I think it is important to always get a mix of carbs, fat and protein.

Amounts vary for each person and time. After an extensive cardio workout and an intense weight session would require slightly different ratios.

Just as winter and summer do and times of day and time of month for women.

More cardio likely more carbs, relatively speaking.

If northern European and living in a seasonal climate then likes more protein and fat in winter relatively to individual needs.

Unless testing to get a base line I think the only real ways is to record what you eat and how you feel and keep fine tuning. Even with testing for a base line it is all about awareness of your own body needs and fine tuning for you.

I good sign is recovery and steady energy levels...keep track of mood and energy levels for 3 hours (2.5-3.5 ideally for most) between meals, mood and emotions as well start to give you feed back to what is working for you.

I burn through carbs fast and essentially get a high and low if I don't get enough protein and fat. Other people burn carbs slower and suit a lower protein and fat diet.

I don't think there is a magic number for everyone and we have to start to listen to our own bodies to figure it out..