I have been asked this question a number of times and in my experience, there is no one answer that fits everyone. With that said there are some common factors you can consider to determine how often you should wash your hair.
I work out 4 times and this might mean washing my hair more often. If this is the same for you then you might be washing more often as well.
Additionally, I work from home mostly so it is easier for me to wash my hair often and work around my commitments. Another woman with a busier schedule may need more time between washes and will arrange her regiment to suit that need.
If you use heavy thick products you will probably need to wash your hair more often. My eldest daughter uses a lot of oils(affiliate link) which may lead to build up and a wash at least 2-3 weeks at a time.
Your Hair Needs
I deep condition and co-wash my hair every week but I shampoo my hair almost every 4 weeks. I co-wash every week because I noticed that my hair gets really dry and the spritzing every now and then did not work for me.
Instead my hair needs to be drenched in the water to get the moisture back. If your hair retains moisture well then you may decide to co-wash less often.
During summer, at times I would co-wash my hair 2 times a week because it does get really hot and humid where I live and I sweat in my hair.
If I wash my hair in the evening and stretch it by the time I wake up in the morning it would be dry and then I can put it in a bun and be able to go about my day. In the Winter I still wash my hair once but it takes longer to dry so washing less often is more beneficial for me.
If you use these 4 points as your guide then you will know when to wash your hair. Comment below and let us know if this helps.