Mulch Calculator
Find out how much mulch you need for flower beds and landscaping, in cubic yards and 2 or 3 cubic foot bags.
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How to Calculate
Cubic yards = area (ft²) × depth (in) ÷ 324. One cubic yard covers 108 ft² at 3 inches.
Bagged mulch is usually sold in 2 ft³ bags; 13.5 bags equal one cubic yard.
Apply 2–4 inches. Thicker layers can suffocate roots; keep mulch a few inches away from stems and trunks.
See our methodology for how every calculator on this site is built.
Worked Example: Two Front Beds
A house with a bed along the front 30 ft long and 4 ft deep, plus a corner bed 12 ft by 6 ft. You want a 3 inch layer.
- Bed 1: 30 × 4 = 120 ft²
- Bed 2: 12 × 6 = 72 ft²
- Total area: 192 ft²
- Cubic yards: 192 × 3 ÷ 324 = 1.78 yd³
- Cubic feet: 1.78 × 27 = 48 ft³
- Bags: 48 ÷ 2 = 24 bags of 2 ft³, or 48 ÷ 3 = 16 bags of 3 ft³
If the beds already have an inch of old mulch, you only need 2 inches on top: 192 × 2 ÷ 324 = 1.19 yd³, which is 16 bags of 2 ft³. Measure what's there before you buy.
For curved or round beds, use the circle formula. A ring around a tree with a 4 ft radius is 3.14 × 4 × 4 = 50 ft². Irregular beds can be split into rough rectangles and triangles. Nobody needs it to the square foot.
Coverage of One Cubic Yard
| Depth | Area covered by 1 yd³ | 2 ft³ bags per 100 ft² |
|---|---|---|
| 1 in | 324 ft² | 4.2 |
| 2 in | 162 ft² | 8.3 |
| 3 in | 108 ft² | 12.5 |
| 4 in | 81 ft² | 16.7 |
Choosing a Mulch
Shredded hardwood is the default in most of the US. It knits together, stays on slopes and breaks down into the soil within about a year. Pine bark nuggets last longer but float and wash out in heavy rain. Pine straw is common in the Southeast, covers well and is sold by the bale rather than by the yard; a bale usually covers somewhere around 40 to 50 ft² at 2 to 3 inches. Dyed mulch holds color for one season and then fades like anything else.
Mistakes I See Every Spring
Volcano mulching
Piling mulch up against tree trunks keeps the bark wet, invites rot and rodents, and can lead to girdling roots. Keep it pulled back 3 to 6 inches from trunks and 1 to 2 inches from shrub stems. The ring should look like a donut, not a cone.
Laying it too thick
Every year people add 3 more inches on top of last year's 3 inches. After a few years the beds are a foot deep in wood and the roots are struggling for air. Top up to the depth you want, don't add a full layer by habit.
Mulching over weeds
Mulch suppresses seeds; it does not kill established perennial weeds. Pull or spray them first. A layer of plain cardboard under the mulch on a new bed helps a lot and rots away on its own.
Bags that sat in the sun
Bagged mulch that sat wet and sealed can go sour and smell like vinegar or ammonia. That can burn tender plants. If a bag smells strong, spread it out in a thin layer to air for a day first.
Rough Cost
Bulk shredded hardwood typically runs around $30 to $50 per cubic yard at a landscape supply yard, with premium and dyed mulches higher. Bagged mulch is often $3 to $6 per 2 ft³ bag, which works out to roughly $40 to $80 per yard. Delivery fees vary widely, so for a single yard it can make sense to pick up with a pickup truck, which holds about 1 to 2 yards of mulch depending on bed size.
Sources
Common questions
- How many bags of mulch do I need for 100 square feet?
- How much mulch do I need for a 5x20 flower bed?
Frequently Asked Questions
How deep should mulch be?
2–3 inches for most beds, up to 4 inches for weed control in open areas.
How many bags of mulch are in a yard?
13.5 bags of 2 ft³ or 9 bags of 3 ft³ make one cubic yard.
Is bulk mulch cheaper than bags?
Usually yes once you need more than 2–3 cubic yards, even with a delivery fee.
Should I remove old mulch before adding new?
Not usually. Rake it to loosen any matted crust and top it up by an inch or two. Remove it only if the total depth is already over 4 inches.
How often should mulch be replaced?
Shredded hardwood breaks down in about a year and needs a refresh each spring. Bark nuggets and pine straw last 2–3 years; rubber and stone last much longer.