How Much Tarmac Do I Need?
Whether you are laying a brand-new driveway from scratch or patching a pothole, ordering the correct quantity of tarmac is critical. Order too little, and you will be forced to halt work mid-job, resulting in a cold joint that ruins the aesthetic and structural integrity of the drive. Order too much, and you lose money, as hot mix tarmac cannot be stored and saved for later use once it arrives.
Our calculator takes the guesswork out of the material order by utilizing the industry-standard density equations for hot asphalt to give you a reliable tonnage figure.
Understanding Compaction and Density
When calculating tonnage, you must remember that hot tarmac is supplied loose but compacted heavily upon installation using a vibrating roller.
- Volume First: The calculation always begins by finding the fundamental volume: Area × Depth. Make sure all your units are consistent (e.g., all converted to metres) before multiplying.
- The Density Factor: The volume is then multiplied by the density of the material. Standard dense bitmac typically weighs around 2.4 tonnes for every 1 cubic metre of volume.
- Compacted Depth: The depth you input into the calculator should be your final requested compacted depth. Contractors usually lay the material roughly 20-25% thicker than the target depth to account for the compression of the roller.
Frequently Asked Questions
How do you calculate tarmac tonnage?
To calculate tarmac tonnage, you multiply the surface area (in square metres) by the compacted depth (in metres) to find the total volume in cubic metres. Then, multiply that volume by the density of the tarmac, which is typically around 2.4 tonnes per cubic metre.
How much does 1 tonne of tarmac cover?
At a standard surface course depth of 30mm, one tonne of tarmac will cover approximately 14 square metres. If laying a much thicker 75mm base/binder course, one tonne will only cover about 5.5 square metres.
What density is tarmac?
The density of compacted hot mix asphalt or tarmac varies slightly based on the aggregate used, but the universally accepted industry standard for estimation calculations is 2.4 tonnes per cubic metre (or 2400 kg/m³).
Why do I need to add wastage?
You should always add roughly 5% to 10% extra material onto your final calculation. This accounts for variations in the sub-base depth, material spilled over edging during spreading, and unrecoverable material left in the delivery lorry.
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