Health & Training

Sweat Rate & Rehydration Calculator

Measure how much fluid you lose in a session and how much to drink back. A simple before-and-after weigh-in turns guesswork into a number — and it's not a weight-cutting tool.

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Measuring your sweat rate

The method is the one sports scientists use: weigh yourself before and after training, add back any fluid you drank during the session, and the difference is fluid lost to sweat. Divide by session length and you have your sweat rate per hour. Grapplers training in a hot room can lose more than they'd guess, which is why measuring beats estimating.

Replacing what you lose

Following National Athletic Trainers' Association guidance, replace roughly 125–150% of the fluid you lost over the next two to four hours — a bit more than the deficit, because you keep sweating and lose some to urine. For longer or sweatier sessions, include electrolytes (especially sodium), not just water.

This is a recovery tool, not a weight-cut tool. It measures normal training fluid loss so you can rehydrate properly. Deliberately sweating off weight through dehydration is dangerous and hurts performance — that's not what this is for.

Frequently asked questions

How do I calculate my sweat rate?
Weigh yourself before and after a session, add any fluid you drank, and divide the total loss by the time trained. This tool does the math for you.
How much should I drink after training?
Around 125–150% of the fluid you lost, spread over the next few hours, with electrolytes for longer or sweatier sessions.
Can I use this to cut weight?
No. This measures normal sweat loss so you can rehydrate. Cutting weight by dehydration is dangerous and degrades performance — please don't use it that way.