What this calculator works out
This calculator multiplies a bag count by bag size and applies a compression factor, giving the true volume of green waste once it is compacted.
Loose garden waste is mostly air. Six bags of prunings compress to considerably less than six bags of anything solid, which matters when booking a collection or a skip.
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Before you estimate
- Bag size varies. A standard garden waste sack is around 90 litres; builders' bags are much larger.
- Compression depends on the material. Soft leafy waste compacts to a third of its loose volume; woody prunings barely compress at all.
- 30% is a reasonable middle figure for mixed garden waste.
- Council green bins are usually 240 litres, which is less than three loose sacks.
Running woody prunings through a shredder reduces their volume by roughly three quarters and turns them into usable mulch rather than waste. Hiring a shredder for a day costs less than several skip loads and produces material worth having. For a garden with mature shrubs, it is often the cheapest route.
How this calculator works
Loose volume reduced by the compression factor:
Compacted litres = bags × bag size × (1 − compression ÷ 100)The compression figure represents how much of the loose volume disappears when the material settles or is compacted. It is a rough allowance rather than a measured property, and it varies enormously between soft and woody waste.
Worked example: six bags
Using the default figures — 6 bags of 90 litres with 30% compression:
- Loose volume: 540 litres
- Compacted: 378 litres
378 litres is more than one 240 litre council green bin and less than two. That kind of answer is the useful one — it tells you whether a job fits a fortnightly collection or needs a trip to the tip. For a larger clearance, 378 litres is around half a cubic metre, which is well within a mini skip.
Common mistakes
- Booking a skip on loose volume. Green waste compacts considerably.
- Using one compression figure for woody and leafy waste. They behave very differently.
- Putting soil and turf in a green waste collection. Most councils exclude them.
- Overfilling a green bin. Many councils will not empty a bin with a raised lid.
- Sending compostable material away. Much of it is better composted at home.
Frequently asked questions
What can go in a council green bin?
Typically grass, leaves, hedge trimmings, prunings, weeds and cut flowers. Usually excluded: soil, turf, stones, food waste in some areas, plant pots, and anything treated with persistent herbicides. Rules vary between councils, so check locally — contaminated loads are frequently rejected.
Should I compost it instead?
Where you can, yes. Most green waste is a resource rather than a problem, and home composting avoids both the collection charge and the transport. The exceptions are perennial weed roots, seeding weeds and diseased material, which need a hot heap or disposal elsewhere.
What about woody prunings?
They compost slowly whole and quickly shredded. A shredder turns them into mulch within an afternoon; without one, they can be stacked in a corner as a habitat pile, which supports a great deal of wildlife and needs no effort at all.
Can I burn garden waste?
It is legal in most circumstances but heavily constrained — you must not cause a nuisance with smoke, and local authorities can serve an abatement notice. Some areas have additional restrictions. Burning green material produces a great deal of smoke and destroys something that could improve the soil, so it is rarely the best option.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — garden waste collection, bonfires and household waste rules
- Royal Horticultural Society — composting and dealing with garden waste
Sources are checked at publication and can change — how I choose and check references.