Home/Tools/Sweat Rate Calculator
Free hydration tool

Sweat Rate &
Hydration.

Weigh yourself before and after a ride, add what you drank, and get your sweat rate per hour plus exactly how much fluid to replace.

Your ride
Results
Sweat rate
33.8 oz/hr
1000 ml/hr
Minimal loss Mild High loss
Total sweat lost 50.7 oz
Body weight lost 1.2%
Drink per hour 30 oz
capped at what the gut can absorb

Results update as you type. Weigh yourself in the same minimal clothing before and after, and empty your bladder before the after weigh-in for an accurate figure.

The maths

How the calculator works

Sweat you cannot see still counts. Any weight you lose on a ride plus every drop you drank came out as sweat, so the two added together is your true fluid loss.

−
Weight lost = weight before minus weight after. One pound equals about 16 fl oz of fluid; one kg equals about one litre.
+
Add what you drank Fluid you drank replaced sweat that already left, so it is added back to get total loss.
÷
Per hour = total fluid loss ÷ ride time in hours. That is your sweat rate.
%
Body weight lost = weight lost ÷ starting weight. Over 2 percent is where performance drops and dehydration sets in.
∎
Drink target Replace most of your sweat rate, capped near 34 oz (1 litre) an hour since the gut can only absorb so much.

Sweat rate is personal and swings with heat, humidity, intensity and body size, so test it on a few different rides. On efforts over 90 minutes or in the heat, replace sodium too with a drink mix rather than plain water.

Want a printable hydration and sweat-test log?
A one-page sweat-test worksheet to track your rate across conditions is coming soon to our shop.
FAQ

Sweat rate and hydration FAQ

Weigh yourself before and after a ride, note how much fluid you drank during it, then add the weight you lost to the fluid you drank and divide by the ride time in hours. One pound of body weight lost equals about 16 ounces of sweat, and one kilogram equals about one litre. This tool does the full conversion for you.

Most cyclists lose between 16 and 34 ounces (about 0.5 to 1.0 litres) per hour, but it varies widely. Big riders working hard in heat can top 50 ounces (1.5 litres) an hour, while an easy ride in cool weather may be under 16 ounces. Your own number is what matters, which is why measuring it beats using an average.

Aim to replace most of what you sweat, up to a practical ceiling of roughly 24 to 34 ounces (0.75 to 1.0 litres) per hour, since the gut can only absorb so much. If your sweat rate is higher than that, accept a small deficit on the ride and rehydrate afterwards rather than forcing down more than you can absorb.

It is the share of your body weight lost as fluid during the ride. Losing more than about 2 percent of your body weight is where performance starts to drop and dehydration becomes a concern. Staying under 2 percent is the practical target for most rides.

Weigh yourself in the same minimal clothing both times, ideally nude and towelled dry, so wet kit does not add phantom weight. Empty your bladder before the after weigh-in as well, since urine produced during the ride is not sweat and would skew the result.

Yes, on longer or hotter rides. Sweat carries sodium and other electrolytes, and replacing fluid alone can dilute what is left. For rides over about 90 minutes or in the heat, use a drink mix with sodium rather than plain water. This calculator estimates fluid, not electrolyte, needs.