Mulch Calculator
Find out how many cubic yards or bags of mulch your beds need. Enter the size and depth of each bed and the estimate updates as you type.
Mulch calculator
Extension services recommend about 2 to 3 in for most beds. Keep it off trunks and stems.
The sizes below are an example. Type over them with your own.
Allowances
Leave blank to use 10%. Covers uneven ground and spillage. Mulch also mats down and breaks down, so you may top it up later.
Cost (optional)
The cost is your price times the rounded amount in the result, plus delivery. Tax and minimum-order charges are not included.
- Area
- 150 sq ft
- Volume
- 37.5 cu ft1.39 cu yd, before the extra
- Extra
- 10%Adds 3.8 cu ft
- Order quantity
- 1.53 cu yd41.3 cu ft
- Bags
- 21 bags2 cu ft bag, rounded up
- Other bag sizes
- 1 cu ft bags: 42, 1.5 cu ft bags: 28
How to use the mulch calculator
- Enter the length and width of each bed in feet and inches. For a round bed, choose Circle. If you already know the square footage, choose Known area.
- Enter the depth you plan to spread, in inches. Use Add another area for separate beds.
- Choose your bag size, or ignore the bag count and order by the cubic yard for bulk mulch.
- Optional: enter the price per bag or per cubic yard and any delivery fee to see an estimated cost.
The calculator does not estimate the weight of mulch. Wood chips, bark, and compost vary too much with moisture and species, so order by volume.
The mulch formula
Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Order = volume × (1 + extra % ÷ 100)
Bags = cubic feet ÷ cubic feet per bag, rounded up
Worked example: a 15 ft by 10 ft bed, 3 inches deep
- Volume: 15 × 10 × 3 ÷ 12 = 37.5 cubic feet.
- Add 10%: 37.5 cubic feet becomes 41.25. Divided by 27, that is 1.5278, shown as 1.53 cubic yards.
- Bags of 2 cubic feet: 41.25 ÷ 2 = 20.63, rounded up to 21 bags.
A round bed. A bed 10 feet across is a circle with a radius of 5 feet. Its area is 3.1416 × 5 × 5 = 78.54 sq ft. At 3 inches deep that is 19.63 cubic feet, or 21.6 with 10% extra. The order is 0.80 cubic yards, or 11 bags of 2 cubic feet.
Check against an extension service. Texas A&M AgriLife Extension works an example of a 10 ft by 10 ft area covered with 3 inches of mulch and gets 0.93 cubic yards. With the extra set to 0, this calculator gives 0.93.
How deep should mulch be?
Mulch holds moisture and slows weeds, but too much of it smothers roots. The University of Georgia notes that a layer 3 inches deep after settling is enough for most plants.
| Where | Depth |
|---|---|
| Around trees and shrubs | 2 to 3 in |
| Around small annuals and perennials | 1 to 2 in |
| Fine or double-shredded mulch | 1 to 2 in |
| Coarse mulch (large particles) | 2 to 4 in |
| Maximum, including old mulch | 4 in |
Source: Virginia Cooperative Extension, publication SPES-661.
| Depth | Cubic feet | Cubic yards | Sq ft per cu yd |
|---|---|---|---|
| 1 in | 8.3 | 0.31 | 324 |
| 2 in | 16.7 | 0.62 | 162 |
| 3 in | 25.0 | 0.93 | 108 |
| 4 in | 33.3 | 1.23 | 81 |
No extra added. The calculator adds 10% by default.
Avoid mulch volcanoes
Pulling mulch up against a trunk is one of the most common landscaping mistakes. UConn Extension and the University of Georgia both warn against it. Virginia Cooperative Extension advises keeping mulch 3 to 4 inches away from the trunk so the root flare stays visible. UConn recommends a mulch ring 2 to 3 feet wide around the trunk, no deeper than 2 to 3 inches.
- Pull old mulch back from the trunk before adding new.
- Spread an even layer and taper it toward the edge.
- To estimate a ring, choose Circle and enter its outer diameter. The trunk itself takes up little area, but keep the mulch off it.
Mulch by the bag or by the yard
Bags are easy to carry and store. Bulk mulch is sold by the cubic yard and delivered by the truckload, which suits large beds. Compare prices on the same basis: the price per cubic yard of bagged mulch is the bag price multiplied by the number of bags in a yard.
| Bag size | Bags per cu yd |
|---|---|
| 1 cu ft | 27 |
| 1.5 cu ft | 18 |
| 2 cu ft | 14 (13.5 rounded up) |
Check the cubic feet printed on the bag, because sizes differ between brands. Enter another size under Bag size if yours is not listed.
Frequently asked questions
How much mulch do I need for 100 square feet?
At 3 inches deep you need 25 cubic feet, which is 0.93 cubic yards or 13 bags of 2 cubic feet. At 2 inches it is 0.62 cubic yards. Those figures have no allowance for settling, and the calculator adds 10% by default.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet: 14 bags if each holds 2 cubic feet (13.5, rounded up), 18 bags of 1.5 cubic feet, or 27 bags of 1 cubic foot. Texas A&M AgriLife Extension gives the same count for 2 cubic foot bags.
How deep should mulch be?
Extension services recommend about 2 to 3 inches around trees and shrubs, and 1 to 2 inches around small plants or when the mulch is finely shredded. Do not let the total, including mulch left from earlier years, build up past 4 inches.
What is a mulch volcano, and why avoid it?
A mulch volcano is mulch piled in a cone against a tree trunk. UConn Extension says mulch piled against the trunk softens the bark and lets insects, fungi, and other organisms in, and that over time this can kill the tree. Spread mulch flat, taper it at the edges, and keep it a few inches away from the trunk.
How often do I need to add mulch?
Organic mulch breaks down, so it needs topping up from time to time. Virginia Cooperative Extension advises replenishing it as it decomposes without letting the layer exceed 4 inches. Measure what is left before you order, and enter only the depth you plan to add.
Sources
- Virginia Cooperative Extension SPES-661: Mulching, purpose, benefits and essential information
- UConn Extension: Mulch volcanoes, a growing problem
- University of Georgia: Avoid mulch "volcano" in landscape
- Texas A&M AgriLife Extension: How much compost, soil or mulch?
- NIST Guide to the SI, Appendix B.8: conversion factors (the yard and the cubic yard)