Mulch Calculator
Square feet × depth in inches ÷ 324 = cubic yards: a 10 × 20 ft bed at 3 in needs 1.85 cubic yards, or 25 bags of 2 cu ft.
Mulch estimator
How to calculate mulch
cubic feet = area (sq ft) × depth (in) ÷ 12 cubic yards = cubic feet ÷ 27 (same as sq ft × depth ÷ 324) bags = cubic feet ÷ bag size (cu ft)
Worked example: a 10 × 20 ft bed is 200 sq ft. At 3 in: 200 × 3 ÷ 12 = 50 cu ft, and 50 ÷ 27 = 1.85 cu yd. In bags that is 25 of 2 cu ft or 17 of 3 cu ft. For round tree rings use the circle option: a ring 8 ft across is about 50 sq ft.
Recommended mulch depth
| Source | Applies to | Depth |
|---|---|---|
| University of Illinois Extension | Mulch in general | 2–4 in |
| University of Illinois Extension | Composted vs coarse mulch | 2–3 in / 3–4 in |
| Iowa State University | Wood chips or shredded bark, well-drained sites (heavy soils 2–3 in) | 3–4 in |
| Penn State Extension | Organic mulch (less on poorly drained soil); fine or double-shredded 1–2 in | 2–4 in |
| UF/IFAS | Established trees, shrubs and beds (1 in around seedlings) | 2–3 in |
| University of Georgia | Mulch ring to the drip line | 2–3 in |
| University of Maryland | Bark and wood chips (pine needles 2–3 in, gravel or stone 1 in) | 1–3 in |
The calculator starts at 3 in, which sits inside every range above (at the top of Maryland's). Topping up an existing bed? Measure what is left and only buy the difference.
Bags per cubic yard
| Bag size | Bags per cu yd | One bag covers at 3 in |
|---|---|---|
| 1.5 cu ft | 18 | 6 sq ft |
| 2 cu ft | 13.5 | 8 sq ft |
| 3 cu ft | 9 | 12 sq ft |
Choosing a mulch
- Pine bark settles slowly: UF/IFAS found it kept two-thirds of its depth after two years.
- Pine straw knits together so it does not wash away, and UGA calls it the lightest to move and handle.
- Rubber mulch: UGA does not recommend it for plants, and UF/IFAS says it is generally less effective than organic mulch at suppressing weeds.
- Cypress mulch: UGA does not recommend it because it may come from trees harvested from wetlands.
- Cocoa hulls: poisonous to dogs (Poison Control).
Frequently asked questions
How much mulch do I need?
Multiply the bed area in square feet by the depth in inches and divide by 324 for cubic yards (the formula UC ANR gives). A 10 × 20 ft bed (200 sq ft) at 3 inches needs 200 × 3 ÷ 324 = 1.85 cubic yards, or 25 bags of 2 cu ft.
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cu ft (Texas A&M AgriLife's figure), 9 bags of 3 cu ft or 18 bags of 1.5 cu ft.
How deep should mulch be?
Most extension services say 2 to 4 inches. Illinois and Penn State give 2 to 4 in, UF/IFAS and Georgia 2 to 3 in, Iowa State 3 to 4 in for wood chips or shredded bark on well-drained sites. Maryland is more cautious at 1 to 3 in. Use less on poorly drained or heavy soil and for fine, double-shredded mulch.
How many square feet does a yard of mulch cover?
At 2 inches a cubic yard covers 162 sq ft, at 3 inches 108 sq ft and at 4 inches 81 sq ft (324 ÷ depth in inches).
How far should mulch be kept from tree trunks?
Keep it off the trunk. Illinois Extension says at least 4 inches away, Iowa State at least 6 inches, and Penn State 3 to 5 inches for young trees and 8 to 10 inches for mature trees.
Is cocoa mulch safe for dogs?
No. Poison Control (the National Capital Poison Center) says cocoa bean mulch contains theobromine and caffeine, like chocolate, which are poisonous to dogs.
Sources
- How Much Compost, Soil or Mulch Do I Need to Purchase?, University of California Agriculture and Natural Resources. Used for: 27 cu ft per cu yd and the sq ft × depth ÷ 324 formula.
- How Much Compost, Soil or Mulch?, Texas A&M AgriLife Extension, Travis County. Used for: 13.5 bags of 2 cu ft per cubic yard.
- Proper Mulching Techniques (Tree Care Basics), University of Illinois Extension. Used for: 2 to 4 in depth; composted 2 to 3 in, coarse 3 to 4 in; 4 in from trunks.
- How deep should the mulch layer be around trees and shrubs?, Iowa State University Extension. Used for: 3 to 4 in wood chips on well-drained sites, 2 to 3 in on heavy soils; 6 in from trunks.
- Mulching Landscape Trees, Penn State Extension. Used for: 2 to 4 in organic mulch; 1 to 2 in fine mulch; trunk clearance.
- Choosing and Installing Mulches, UF/IFAS Gardening Solutions. Used for: 2 to 3 in around established plants; pine bark and rubber mulch notes.
- Mulching in the Landscape (Georgia Green Landscape), University of Georgia Extension. Used for: 2 to 3 in mulch ring; rubber and cypress not recommended; pine straw.
- Mulching Trees and Shrubs, University of Maryland Extension. Used for: 1 to 3 in bark and wood chips; 1 in stone.
- Scotts Nature Scapes Color Enhanced Mulch, ScottsMiracle-Gro. Used for: 1.5 and 2 cu ft bag sizes.
- How Many Tons of River Rock Do You Actually Need, Mulch Mound (landscape supplier). Used for: hardwood mulch 600 to 800 lb per cu yd (typical, supplier figure).
- Cocoa bean mulch can poison dogs, National Capital Poison Center (Poison Control). Used for: cocoa mulch and dogs.
Estimates only. Check local codes and your product's label. Found a number that does not match its source? Send a correction.