Sewage sludge produced is either applied to land or used as fertilizer for crops or disposed of in landfills, causing several environmental problems. Recent studies revealed that composting is a proven technology in reducing organic content, heavy metals, and harmful pathogens, improving the nutritional value of sewage sludge, which is useful for crops. But studies on variation in physical properties are rare. Composting physics or physical properties during composting plays a vital role from handling, management, and utilization of end product, i.e., compost. This study mainly deals with the detailed information on physics involved during the degradation process, which is crucial for land and geotechnical applications. In the present study, sewage sludge was used as a composting substrate in 550 L in-vessel rotary drum composter. Emphasis was given in deciphering the changes in physical parameters such as bulk density, porosity, and air-filled porosity and few chemical parameters during the composting process. Besides, a relationship between different physical properties during rotary drum composting was investigated statistically. Bulk density was observed to have increased from 643 to 707 kg m as a result of volume reduction of compost matrix. Moreover, the gravimetric moisture content was found to be less than 45% in the end product, which is recommended for compost.