Read this before the arithmetic
Playground surfacing is not a materials estimate with a safety label on it. It is a safety system that happens to be bought by the cubic yard. Falls to the surface are the leading cause of playground injuries serious enough to be treated, and what stands between a fall and an injury is the shock-absorbing performance of the material under the child, at the depth it happens to be at that moment, at the spot where the child lands.
That is why the depth field on this page has no default. There is no honest number to put there, because the correct depth is a property of three things this calculator cannot know: the material you are buying, the tested critical fall height that material achieves at a given depth, and the fall height of your equipment. The surfacing manufacturer publishes the first two and the equipment manufacturer publishes the third. Current national playground safety guidance sets out how the fall height and the use zone are determined. Get the numbers from those sources, write them down, and put the depth into the calculator. Anything else is guessing with a child underneath.
A second thing worth being plain about: a home playground is not certified by anyone. Public playgrounds are designed, installed and inspected against a standard by people whose job it is. A set of equipment bolted together in a back garden has none of that, and the person responsible for whether the surfacing is adequate on any given afternoon is you.
Loose fill moves, and moving is the whole problem
Loose fill — engineered wood fibre, wood chips, sand, pea gravel, shredded rubber — absorbs impact because it is loose. That is also its failure mode. It compacts under its own weight in the weeks after installation. It compacts harder under traffic. And it gets displaced, kicked and scuffed out of exactly the places that matter most: the arc under a swing, the run-out at the bottom of a slide, the landing at the end of a fireman's pole. Those are the highest-energy landing spots on the whole structure and they are the first to go thin.
The consequence is that installed depth and effective depth are different numbers, and only the second one protects anyone. A play area filled to the correct depth in April can be substantially shallower under the swings by July without looking any different from ten feet away. Raking the material back into the worn zones and topping up the volume are maintenance tasks with a safety function, not tidiness. The compaction allowance in this calculator buys the material to do that; it does not make the first fill deeper or safer.
What the calculator is actually doing
The area comes either straight from you, or from an equipment footprint with a use zone extended all round it. Then volume is area times depth in feet, and cubic yards is that divided by 27. A 24 by 20 foot area at nine inches is 480 times 0.75, which is 360 cubic feet, or 13.3 cubic yards before any settlement allowance. That is a large delivery and it arrives as one pile.
The rectangular use zone model is a simplification and you should know where it breaks. Swings are the clear case: the zone in front of and behind a swing extends much further than the zone at its sides, because a child leaves a swing travelling forward at speed. Slides have a run-out zone off the end. Spinning and rocking equipment has its own geometry. If your structure includes any of those, the rectangle here will understate the area, sometimes badly. Take the zone shape from the equipment manufacturer and use the direct-area option with a figure you have drawn out on the ground.
Drainage, edging and the base under it
Loose fill sitting in a hollow that holds water compacts into a mat, freezes solid in winter and stops behaving like loose fill at all. The area needs to drain, which usually means a permeable base and somewhere for water to leave. Edging holds the depth at the perimeter, because without it the material migrates outward and the edge of the use zone — where a child rolling from a fall ends up — becomes the shallowest part of the whole area. The drain slope calculator covers the fall you need if you are running a drain out of the area.
Do not confuse this material with landscape mulch. Bark mulch bought for flower beds is a different product with different particle sizing and no tested impact performance, and the mulch calculator exists for that job and only that job. Engineered wood fibre for play areas is manufactured to a specification precisely because the fibre size and shape are what make it knit and absorb. If you want a play area, buy the play product, and keep the paperwork that says what it was tested to.
Where to go instead of here
For fall height, use zone geometry and what makes a surface adequate, go to the current national playground safety guidance and to the manufacturer of your equipment. For depth, go to the surfacing manufacturer with your fall height and ask for the tested critical fall height of the product at each depth they sell. This page will convert their answer into cubic yards and a delivery weight, and that is the limit of what it should be asked to do. If you are also levelling and preparing the ground, the excavation volume calculator handles the dig and the topsoil calculator handles what comes off it.
Questions people ask
How deep should playground mulch be?
This page will not answer that, and you should be suspicious of any page that does with a single number. The depth that provides protection depends on the material, the depth at which that specific material has been tested, and the fall height of your equipment, which is the height of the highest designated play surface a child can stand on. The surfacing manufacturer publishes tested critical fall height figures at each depth for their product. Ask them, using the fall height from your equipment manufacturer. Then put their answer in the depth field here to get the volume.
Why does the calculator have no default depth?
Because a default becomes an answer. Every other field on this site has a sensible starting value, and on every other page that is helpful. Here it would be actively dangerous, because a number that appears without you having thought about it is a number you will not question, and this is the one field where the thinking is the point. Falls to the surface are what injures children on playgrounds. The depth is the protection. It has to come from a tested source that knows your material and your fall height.
How often does loose fill need topping up?
More often than people expect, and unevenly. The material compacts steadily for the first season and then displaces continuously wherever children land or drag their feet. Under swings and at the bottom of slides it goes thin fastest, and those are the worst places for it to be thin. Treat raking as a regular job rather than an occasional one, check the depth in the worn spots rather than in the middle where nothing happens, and buy material to bring it back rather than levelling the same reduced volume across the area. The depth on the day of the fall is the only depth that matters.
Is a rectangular use zone good enough for a swing set?
No. Swings are the specific case the rectangle gets wrong. A child leaving a swing travels forward, and the zone in front of and behind a swing extends much further than the zone to either side. A rectangle drawn around the equipment footprint will substantially understate the area you need to surface. Get the zone geometry from the equipment manufacturer, mark it out on the ground, measure the actual area, and use the total-area option in this calculator instead of the footprint option.
Can I use bark mulch from the garden centre?
It is a different product. Engineered wood fibre made for play areas is manufactured to a particle specification because the size and shape of the fibres are what make the material knit together and absorb impact, and it is tested and sold with published critical fall height performance at stated depths. Landscape bark is sold to look good and suppress weeds, with no such testing behind it. If the surfacing is there to reduce injury from falls, buy the product that has been tested for that and keep the documentation. Use the mulch calculator for beds and borders.