How many castors should a chair have for stability?

A chair should have at least four castors for optimal stability, especially in a laboratory or healthcare setting where safety is a priority. This design helps distribute the weight of the chair evenly across its base, reducing the risk of tipping over when the user is seated and shifting their weight. Additionally, a base with four castors provides better mobility while maintaining a stable position when the chair is not in motion, which is essential in environments where users may need to adjust frequently or transfer quickly between tasks. In contrast, chairs with fewer than four castors may compromise stability and safety, increasing the risk of accidents or falls.