About Gravel Calc Pro

Gravel Calc Pro is a free, independent set of calculators for gravel, pea gravel, river rock, decorative rock and crushed stone. A small team of web developers and home project builders runs it. We do not sell stone, and no supplier pays us.

How we calculate

Every page uses the same steps. First we find the area of your shape. Then we multiply by the depth to get cubic feet and divide by 27 for cubic yards. The 27 comes from NIST Handbook 44. Tons are cubic yards times the weight per yard. Bags are cubic feet divided by the bag size, rounded up to whole bags.

A set of automated tests checks the math before each release. The tests check each shape, unit changes, bag rounding, waste and cost. They also check that our numbers fall inside the University of California rule that a ton of gravel covers 80 to 120 square feet at 2 inches.

Where the weights come from

Stone weight is the one number that changes the most. We only use weights published by a producer or printed on a bag label. Each one is listed below with its source. Rock from your local quarry may weigh more or less, so the tool lets you type your own number.

Updates

Last updated October 22, 2026. Found a mistake? Please tell us.

References

  1. NIST Handbook 44, Appendix C: General Tables of Units of Measurement
  2. Calculating Cubic Yards vs. Tons, Gorham Sand & Gravel
  3. Tonnage Calculator conversion factors, Kokosing Materials
  4. QUIKRETE Hardscapes Pea Pebbles specifications (Ritter Lumber listing)
  5. Vigoro 0.5 cu. ft. Bagged River Pebble specifications, The Home Depot
  6. Hardscapes stones and pebbles, QUIKRETE
  7. Gravel Pathways in the Garden, UC Master Gardeners, University of California ANR
  8. Stone (Crushed), Mineral Commodity Summaries 2025, U.S. Geological Survey
  9. Gravel Roads Maintenance and Design Manual, SD LTAP for FHWA (hosted by U.S. EPA)