How to Use the Sweat Loss Calculator
The main reason your weight drops during a workout is fluid lost through sweat. Enter your pre- and post-workout weight along with the fluid you drank during exercise, and this calculator estimates your actual sweat loss, hourly sweat rate, and how much fluid you should drink to recover afterward.
The math is simple: subtract your post-workout weight from your pre-workout weight, then add whatever fluid you drank during exercise — that total is the fluid you actually lost through sweat. A 1 lb weight drop equals roughly 16 fl oz of fluid loss.
The American College of Sports Medicine (ACSM) recommends replacing about 125-150% of your fluid loss. Since you keep losing fluid through urination, drinking only the exact amount lost won't fully rehydrate you. If you feel dizzy or notice signs of severe dehydration, pair fluids with electrolytes and consult a professional if needed. Spreading your rehydration over a few hours instead of chugging it all at once also helps your body absorb it better and eases stomach discomfort.
Frequently Asked Questions
Subtract your post-workout weight from your pre-workout weight, then add the fluid you drank during exercise — that total is your actual sweat loss. A 1 lb weight drop equals roughly 16 fl oz of fluid loss.
The American College of Sports Medicine (ACSM) recommends replacing about 125-150% of your fluid loss. Since you continue losing fluid through urination, drinking only the exact amount lost won't fully rehydrate you.
No. The weight lost right after exercise is mostly water and comes back once you rehydrate. Real body fat changes should be tracked over days or weeks of consistent measurement.