Precise measurement of river discharge is a challenging task and at the same time, it is necessary for planning and management of water resources. The stage-discharge curve is a traditional method that is used to identify the flow and requires a river cross-section. Apart from this method, the Acoustic Doppler Current Profiler (ADCP) is also in use by project authorities around the World. Generally, ADCP is used to calibrate the gauge discharge curve but there is less work available when no stage-discharge relationship is available for a section. Therefore, in the present study, a gauge site downstream of the over bridge located on state highway 37 across the river Mej which originates from Bhilwara district, of Rajasthan and joins the Chambal River at Kota district in Rajasthan, is taken where no stage-discharge curve is available. The state water resources department used ADCP to take multiple readings of a velocity profile for the period of 10th August 2021 to 31st October 2021. Thereafter, readings were extrapolated for the full depth of the river section by applying the logarithmic plot method. The curve so derived was validated with the readings of the two automated rain gauge stations in the catchment. The values of the developed rating curve and observed data from the automated water level sensor & automated rain gauge show a good correlation value of 0.86. Therefore, with the use of ADCP readings, a rating curve can be established with the extrapolation equation for the ungauged rivers with fairly good results.