Mulch Calculator
Enter your bed size and how deep you want the mulch to find cubic yards for bulk delivery — or bags for small jobs.
Runs entirely in your browser — your numbers never leave this page.
How it works
Mulch is sold by the cubic yard (bulk) or the bag (usually 2 cubic feet). The math:
Volume (cu ft) = Length × Width × (Depth ÷ 12)
Cubic yards = Volume ÷ 27
- 3 inches is the standard depth — enough to suppress weeds and hold moisture without suffocating roots.
- Coverage rule: 1 cubic yard covers ~108 sq ft at 3 in, ~81 sq ft at 4 in.
- Bags vs bulk: bags cost 2–3× more per yard. Above ~2 cubic yards, bulk delivery wins.
- Mulch volcanoes kill trees — keep mulch 2–3 inches back from trunks and stems, never piled against bark.
- Re-mulch yearly: mulch decomposes, which is the point — it feeds the soil as it breaks down.
Frequently asked questions
How much mulch do I need?
Multiply bed area by depth: a 20×4 ft bed at 3 inches needs 20 cubic feet, or about 0.75 cubic yards. Add 10% for settling.
How deep should mulch be?
3 inches is the standard. 2 inches works as a yearly top-up; 4 inches for aggressive weed suppression. Deeper than 4 inches can suffocate roots.
How many bags of mulch are in a cubic yard?
About 13.5 two-cubic-foot bags make one cubic yard (27 ÷ 2). Buy bulk above ~2 yards — it is far cheaper.
Should I put landscape fabric under mulch?
Usually no — fabric blocks the mulch from feeding the soil as it decomposes, and weeds root through it anyway. Thick mulch alone suppresses weeds better long-term.
What is the difference between bark, wood chips, and shredded mulch?
Shredded bark knits together and stays put on slopes; nuggets look tidy but float away in rain; wood chips are cheapest and great for paths. All feed soil as they break down.
How often should I re-mulch?
Yearly — top up 1–2 inches each spring. Mulch decomposes by design; disappearing mulch means it is working.
Can mulch attract termites?
Termites eat any wood in soil contact, but studies show mulch against a foundation is a minor risk compared to wood-to-house contact. Keep mulch 6+ inches below siding and away from direct wood contact.
Is dyed mulch safe?
Most dyed mulches use carbon or iron-oxide colorants considered safe, but cheap dyed mulch can hide ground-up pallet wood. For vegetable beds, use undyed natural mulch.
How do I measure an irregular bed?
Break it into rectangles and add them up, or walk the perimeter and estimate average length × average width. Round up — mulch is cheap, second trips are not.
Can I mulch in fall?
Yes — fall mulching insulates roots over winter. Just keep it off plant crowns so winter moisture does not rot them.