If you only use it to browse facebook, youtube, i would say the 100%-90% over a year. But if you spend two hours on gaming daily, 11% in a period of 8 months. Also depends on which model you have. Me and my friend purchased iPhone X at the same time and we played games togethers.
His model# A1865 that uses Qualcomm chip conserves energy better, still has 96% battery left.
My iphone X model# A1901 has 89% battery left, i don't play as much game as he does.