The correct answer depends on which kind of toothbrush you use!
From our friends at Oral B: https://oralb.com/en-us/oral-health/why-oral-b/electric-toothbrushes/when-to-change-toothbrush-or-head
From our friends at Colgate: https://www.colgate.com/en-us/oral-health/basics/brushing-and-flossing/how-often-should-you-change-your-toothbrush-0114
From our friends at Sonicare: https://www.usa.philips.com/c-f/XC000006600/how-often-should-i-replace-my-philips-sonicare-brush-head
