1. Multiple each macronutrient by the number of calories per gram:
Fat 10gms*9 calories/gm= 90 calories,
Protein- 18gms*4 calories/gm= 72 calories
Carbohyrates= 25 gm*4 calories/gm= 100 calories
2. Add all the calories of macronutrients= 90+72+100= 262 calories
3. Divide each calorie from total number of calories in the diet
Fat= 90/280= 0.32 or 32%,
Proteins- 72/280 -0.258 or 25.8%,
Carb-100/280- 35.8%