My daughter is 16months and she weight 8.5 kg is she in normal weight?

Weight: A lot depends on her birth weight. Normally a child will triple its birth weight at a year and in the second year of life will gain 2-5 pounds. At 8.5 kg she would be low normal in weight

Weight for age: Your daughter is around the 10th percentile. To decide if her weight is "normal" it is also helpful to know what percentile she has been on at her previous well checks. Dropping off a higher percentile can be a sign of caloric or nutritional deficiency.

Review her velocity: of growth in length, weight & head circumference-for-age from birth with her pediatrician. Also review her weight-for-length. If her growth curves are proportional, that's fine. If her weight-for-length has been < 5th %ile, her doctor may evaluate for causes of pediatric undernutrition. For reassurance, use developmental screens & M-CHAT on firstsigns.org & share the results with her pediatrician.

Lower weight: this weight is lower than usual, still may be normal if she is growing steadily and consistently. Please discuss with your pediatrician

Weight: Thats about 18 lbs and that is a little on the smaller side, BUT that might be perfectly fine for her. If she's following her own growth curves, then thats fine. If she has been dropping on the growth curve, then either she's not getting enough calories or something else can be going on.