Calculator
Rock Tumbler Grit Calculator
Estimate a repeatable starting amount from actual rock-and-media weight and tumbler type, then adjust from your batch notes and manufacturer instructions.
Rock Tumbler Grit Calculator
Estimate a practical starting amount from the actual material load—rock plus reusable media. Manufacturer instructions take priority when they differ.
Weigh the rock and reusable media together before adding water and abrasive.How to use the result
Treat the number as a starting estimate, not a guarantee. Barrel geometry, rock type, abrasive formulation and the manufacturer’s operating instructions can justify a different amount. Record what you used and how the batch behaved so the next run is based on your own evidence.
When not to rely on a calculator
If your tumbler or abrasive manufacturer gives a specific loading instruction, follow it. A calculator cannot diagnose an underfilled barrel, incompatible stones, contamination or a rock surface that is not ready for the next stage.
For the full process, see Rock Tumbler Grit Stages, How Much Grit per Pound? and Start Here.