Garden

Mulch Calculator

Spring landscaping starts with mulch — either bagged from the big-box ($4-6 per 2-cu-ft bag) or bulk delivered ($30-50 per cubic yard) for larger jobs. Pricing crossover happens around 10 bags (1 cubic yard); above that, bulk is dramatically cheaper. This calculator handles rectangular beds and circular tree rings. Pick shape, enter dimensions, set mulch depth (2-3 inches for established beds, 3-4 for new beds or weed suppression), get cubic yards and bag count. Don't go deeper than 4 inches — too much mulch suffocates roots and creates volcano-mulch tree damage.

Enter your bed dimensions and depth.

Mulch types compared

Hardwood mulch (oak, maple): $4-6 per 2-cu-ft bag, $30-50 per yard bulk. Lasts 1 season, fades to gray in 3-4 months. Improves soil as it decomposes.
Cedar mulch: $5-8 per bag. Natural insect repellent. Lasts longer than hardwood, distinctive smell.
Pine bark: $4-6 per bag. Acidic; good for azaleas, blueberries, rhododendrons.
Cypress mulch: $5-7 per bag. Insect-resistant. Some environmental concerns about over-harvesting.
Dyed mulch (red, brown, black): $4-6 per bag. Color lasts 2-3 seasons. Dye is vegetable-based but some people avoid it.
Rubber mulch: $8-12 per bag. Permanent, doesn't decompose. Concerns about heavy metal leaching in some applications.
Stone / rock mulch: $20-100+ per yard bulk. Permanent, low-maintenance, no organic matter benefit. Hot in sun.
Living mulch (cover crops, clover): seeded. Free except seed cost. Annual replanting.

The math behind the bags

Cubic feet = area (sq ft) × depth (feet). For a 3-inch depth: depth = 3/12 = 0.25 ft.

Worked example: 20 ft x 6 ft bed at 3" depth. Area = 120 sq ft. Volume = 120 × 0.25 = 30 cu ft. In 2-cu-ft bags = 15 bags. As cubic yards = 30/27 = 1.11 yards. Either: 15 bags at $5 each = $75; or 1.5 yards bulk delivered at $40/yard = $60 + delivery. Around the threshold; either works.

How to use this calculator

Pick shape: rectangle or circle.
Dimensions in feet: length × width, or radius for circles.
Depth in inches: 2-3 for refresh, 3-4 for new beds, max 4.
Output: cubic yards, 2-cu-ft bag count, coverage area.
For multiple beds: calculate each, sum totals.

Common scenarios

Refreshing 200 sq ft of landscape beds at 2" depth. Volume: 33 cu ft = 17 bags or 1.2 yards. Bag math wins: $85 in bags vs $50+ delivery for 1.5 yards.

New tree ring, 8-ft diameter, 4" depth. Area = 50 sq ft. Volume = 16.7 cu ft = 9 bags or 0.6 yards. Bags win here; 9 bags fit in a sedan trunk.

Whole-yard mulch refresh, 800 sq ft total at 3". Volume = 200 cu ft = 100 bags or 7.4 yards. Bulk delivery wins big at this scale — 7.5 yards at $40/yard = $300 + delivery vs $500-700 in bags + the trip cost.

FAQ

How deep should mulch be? +

2-3" for established beds. 3-4" for new beds or where you want serious weed suppression. Deeper than 4" can suffocate plant roots and trap moisture against tree trunks, leading to rot. "Volcano mulch" around tree trunks (a high mound) is a common mistake — keep mulch 2-3" away from the trunk itself.

Bulk vs bags — when to choose which? +

Crossover around 10-15 bags (1 cubic yard). Below that: bags are easier (no shovel, no driveway pile). Above: bulk is dramatically cheaper per cubic foot and one truck delivery is faster than 15+ bag trips.

How long does mulch last? +

Hardwood/pine bark: 1-2 seasons before significant decomposition. Color fades to gray in 3-4 months even on quality mulch. Cedar: 2-3 seasons. Cypress: 2-3 seasons. Rubber: indefinitely. Rock: indefinitely. Most homeowners refresh 1-2 inches of new mulch each spring on top of existing material.

Should I remove old mulch? +

For natural wood mulches: no — it's decomposing into soil, just add new on top. For rubber, dyed, or unwanted mulch types: yes, remove before adding different material. Tilling old wood mulch into soil works well; rubber/stone don't decompose.

Does mulch help with weeds? +

Yes — mulch blocks light to weed seeds in the soil and creates a physical barrier. 3-4" depth gives best weed suppression. Combine with weed-suppressing landscape fabric underneath for extra effectiveness (though fabric eventually clogs and degrades soil over years).

Should I dye my mulch? +

Dyed mulches use iron oxide (red, brown) or carbon black colorants. Generally safe; some people prefer natural. Dye holds color 2-3x longer than natural wood (which fades to gray in months). Whether to use is mostly aesthetic preference.

Is mulch good for the soil? +

Organic mulches (hardwood, cedar, pine, cypress) decompose over time and feed soil with organic matter — improves soil structure and biological activity. Inorganic mulches (rubber, rock) don't add organic matter; rock can actually warm soil and create unfavorable conditions for some plants.

What's pet-friendly mulch? +

Cedar (cats and dogs may chew but it's safe). Avoid cocoa bean mulch (chocolate compound is toxic to dogs). Pine straw is generally safe. Rubber mulch — not toxic but pets can swallow pieces. For yards with pets, natural cedar or hardwood is the safe choice.

How do I deal with wood mulch and termites? +

Wood mulches don't attract termites by themselves, but a 4+ inch mulch bed touching your home's siding gives termites a moist runway from soil to wood frame. Keep mulch 6 inches away from foundation/siding. Cedar and cypress are mildly termite-resistant; pine bark is neutral. If you have a known termite history, use rock mulch in the 18-inch perimeter band against the house and wood mulch elsewhere.

Is bulk mulch from a tree service safe to use? +

Free or cheap chipped mulch from arborists is great for general bedding, paths, and around mature trees. Two cautions: (1) avoid using fresh wood chips around tender annuals or vegetable beds — the chips can temporarily tie up nitrogen as they decompose; let them age 6+ months first. (2) Confirm none of the chipped material was diseased (verticillium wilt, black walnut allelopathy, etc.) before piling it near sensitive plants.