How can I calculate how much of our social security is taxable

With the new OBBA I want to prepare for year end and make sure I don't get hit with penalties for not paying enough in my estimated tax payments.  So I need to calculate how much of our social security will be taxable and combine it with other income.  Everything I read says "up to" 50% or "up to" 85% but I can't find the exact number or calculation anywhere.