Hydration Status from Urine Calculator

About this calculator

Urine specific gravity (USG) — how dense urine is compared to pure water — rises as the kidneys concentrate urine to conserve water during dehydration, making it a practical proxy for hydration status without a blood draw. This calculation converts USG into estimated urine osmolality, a more clinically standard measure of urine concentration, using the relationship between the two that’s been established in sports-medicine and nephrology research.

Athletes, coaches and sports-medicine staff use urine-based hydration checks because a simple specific-gravity reading (from a refractometer or test strip) is far more practical for daily monitoring than lab osmolality testing, while still tracking closely enough with it to flag under-hydration before a training session or competition. It’s a routine part of weight-category sports like wrestling and combat sports, where rapid dehydration for weigh-ins is a known health risk.

This calculator takes your urine specific gravity and returns the estimated urine osmolality along with your hydration status category.