It doesn’t take a lot of math to understand machine learning, but you will need some calculus and linear algebra. If you haven’t covered these or it’s been long enough that you need to brush up, there are great free options out there.

The excellent Khan Academy covers Linear Algebra, Differential Calculus, and more. Khan is an incredible resource, but if you are intimidated by calculus or just prefer a methodical pace that allows you to develop intuition about the concepts as you go, I highly recommend Jim Fowler’s Calculus 1 Coursera course.