Urge to urinate begins at what volume of urine in bladder?

The first urge to void is felt at a bladder volume of about 150 mL, and a marked sense of fullness at about 400 mL The suppression of urge after initial experience is a manifestation of the law of Laplace. This law states that the pressure in a spherical viscus is equal to twice the wall tension divided by the radius. In the case of the bladder, the tension increases as the organ fill, but so does the radius. Therefore, the pressure increase is slight until the organ is relatively full. Ref: Ganong &;s review of medical physiology, 23rd edition, page no: 661