What is the difference in the percentage of minoxidil ?

The percentage is just the concentration of minoxidil. 2% and 5% are the only two FDA approved. The higher the concentration above 5% does not mean you will get that much better results.

Topical minoxidil usually comes in 5% strength.  Higher percentages would mean there is more minoxidil concentration.  Higher percentages do not mean it will work better.

It's a common question. Minoxidil is only FDA approved for 2% and 5 %. Not 10%, not 15 %. Not 17.5%. I have seen many, many patients with dizziness, headaches, heart palpitations at the higher doses- and a few who feel extremely unwell. Any use if minoxidil above 5% is an off label use and carries unknown risks. Furthermore, there is absolutely no scientific proof that higher concentrations are consistently better than the FDA approved strengths.