About Mulch Calculator

This is a free, independent site with tools for people who work on their own yards. A small team of web developers who garden at home runs it. We are not arborists or soil scientists. That is why every depth and weight on the site points to a university extension service or public agency, so you can check it yourself.

Our method

• Area. Rectangles use length x width. Circles use 3.1416 x radius x radius. Tree rings take the inner circle away from the outer one. Triangles use base x height / 2.
• Volume. Area in square feet times depth in feet gives cubic feet. Cubic feet divided by 27 gives cubic yards. A cubic yard is 0.7646 cubic meters.
• Bags. Cubic feet divided by the bag size, rounded up to a whole bag.
• Extra. The extra percent is added to the volume before bags and tons are worked out.
• Weight. Cubic yards times tons per yard. Soil defaults to 1 ton a yard, from Ask Extension. Gravel defaults to 1.85 tons a yard, from the Wisconsin DOT. You can change both.
• Depth advice. From the extension services of Illinois, Iowa State, Cornell, Maryland, Vermont, Florida and California.

Testing

Before each release, automated tests check the math. They confirm that 27 cubic feet make one yard, that 200 square feet at 3 inches is 1.85 yards, that a bag count always rounds up, and that ring and circle areas match hand math.

Limits

The tools give estimates. Real loads vary with moisture, settling and how a supplier measures. Bag labels and supplier weights win over our defaults.

Corrections

Spotted an error? Please tell us on the contact page. We fix confirmed errors quickly and update the date below.

Last updated October 24, 2026.

Before you order. Results are estimates. Bulk material settles, and loads vary by supplier, so check the bag label or ask your supplier for the real volume and weight. Call 811 before you dig. Keep mulch off tree trunks and away from your house foundation, as UC extension advice explains.

References

1. Applying Mulch: Where, When and How Much. UC Marin Master Gardeners, University of California Agriculture and Natural Resources
2. Proper Mulching Techniques (PDF). University of Illinois Extension
3. How deep should the mulch layer be around trees and shrubs? Iowa State University Extension, Yard and Garden
4. Mulch. Cornell University CALS, Turfgrass and Weed ID
5. Mulching Trees and Shrubs. University of Maryland Extension
6. Beware the Mulch Volcano. University of Vermont Extension
7. Principle 4 Guidance: Mulch. Florida-Friendly Landscaping Program, UF/IFAS
8. Soil for raised beds, question #861940. Ask Extension
9. Standard Specifications, Section 305 Dense Graded Base (PDF). Wisconsin Department of Transportation
10. Volume to Weight Conversion Factors (PDF). New Hampshire Department of Environmental Services