickes Tarmac Cold Lay Macadam (25 kg covers about 0.4 m² at 30 mm)
- Cold-lay price: 2 UK stores (25 kg, Oct 2026)
- Laid tarmac price: the middle of 7 cost-guide figures (6 checked again; VAT not stated)
Made by BuildersCount. Last checked 3 Oct 2026.
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