Mulch Calculator
Calculate mulch by the cubic yard and by the bag for garden beds and landscaping. Enter the bed dimensions and mulch depth (2–4 inches is typical) to get total volume and how many 2 cu ft bags that equals. Avoids both under-ordering and the cost of hauling away extra.
Mulch Area Diagram
How the Formula Works
Convert depth to feet
Depth (ft) = Depth (in) ÷ 12 All dimensions must share the same unit before multiplying
Calculate volume in cubic feet
Volume (ft³) = Length (ft) × Width (ft) × Depth (ft) Convert to cubic yards
Volume (yd³) = Volume (ft³) ÷ 27 There are 27 cubic feet in one cubic yard — the standard bulk mulch order unit
Calculate bags required
Bags = ⌈Volume (ft³) ÷ 2⌉ Standard mulch bags hold 2 cubic feet — always round up to whole bags
Frequently Asked Questions
For new garden beds, apply 3–4 inches of mulch. For refreshing existing beds, 1–2 inches is typically enough. A 100 sq ft bed at 3-inch depth requires approximately 0.93 cubic yards or 14 bags of mulch. Enter your exact dimensions above for a precise calculation.
One cubic yard equals 27 cubic feet. Since standard mulch bags hold 2 cubic feet, you need 13.5 bags per cubic yard — so plan on 14 bags per cubic yard. Buying in bulk (by the cubic yard) is almost always cheaper than bags for areas larger than 50 square feet.
Recommended depths: 2–3 inches for established beds and maintenance, 3–4 inches for new beds and weed suppression, 4–6 inches around trees and shrubs. Avoid "mulch volcanoes" — never pile mulch against tree trunks, as this causes rot and pest problems.
Buy in bulk (cubic yards) when you need more than 2–3 cubic yards — it costs 30–50% less than bags and is delivered loose. Choose bagged mulch for small areas, tight access, or precision work. Budget roughly $25–$50/yd³ for bulk and $3–$8 per bag at retail.
Shredded hardwood bark is the most popular all-purpose mulch — it decomposes slowly, resists blowing, and looks clean. Cedar mulch repels insects. Pine straw is excellent for acid-loving plants. Black or dyed mulch provides strong visual contrast but can fade. Rubber mulch lasts longest but does not improve soil.
Organic mulches (wood, bark, straw) decompose and need refreshing every 1–2 years. Check the depth in spring — if it is less than 2 inches, top it off. Do not remove old mulch before adding new; it has become beneficial organic matter. Inorganic mulches (gravel, rubber) rarely need replacement.
A 3-inch mulch layer blocks 90% of annual weeds by preventing seed germination. Going to 4 inches provides even better suppression. Below 2 inches, weeds push through easily. For maximum weed suppression, lay landscape fabric first and add 3–4 inches of mulch on top.
For a circular bed, calculate the area first: Area = π × radius². Then multiply by your desired depth. For example, a 10-foot diameter circle (5-foot radius) has an area of 78.5 sq ft. At 3 inches deep, that is 19.6 cubic feet, or 0.73 cubic yards (about 10 bags).