Sustainable Development Goal 6.2 measures sanitation progress by type of toilet service. Improving people’s subjective sanitation experiences is also important but rarely rigorously measured. The Sanitation-related Quality of Life index (SanQoL-5) combines answers to five simple questions (disgust, privacy, disease risk, shame and safety) into an overall score ranging from 0 to 1. Here we evaluated the validity and reliability of SanQoL-5 by interviewing 6,165 people across rural and urban areas of six countries: Ethiopia, India, Kenya, Malawi, Mozambique and Zambia. We found good evidence for construct validity, with support (P < 0.05) for 87% of hypothesized associations between SanQoL-5 and toilet quality characteristics. In 75 intercountry comparisons, only 9% of instances showed evidence of meaningful differential item functioning, suggesting good cross-cultural comparability. SanQoL-5 conformed to expectations in item response theory models, and we found evidence of convergent, discriminant and known groups validity. SanQoL-5 can be used in impact evaluation, monitoring, needs assessment and benefit–cost analysis.