In 2020, the premium is $144.60.
According to http://faq.ssa.gov/ : “Some people who collect Social Security benefits and have their Part B premiums deducted from their payment will pay less. This is because their Part B premium increased more than the cost-of-living increase for 2020 Social Security benefits. Social Security will send a letter to all people who collect Social Security benefits (and those who pay higher premiums because of their income) that states each person’s exact Part B premium amount for 2020.”