It will vary from institution to institution but you can usually expect an interior design bachelors degree to take around 3 years to complete. There will be the option upon having completed the degree and gained some relevant work experience to then go and do a masters in interior design. Interior design masters courses are aimed at those students who wish to achieve a higher level of specialization in this particular discipline. You can generally expect a masters in interior design course to take 1 year to complete if studying full time and 2 years to complete in studying part time.