Mulch Calculator
Cubic yards of mulch and the number of 2 cu ft bags for any bed.
Input sheet
DIY at your own risk. Calcora's calculators and guides are general estimates and information only — not professional, engineering, legal, or safety advice. Always verify local building codes and permit requirements, and hire a licensed pro for electrical, gas, plumbing, structural, or any work you're not fully comfortable doing yourself.
Mulch is one of those jobs where the bagged-versus-bulk decision quietly doubles or halves your cost. This calculator gives you the cubic yards and the bag count so you can see which side of that line your bed falls on.
How it works
Bed length × width × depth in feet, divided by 27. A bag is 2 cu ft, so a yard ≈ 13–14 bags.
Volume is bed length × width × depth in feet, divided by 27 for cubic yards. A standard mulch bag holds 2 cubic feet, so one cubic yard works out to between 13 and 14 bags.
Depth matters more than people think. Two to three inches is plenty for an established bed; three to four inches suppresses weeds in a fresh bed. Going deeper wastes material and can suffocate roots.
Cubic feet = length × width × (depth ÷ 12); cubic yards = cubic feet ÷ 27; bags = cubic feet ÷ 2, rounded up.
Worked examples
A 20 ft × 10 ft flower bed at 3 inches deep. → 25 bags, or about 1.85 cubic yards.
20 × 10 × 0.25 = 50 cu ft. That's 50 ÷ 27 ≈ 1.85 yd, or 50 ÷ 2 = 25 × 2-cu-ft bags.
A 6 ft × 6 ft tree ring at 4 inches deep. → 6 bags.
6 × 6 × 0.333 = 12 cu ft ÷ 2 = 6 bags — well within bag territory.
Tips & gotchas
- Once you pass roughly 2 cubic yards, bulk mulch delivered by the yard is usually cheaper per cubic foot than bags, even with a delivery fee.
- Keep mulch a few inches away from trunks and plant stems — piled-up 'mulch volcanoes' trap moisture and rot the bark.
- Refresh existing beds with a thinner top-up rather than a full depth every year; the old layer is still doing its job underneath.
- Buy a little extra for the inevitable bare spots you'll notice once the bed is mostly covered.
FAQ
How deep should mulch be?
2–3 inches for most beds; 3–4 to suppress weeds. Keep it off trunks and stems.
Bagged or bulk mulch — which is cheaper?
Bagged wins for small jobs because there's no delivery fee and no truck to unload. Bulk pulls ahead past about 2 cubic yards, where the per-cubic-foot price drops enough to beat the bag markup.
How often should I replace mulch?
Top it up once a year to keep a 2–3 inch layer. Organic mulch breaks down and feeds the soil, so you're refreshing the surface, not replacing the whole bed.
Does mulch color fade?
Dyed mulches fade over a season in full sun. Natural shredded hardwood greys gracefully; if color matters, plan to refresh dyed mulch yearly.
Related calculators
Concrete Calculator · Paint Calculator · Flooring Calculator · Gravel & Driveway Calculator · Drywall Sheet Calculator