Mulch Calculator
Estimate how much mulch you need for garden beds, borders, circular beds and tree rings. Get cubic yards for bulk delivery, cubic feet, bag count, coverage and optional cost from simple dimensions.
Mulch project
Enter each area, choose its shape and use one target mulch depth for the project.
Advanced settings: existing mulch, waste, bags, weight & cost
How to use, formulas, worked example, FAQs & mulch depth guidance
How to Use the Mulch Calculator
Add each garden bed or landscaped area, choose its shape, enter the dimensions and set the target mulch depth. ToolVault combines multiple areas into one order quantity, then reports cubic yards, cubic feet and bag count. Use Advanced settings when you need to account for existing mulch, waste, bag pricing, bulk pricing or optional weight.
Mulch Calculator Formula
For a rectangular bed, area is length × width. Multiply the area by the mulch depth to get volume:
When depth is entered in inches for an imperial project:
Bag count uses the entered bag volume and rounds upward:
When existing mulch is present, ToolVault calculates the amount still needed to reach the target depth:
An optional purchasing allowance is applied after the geometric volume:
How Many Cubic Yards of Mulch Do I Need?
One cubic yard contains 27 cubic feet. At a 3-inch layer, one cubic yard covers about 108 square feet. This follows directly from the volume formula and is useful for checking a bulk-delivery estimate.
Mulch Calculator for Bags
Retail mulch is sold in different bag sizes, so the calculator asks for the actual bag volume rather than assuming every product uses the same size. A 2 ft³ bag is common, but the bag label should always take priority. Current mulch calculators also emphasize checking the product-specific bag coverage before ordering.
How Deep Should Mulch Be?
Depth depends on the landscape use and material. Penn State Extension describes a 2–3 inch layer for many planted areas, while University of Minnesota Extension describes a 2–4 inch range. Avoid treating one depth as a universal rule; follow the needs of the planting and the mulch product. Penn State Extension guidance and University of Minnesota Extension guidance.
Mulch Coverage Calculator
Coverage depends on depth. At 1 inch, one cubic yard covers about 324 ft²; at 2 inches, about 162 ft²; at 3 inches, about 108 ft²; and at 4 inches, about 81 ft². These values come directly from the cubic-yard volume conversion.
Tree Ring and Circular Bed Calculations
For a circular bed, ToolVault uses the area of a circle. For a tree ring, it subtracts the inner circle from the outer circle, so mulch is not calculated for the trunk-clearance area. Proper mulch placement also means keeping mulch away from tree trunks and plant stems. Penn State tree-mulching guidance.
Worked Example: 20 × 10 ft Bed at 3 Inches
Area = 20 × 10 = 200 ft².
Depth = 3 ÷ 12 = 0.25 ft.
Volume = 200 × 0.25 = 50 ft³.
Cubic yards = 50 ÷ 27 = 1.8519 yd³.
With a 5% allowance, order volume = 1.8519 × 1.05 = 1.9445 yd³.
Using 2 ft³ bags, the calculator rounds 50 × 1.05 ÷ 2 = 27 bags.
How Accurate Is a Mulch Estimate?
The geometric volume is exact for the dimensions entered. Real purchasing quantity can differ because of product size, settling, moisture, uneven ground, irregular bed edges, delivery minimums and how much material remains after installation. Use the supplier's product-specific coverage or bag volume when available.
Frequently Asked Questions
How much mulch covers 100 square feet?
At 3 inches deep, 100 ft² requires about 0.926 cubic yards before waste because one cubic yard covers about 108 ft² at that depth.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 ft³. With 2 ft³ bags, the exact equivalent is 13.5 bags, so a purchase quantity must round up to a whole bag based on the actual volume and allowance.
Can I use the calculator for multiple garden beds?
Yes. Add each bed separately and ToolVault totals them into one order volume.
Can I calculate a tree ring?
Yes. Choose Tree ring and enter the outer and inner diameters. The inner diameter represents the trunk-clearance circle that should remain unmulched.
Can I calculate existing mulch top-up?
Yes. Enter the target depth and the existing settled depth in Advanced settings. The calculator subtracts the existing depth before calculating the additional material needed.
Should mulch touch a tree trunk?
No. Extension guidance recommends keeping mulch away from trunks and stems rather than creating a mound around them. See Penn State tree-mulching guidance.