This paper describes a method to deduce in situ soil density from ripping and raking force measurements. A clear understanding of the properties of the substrate - including density - is required for effective preparation of any site, whether on Earth, the Moon, or Mars. When the substrate is soil or regolith, the density often must be modified through compaction to meet stability requirements. Scaled experiments conducted with JSC-1A lunar regolith simulant form the basis for a potentially useful relation between soil or regolith density and ripping force, ripper tine spacing, and number of tines. The high data acquisition rates of modern instrumentation thus permit high-resolution density mapping of any site being subjected to ripping or raking. This would be valuable for scientific study. It also would provide calibration in situ for some aspects of remote sensing.