Sweat rate and workout hydration calculator

Sweat rate and workout hydration calculator: what it is for

By weighing yourself before and after a workout, you can find out how much fluid you lose per hour: the weight difference plus what you drank, minus urine, divided by the length of the session. The calculator shows your sweat rate, the percentage of body weight lost (above 2% usually hurts performance), how much to drink every 15 minutes and how much to replace afterwards, 1.25 to 1.5 times what you lost.

Everything is calculated in your browser: no health data is sent or stored on a server.

How to use

1. Weigh yourself without clothes before and after the workout.
2. Enter what you drank, any urine and the duration.
3. See your sweat rate and hydration plan.

When to use it

• Planning hydration for a marathon or long race.
• Cycling and running workouts in the heat.
• Team sports and gym athletes.

Frequently asked questions

How do I measure my sweat rate?

Weigh yourself without clothes before the workout and again right after, drying off the sweat. The weight difference, plus what you drank and minus any urine, is the fluid you lost: 1 lb is about 16 fl oz. Dividing by the length of the workout gives your sweat rate per hour.

How much dehydration is too much?

Losses above about 2% of body weight usually start to hurt performance in endurance exercise, especially in the heat. The goal of drinking during the workout is to stay below that mark.

How much should I drink after a workout?

A common guideline is to replace about 1.25 to 1.5 times the fluid lost (roughly 20 to 24 fl oz for every pound lost) over the next few hours, because part of it is lost through urine. In long workouts, drinks with sodium help you hold on to the fluid.

Is it really free?

Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.

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