Objective: The point of this examination was to assess the criticalness of the fetal kidney length (FKL) for the estimation of gestational age. Method: A cross sectional study was carried out on 399 pregnant women with singleton pregnancies having no complications at Baloch Hospital Lalian. Pregnant women with single fetuses underwent standard ultrasound fetal biometry. The fetal kidney length measurements were performed from 20th weeks to 38th weeks of gestation. These measurements were used to date the pregnencies. Results: A positive linear relationship was found between gestational age (measured by femur length) and length of left kidney. G.A in weeks (measured by femur length) = 25.430+1.912 (Left Kidney in cm) with R2=0.939 and p value=0.000<0.05. Another statistically significant positive linear relationship was found between gestational age (measured by femur length) and length of right kidney.G.A in weeks (measured by femur length) =13.496+5.727(Right Kidney in cm) with R2=0.939 and p value=0.000<0.05. Conclusion: FKL is easy to identify and measure. It is most accurate single parameter for estimating GA than other biometric indices especially in cases when the other parameters like BPD, FL, AC and HC are not reliable for assessing GA in the 2nd and 3rd trimester of pregnancy