Young Blonde Girl Posing On The Chair

The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. It specifies things like :
chair back strength of 150 pounds (68 kg)
chair stability if weight is transferred completely to the front or back legs
leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg