Playground Mulch Calculator
Safety surfacing yards, maintained depth, and fall verdict from area and material.
What it does
Playground surfacing works by depth: 9 inches of maintained wood chips cushions falls to 10 feet, while the same depth of sand only covers 4. Fresh fill goes 12 deep because use compacts a quarter away.
The tool above takes material with play area and equipment height. It returns cubic yards to order with maintained depth and a fall verdict beside them.
The default of 400 ft2 of wood chips under 7 ft equipment needs 14.81 yd3 initial at 12 in, maintained 9 in, protecting this equipment to its 10 ft rating. Sand under 5 ft equipment fails at 4 ft: upgrade.
The depths follow federal playground safety handbooks with the current edition matching each figure. Both fix 12 in initial for 9 maintained and rate chips to 10 ft, mulch to 7, gravel to 5, sand to 4.
How to use
- Pick the surfacing material planned.
- Measure the play area edge to edge.
- Enter the highest equipment fall height.
- Order the initial yards for 12 in fill.
- Maintain 9 in forever with marked posts.
Formula
- 12 / 9
- Initial versus maintained inches (25% compacts).
- 27
- Cubic feet per cubic yard.
- rating
- Max fall feet each material protects.
Rubber mulch skips compaction math at 6 in to 10 ft. Borders must contain the fill, and drainage decides how long depths hold.
Worked example
Example: 400 ft2 wood chips, 7 ft falls
Defaults: chips, 400 ft2, 7 ft.
- Initial: 400 x 1 ft / 27 = 14.81 yd3.
- Maintain 9 in compressed against marked posts.
- Rating: chips protect to 10 ft, above 7.
- Drainage and borders hold the depth.
- Tool shows 14.81 yd3 initial (12 in), 9 in maintained, protects verdict.
Reference table
| Material | Protects to | 400 ft2 needs |
|---|---|---|
| Wood chips | 10 ft | 14.81 yd3 |
| Wood mulch | 7 ft | 14.81 yd3 |
| Pea gravel | 5 ft | 14.81 yd3 |
| Sand | 4 ft | 14.81 yd3 |
| Rubber mulch | 10 ft | 7.41 yd3 |
Limits
- Planning math; certified installers decide critical falls.
- Displacement concentrates under swings and slides.
- Frozen ground lowers winter protection.
- Never place loose fill over bare concrete.
Common mistakes
- Ordering maintained depth instead of initial fill.
- Letting levels slide below 9 in unnoticed.
- Sand under tall equipment it cannot cover.
- Skipping borders that hold the fill in.
- Ignoring drainage that rots and compacts fill.
Try it yourself
Quick checks. Answers sit tucked under each question.
Sand under 5 ft equipment?
Upgrade: sand protects to 4 ft only.
Rubber mulch for 400 ft2?
6 in depth: 400 x 0.5 / 27 = 7.41 yd3, protects to 10 ft.
Why 12 in initial?
Use compacts 25%: 12 settles toward maintained 9.
Questions
How deep should playground mulch be?
12 in fresh, maintained at 9 in compressed (rubber 6 in).
How much for 400 ft2?
400 x 1 ft / 27 = 14.81 yd3 initial of chips or mulch.
Which material is safest?
At rated depths chips and rubber cover 10 ft falls, mulch 7, gravel 5, sand 4.
Why refill often?
Use displaces fill fastest under swings and slide exits.
Grass safe enough?
No. Grass, dirt, and asphalt never qualify as protective surfacing.
Rubber different?
It barely compacts: 6 in protects to 10 ft with displacement watch.
Sources
- CPSC: Public playground safety handbook 2025 (PDF)
- CPSC: Outdoor home playground safety handbook (PDF)