Rubber Mulch Calculator
The rubber mulch calculator below works out how many bags a bed or play area needs, and whether it pays for itself against wood mulch over ten years.
Landscape Bed
Playground Surfacing
Rubber has the best fall rating per inch of any common loose fill, six inches covers a ten foot fall.
Rubber vs Wood Over Ten Years
Rubber costs several times more up front and is not replaced. Wood is cheap and is replaced every year or two. This is where they cross.
How to use the Rubber Mulch Calculator
Set the depth lower than you would for wood. For a landscape bed, an inch and a half to two inches is enough, rubber does not decompose, so it does not need the three or four inches wood mulch is laid at.
For a play area, use the playground tab. The depth there is fall protection, set by the height a child can fall from, and rubber does better per inch than any other loose fill.
The comparison tab answers the real question: rubber costs several times more up front and is not replaced, wood is cheap and is replaced every year. Enter your own prices and see where they cross.
Rubber Mulch formula
volume = length × width × depthbags = cubic feet ÷ bag size, rounded upcubic yards = cubic feet ÷ 27
Bags are normally 0.8 cubic feet, around 40 lb.
| Depth | Coverage per 0.8 cu ft bag | Bags per 100 sq ft |
|---|---|---|
| 1 in | 9.6 sq ft | 11 |
| 1½ in | 6.4 sq ft | 16 |
| 2 in | 4.8 sq ft | 21 |
| 3 in | 3.2 sq ft | 32 |
| 6 in (playground) | 1.6 sq ft | 63 |
Loose-fill fall protection depths, for comparison:
| Material | Depth for a 10 ft fall |
|---|---|
| Shredded rubber | 6 in |
| Wood chips / engineered wood fibre | 9 in |
| Pea gravel | 12 in (rated to 8 ft) |
Worked example
A 20 ft × 10 ft bed at 2 inches, 5% waste:
- Area: 200 sq ft. Volume: 200 × 0.1667 = 33.3 ft³
- Plus 5%: 35 ft³ ÷ 0.8 = 44 bags (1.30 yd³)
A 20 ft × 15 ft play area at the 6 inch depth for a 10 ft fall height: 300 × 0.5 = 150 ft³, plus 10% = 207 bags.
Over ten years on that 200 sq ft bed, at $8 a rubber bag against $4 for a 2 cu ft wood bag replaced annually: rubber is $336 once (42 bags), wood $680 across ten applications, and rubber has paid for itself by year five.
What the result means
Rubber mulch is a ten-year decision, not a one-season one. It costs roughly five times what wood costs per cubic foot, and it does not rot, blow away or need topping up. On any bed you intend to keep, the arithmetic turns in its favour somewhere between years three and five, which is exactly what the comparison tab is for, with your own prices rather than assumed ones.
On playgrounds the case is about depth rather than money. Six inches of shredded rubber is rated for a ten foot fall where wood chips need nine inches and pea gravel twelve. Less excavation, less material, less topping up.
It is not a soil amendment. Wood mulch breaks down and feeds the soil; rubber never does. For vegetable beds and anywhere you want the soil to improve, wood is the right answer and no cost comparison changes that.
Common mistakes
- Laying it as deep as wood mulch. Rubber does not decompose, so an inch and a half to two inches is plenty in a bed. Three or four inches is wasted money.
- Using it where you want soil improvement. Rubber adds nothing to the soil, ever. Vegetable beds and new plantings want wood.
- Comparing sticker prices. Per bag rubber looks absurd. Per decade it usually is not. Compare over the life of the bed.
- Skipping the fabric. Weeds coming up through rubber are far harder to deal with than weeds in wood, because you cannot just turn it over.
- Assuming it never needs attention on a playground. It still displaces under swings and slides and still has to be raked back to depth for the fall rating to mean anything.
Frequently asked questions
How much rubber mulch do I need?
A 0.8 cubic foot bag covers 4.8 square feet at 2 inches deep, so about 21 bags per 100 square feet. A 20 by 10 foot bed at 2 inches takes 44 bags including a 5 percent allowance.
How deep should rubber mulch be?
An inch and a half to two inches in a landscape bed, less than wood mulch, because it does not decompose. For playground fall protection it is 3 inches for falls up to 6 feet and 6 inches up to 10 feet.
Is rubber mulch cheaper than wood in the long run?
Usually, on a bed you keep. Rubber costs several times more up front but is not replaced; wood is topped up every year or two. On a 200 square foot bed at typical prices, rubber runs $336 once against $680 for ten years of wood. The crossover is normally between years three and five.
How long does rubber mulch last?
Around ten years or more. It does not rot or break down, though colour fades over time and material displaces from high-traffic areas and needs raking back.
How much does a bag of rubber mulch cover?
A standard 0.8 cubic foot bag covers 9.6 square feet at 1 inch, 4.8 at 2 inches, 3.2 at 3 inches and 1.6 at the 6 inch playground depth.
Is rubber mulch better than wood chips for a playground?
For fall protection per inch, yes, 6 inches of shredded rubber matches a 10 foot fall height where wood chips need 9 inches. It also does not compact or decompose. It does not improve soil and costs more up front.
Sources and assumptions
Volume is exact geometry. Coverage figures follow from the standard 0.8 cubic foot bag.
Loose-fill fall protection depths follow the US Consumer Product Safety Commission public playground safety handbook, which rates shredded rubber more highly per inch of depth than wood fibre or pea gravel.
Bag weight of roughly 40 lb is a manufacturer figure; published bulk densities for shredded rubber vary widely, which is why this page works in volume and bags rather than tons.
Cost comparisons use whatever prices and replacement interval you enter, and exclude fabric, edging and labour.