Abstract: Background: Knowledge of the weight of the foetus in utero is important for the obstetricians to decide the time and mode of delivery. It can be estimated clinically, biochemically or by radiological imaging .None of the diagnostic tools are direct .Interestingly clinically estimated foetal weight is being found more precise than radiological estimation Aim:. This study was designed to find the error percentage in ultrasound and clinical methods. We also studied the research papers on the role of ultrasound and MRI in the diverse strata of birth weights. Results: The average error in all the weight groups except in >3500 grams group was least with Dares Formula, closely followed by Hadlocks Ultrasound Method. Average error in the >3500 grams group was least with Johnsons formula. For birth weight below 3500 grams clinical estimation by Dares Formula gave the least average absolute error while in birth weights above 3500 grams clinical estimation by Johnson’s Formula gave the least average absolute error. Dares Formula had a tendency to underestimate the foetal weight and had least error in <3500 grams group. Johnsons and Ultrasound method overestimated the foetal weight. Ultrasound methods showed advantage in intrauterine growth restricted and macrosomic babies. MRI is important to detect central fat deposition in babies of diabetic and hypothyroid mothers. Conclusion: The abdominal girth multiplication by symphysiofundal height can be a great concern in developing countries. It is easy and simple and can be used by even by midwives. Ultrasound may be reserved to detect abnormal blood flow in umbilical arteries in growth restricted babies and detecting central fat deposition in clinically macrosomic babies. This would ensure a better use of clinical and diagnostic modalities available to us