The limit is what the lorry can lift, not what the skip holds
Every skip company has a calculator on its website. Put a bathroom rip-out into one and it will suggest a 12 yard skip, because 12 yards is enough volume.
Then the lorry arrives and cannot pick it up.
A skip lorry lifts the skip off the ground with a hydraulic arm and a chain, and that arm has a working limit: typically around 8 tonnes, varying by vehicle. An 8 yard skip is 6.1 cubic metres, and filled with soil at about 1.4 tonnes a cubic metre that is 8 to 9 tonnes. At or past the limit, with the skip already full and on your drive.
It is not a fine and it is not a rule anybody can waive. It is a hydraulic arm. The lorry tries, fails, and leaves, and you pay for the journey.
For heavy waste the answer is more skips, not a bigger one
This is the whole point of the tool, and it is the opposite of what a volume calculator tells you.
Soil, clay, rubble, concrete, hardcore: all of them hit the lift limit well before they fill a large skip. So the tool lists every size with a verdict against it: what it weighs full, whether that lifts, and if not, how full you can actually fill it.
A 6 yard is generally the biggest that can be filled to the rim with soil, and it is why you see it on groundworks jobs everywhere, mistaken for whatever happened to be available.
And the hole is smaller than the spoil
If you are digging rather than stripping out, there is a second thing stacked on top: excavated ground bulks. Clay comes out about a third bigger than the hole it came from, broken rock by half.
So a 6 cubic metre excavation produces around 8 cubic metres of spoil, weighing 11 tonnes, and it is the 8 that has to fit in skips. The tool does that conversion first and shows you both figures. There is more on bulking here.
Level loaded, always
A skip must be level loaded to travel on a public road. Anything above the rim gets taken off before it goes, or the skip does not go.
Which means the usable volume is the volume to the top edge and not to the top of a heap, and it is why a skip always looks like it should hold more than it does. Every figure on this page is to the rim.
Where skips stop making sense
Past roughly fifteen cubic metres, a grab lorry or a muck away contract is usually cheaper per tonne and does not need road space, a permit and lights for a week.
Skips win on small jobs, on staged jobs where the waste appears over a fortnight, and anywhere a lorry cannot realistically get back twice. Grabs win on volume and on anywhere with room to stand.
Whether you need a permit for the road
Whether you need a permit. On a public road, yes, from the council, usually arranged by the skip company. On your own drive, no. That is a local question and the operator will know it better than any calculator.
Whether the material is contaminated. Made ground can carry a disposal cost that has nothing to do with volume, and skip operators are entitled to refuse it or charge for it separately. If the site has industrial history, that is a question for a lab.
Lift limits and skip volumes here are typical figures. Your operator's are the ones that matter, and the box on the tool is there to put theirs in.
Common questions
What size skip do I need for soil?
Smaller than you think, and this is the thing skip companies’ own calculators get wrong. A skip lorry lifts the skip with an arm that has a limit, typically around 8 tonnes. An 8 yard skip filled with soil is roughly 8 to 9 tonnes, which is at or past it. For soil and rubble the practical answer is a 6 or 8 yard filled part way, or several of them: not a bigger skip.
Why will they not collect my full skip?
Because the lorry physically cannot lift it. It is not a fine or a rule, it is a hydraulic arm and a chain with a working limit. The lorry turns up, tries, and leaves, and you still pay for the wasted journey. Heavy waste in a large skip is the usual cause.
How many cubic metres in a skip?
A cubic yard is 0.765 cubic metres, so a 6 yard skip is 4.6 cubic metres and an 8 yard is 6.1. Those are nominal and operators differ. Note it is the volume to the rim, not to the top of a heap: a skip must be level loaded to go on a road.
Can I fill a skip above the top?
No. Skips must be level loaded to travel on a public road, so anything above the rim either gets taken off before it leaves or the skip does not go. The usable volume is the volume to the top edge, which is why a skip always looks like it should hold more than it does.
Skip or grab lorry?
Past roughly fifteen cubic metres a grab lorry or a muck away contract is usually cheaper per tonne, and it does not need road space and a permit for a week. Skips win on small jobs, staged jobs, and anywhere a lorry cannot get to twice.
Do I need a permit?
If the skip is going on a public road rather than on your own drive, yes: from the council, usually arranged by the skip company, and it will want lights and markings. On a private drive you do not. That is a local question and the skip company will know it better than any calculator.