@Inna I set my macros based on Bikman’s protein intake recommendation, which is approx 1.5 gr per kilo of total body weight, with a range of 1.4 - 2. He uses total weight rather than lean mass because it’s a lot easier to measure accurately. My current protein macro is 120 grams, which is 1.8 gr/kg. I went for the higher side of the range because I’m an older male, thin all my life and not wanting to get thinner as I age further by losing lean mass. With the protein macro set, I determined my fat macro this way:
From trial and error I already know how many calories I need to consume to maintain my weight of 145 pounds, which I have done consistently for 3 years. That currently is a range of approx 2500-2900 calories. If I eat below/above that range for more than 3-4 consecutive days I will start to lose/gain weight. The center of that range is 2700 calories, which is my current daily target. I use that number to set my fat and carb macros.
I should mention simply because some folks seem to think I’m advocating CICO, that I use calorie numbers as a measure, not a determinant. I am fully aware of the limitations of CICO and the inherent inaccuracy of calorie numbers. I eat to maintain my weight and use calories as a handy measure only. I do not eat to some arbitrary calorie total in order to maintain, lose or gain. I maintain, lose or gain and have observed how the calorie numbers change doing so.
My current fat macro is 240 grams, that is: 2:1 fat:protein grams; 4.5:1 fat:protein calories. The total of protein and fat calories is 2640 and the difference of 60 calories from my 2700 target is my carb macro, that is: 15 grams. That is an absolute max and I seldom reach it. I generally consume 10 grams or less of carbs daily, as incidental to whatever other good foods I eat.
Please note that this formula based on Bikman’s protein recommendations may or may not apply if you’re much heavier than ‘your normal’. You may need to reduce overall fat intake to increase onboard fat burn. I determined what works for me by trial and error. So you’d have to do so for yourself, but maybe this can help get you started. Hope this helps.