Aim To study the renal length in various age groups and to find out its correlation with femur length and other anthropometric measurements.

Subjects and methods A prospective study in a tertiary care children’s hospital from March 2003–February 2004. 231 normal children between days 1–18 years of age were studied. All children had their anthropometry (height/length, weight, head circumference) and femur length checked by a single observer using standard measures and also had an ultrasonogram of the abdomen to measure kidney length by a single radiologist using an L & T Sapphire model, 5 MHz mechanical sector probe.

Results Male:female ratio = 1.5:1. The mean renal and femoral length were 7.3 and 23.5 respectively. In univariate linear regression analysis, we observed that for every unit increase in femur length the kidney length increased by 0.13 cm and we derived the following formula: kidney length  = 4.2+0.13× femur length

Also, for every unit increase in height the kidney length increased by 0.04 cm and the formula is: kidney length = 3.1+0.04× height.

Conclusion Femur length correlates well with renal length. It will be useful in bedside monitoring of children with chronic renal disorders.