How to use the mulch calculator
Pick the shape of your bed, enter its size and the depth you want. For a ring around a tree, choose Circle and enter the ring's diameter. If you have several beds the same size, such as a row of tree rings, set the number of beds instead of running the calculator again.
Refreshing old mulch? Enter how much is still there. Mulch breaks down, so a bed laid at 3 inches last year might have 1 to 2 inches left. The calculator only counts the difference.
The formula
cubic feet = area (ft²) × (target depth − existing depth) in ft
cubic yards = cubic feet ÷ 27
bags = cubic feet ÷ bag size (rounded up)
Worked example: a 20 × 10 ft bed, 3 inches deep
- Area: 20 × 10 = 200 ft².
- Volume: 200 × (3 ÷ 12) = 50 ft³.
- Add 5% for settling: 50 × 1.05 = 52.5 ft³, which is 52.5 ÷ 27 = 1.94 yd³.
- Bags: 52.5 ÷ 2 = 26.25, so 27 bags of 2 ft³, or 52.5 ÷ 3 = 17.5, so 18 bags of 3 ft³.
How deep should mulch be?
| Where | Depth | Notes |
|---|---|---|
| Flower and shrub beds | 2-3 in | The standard extension recommendation for bark and wood mulch |
| Around trees | 2-3 in | Keep it a few inches off the trunk; no "mulch volcanoes" |
| Fine mulch, compost | 1-2 in | Fine material mats down and can shed water |
| Coarse wood chips, paths | 3-4 in | Coarse chips stay open and let air through |
| Yearly top-up | About 1 in | Check what's left before you buy |
Bags or bulk?
Bags are easy to carry and store, and the price is fixed. Bulk mulch, delivered or picked up by the scoop, usually costs less per yard once you need more than two or three yards, but delivery fees can wipe out the savings on a small order. Enter both prices to see which is cheaper for your job.
One cubic yard of bulk mulch fills a normal pickup bed about level. A standard wheelbarrow holds 4 to 6 cubic feet, so a yard is roughly five to seven barrow loads.
Measuring tips and mistakes to avoid
- Irregular beds: break them into a rectangle plus a triangle or semicircle, or pace out the longest length and the average width. Mulch is forgiving, so close is good enough.
- Don't subtract plants. Shrubs and perennials take up little space at ground level. The settling allowance covers them.
- Don't pile it against trunks. Mulch heaped against bark holds moisture against the tree and invites rot and rodents.
- Fresh wood chips and nitrogen: on top of the soil they're fine for established plants. Avoid mixing fresh chips into planting holes.
Questions people ask
How many bags of mulch make a yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet (buy 14) or exactly 9 bags of 3 cubic feet.
How much area does a yard of mulch cover?
At 3 inches deep, one cubic yard covers 108 square feet. At 2 inches it covers 162 square feet, and at 4 inches 81. Divide 324 by the depth in inches.
How deep should mulch be?
University extension services generally recommend 2 to 3 inches of organic mulch for beds, and keeping it a few inches back from plant stems and tree trunks. Thicker than 4 inches can starve roots of air.
How many bags of mulch do I need for a 10x10 area?
At 3 inches deep, a 10 × 10 ft bed needs 25 cubic feet: 13 bags of 2 cubic feet or 9 bags of 3 cubic feet.
Is bulk mulch cheaper than bags?
Usually, once you need more than two or three cubic yards. Compare the bag total with a delivered bulk price per yard, including the delivery fee, by entering both prices above.
How much does a yard of mulch weigh?
Roughly 400 to 800 lb depending on the wood and how wet it is. Fresh, wet hardwood mulch is at the heavy end.
Sources and assumptions
- Michigan State University Extension: mulch, do it right
- Bag counts use the volume printed on the bag (27 ft³ per cubic yard). Weight uses 600 lb per cubic yard, the middle of the typical 400-800 lb range for wood mulch.
Last reviewed 26 October 2026. Every formula on this page is checked against the worked example above in our automated tests. Found a problem? Tell us.