A 50 mL volumetric flask is calibrated to the 0.01 mL and will hold exactly 50.00 mL when filled to calibration line.
Every volumetric flask is calibrated with 0.01 mL so that when the liquid is filled till the calibration line the flask should hold 50.00 mL fluid in it. It gives precise and accurate measurements for the experiments. Calibration is a must for every glassware which ensures less experimental errors.