Calculator
How much cable sand do I need?
Put in your trench and your ducts or cables. You get the sand in cubic metres, tonnes and bulk bags, with the space the ducts take up already taken off.
You need about
- Tonnes
- Bulk bags (about 850 kg)
- Sand, in cubic metres
An estimate to plan with. We check the amount with you when we price the job.
How the sum works
Length × width × sand depth gives the space to fill, in cubic metres. Each duct or cable takes up its own cross-section times the length, so that comes off. What is left is multiplied by 1.6 to 1.8 tonnes per cubic metre, the usual weight of compacted cable sand, then 10% is added for spillage and topping up.
Worked example. A 100 m trench, 450 mm wide, with 300 mm of sand, is 13.5 m³. Three 110 mm ducts take up about 2.85 m³ of it, leaving 10.65 m³ of sand. That is about 17 to 19 tonnes, or about 19 to 21 tonnes with 10% added: around 23 to 25 bulk bags, or about one tipper load.
The depths depend on the voltage and the network operator, so take them from your drawings. More on bedding and blinding in what cable sand is.
Questions
How many tonnes are in a cubic metre of cable sand?
Roughly 1.6 to 1.8 tonnes once it is laid and compacted, depending on the sand and how damp it is. That is why the calculator gives a range.
How many bulk bags is a tonne?
Our bulk bags hold about 850 kg, so a tonne is a little over one bag, and 20 tonnes is around 24 bags.
Why take the ducts off?
Ducts and cables take up space that would otherwise be sand. On a long run with several large ducts that can be a good few tonnes, so leaving it in means over-ordering.
Should I order extra?
A little, yes. Some sand is always lost to spillage, uneven trench bottoms and topping up after compaction. The calculator adds 10% unless you untick it.
Does it work for cement-bound sand?
Yes. Work it out the same way. If you are mixing CBS on site, the sand is nearly all of it, and you add the cement to the ratio your spec gives.