Sweat rate calculator.
Measure how fast you lose fluid when you train. This sweat rate calculator takes your pre- and post-session bodyweight, the fluid you drank, and the session length, then returns your sweat rate per hour and how much to drink to replace it.
Towel off sweat and empty your bladder before the pre-weigh for a clean reading.
Your sweat rate
1.4 L / hour
about 48 fl oz per hour
Drink target per hour
to keep pace with losses
1.4L
Total sweat loss
for this session
1.4L
Bodyweight lost
within the safe range
1.7%
A general guide, not medical advice. Post-session, replace roughly 1.25 to 1.5 L per kg lost and add sodium on long or hot sessions.
the short answer
Sweat rate = (pre-session weight - post-session weight + fluid consumed) / session hours, where 1 kg lost is treated as 1 L of sweat. If you drop 1.4 kg over a 60-minute session and drank nothing, your sweat rate is about 1.4 L per hour. Most people fall between 0.5 and 2.0 L per hour. It is a general guide, not medical advice.
How the sweat rate calculator works.
Bodyweight change across a session is the cleanest way to measure fluid loss, because water is heavy and sweat is close to the density of water. So a kilogram lost during exercise stands in for about a liter of sweat. The only wrinkle is that any fluid you drank mid-session hides part of that loss on the scale, so the calculator adds it back in:
Sweat rate (L/hr) = sweat loss / (minutes / 60)
Bodyweight lost (%) = weight change / pre-session weight x 100
Weight change is your pre-session weight minus your post-session weight. If you enter pounds and fluid ounces, the tool converts to kilograms and liters internally (1 lb = 0.453592 kg, 1 US fl oz = 29.5735 ml) before running the math, and it shows the sweat rate in both liters and US fluid ounces per hour, where 1 liter = 33.814 fl oz.
The bodyweight-lost percentage is the number to watch. Once you are past roughly 2% down, performance and thermoregulation start to slip, so the calculator flags sessions that cross that line. Your sweat rate is not fixed: it climbs in heat and humidity and with harder efforts, so retest across the conditions you actually train and compete in rather than trusting a single reading.
How endurance and hybrid coaches use sweat rate.
For anyone coaching runners, cyclists, triathletes, or hybrid athletes, sweat rate turns hydration from a vague "drink more water" into a concrete plan. You have the client run the test on a couple of representative sessions, then set a drinking target per hour that keeps most efforts inside the 2% window. On long or hot days you layer sodium on top, because at high sweat rates plain water alone dilutes blood sodium instead of being retained.
Doing this across every athlete you coach by hand gets messy fast. A coaching platform stores each client's sweat rate alongside their other data, sets the fluid and sodium target as a trackable habit, and surfaces it next to their check-ins in a branded app, so you can see whether they actually followed the protocol rather than guessing. You spend your time adjusting the plan, not recalculating numbers one athlete at a time.
Turn a sweat rate into a habit every athlete actually follows.
Coachway lets you set hydration, calorie, and macro targets per client, then track them as daily habits and check-ins inside a branded client app - so adherence shows up in the client file instead of being a guess. It is the operating system for online fitness and nutrition coaches, so you stop stitching together calculators, spreadsheets, and chat.
Book a demoSweat rate calculator FAQ.
How does a sweat rate calculator work?
A sweat rate calculator works out how fast you lose fluid during exercise. Weigh yourself before and after a session, note how much you drank during it, and time the session. Sweat loss equals your bodyweight drop plus the fluid you consumed, because 1 kg of bodyweight lost is about 1 liter of sweat. Divide that sweat loss by the session length in hours and you get your sweat rate per hour, plus a fluid replacement target.
What is a normal sweat rate per hour?
Most people lose somewhere between 0.5 and 2.0 liters of sweat per hour during exercise, but the range is wide. Heavy sweaters in hot, humid conditions can exceed 2.5 liters per hour, while a light session in a cool room may sit under 0.5. Because the spread is so large, an individual measurement from this calculator is far more useful than any average, and it can change with heat, fitness, and intensity.
How do I measure my sweat rate accurately?
Weigh yourself nude or in dry minimal clothing right before training, then again immediately after, towelling off sweat first. Use the same scale both times. Track every milliliter you drink during the session, and record the exact duration. Empty your bladder before the pre-weigh so urine does not skew the result. Do the test in the conditions you actually train in, since heat and humidity change sweat rate substantially.
How much fluid should I drink to replace sweat losses?
To stay level during a long session, aim to drink close to your measured sweat rate per hour, sipping steadily rather than gulping. After training, a common guideline is to replace about 1.25 to 1.5 liters of fluid for every kilogram of bodyweight you lost, since some is passed as urine. For sessions over an hour or in the heat, add sodium so the fluid is absorbed and retained rather than simply passed through.
Why does losing more than 2% of bodyweight matter?
Once you are down more than about 2% of your bodyweight in fluid, endurance, strength output, and thermoregulation start to decline, and the effect grows as the deficit deepens. For an 80 kg athlete, 2% is only 1.6 kg. Knowing your sweat rate lets a coach set a drinking plan that keeps most sessions inside that 2% window rather than finding out after performance has already dropped.
Is this sweat rate calculator medical advice?
No. This sweat rate calculator gives a general estimate for healthy adults training in normal conditions and is not medical or clinical advice. Individual fluid and sodium needs shift with medications, heart or kidney conditions, pregnancy, and illness. If any of those apply, or you are planning very long events in extreme heat, check with a doctor or a sports dietitian before setting a hydration protocol.
This calculator is general information, not medical or nutrition advice. Individual fluid and sodium needs vary - if you are pregnant or breastfeeding, have kidney or heart conditions, take medications that affect fluid balance, or are planning very long events in extreme heat, talk to a qualified professional before setting a hydration protocol.
Keep going: set a baseline fluid goal with the water intake calculator, dial in training zones with the heart rate zone calculator, and read the honest guide to electrolytes and hydration.
More free calculators
See all free tools ->Refeed Day Calculator
Refeed-day calorie and carb targets from maintenance, deficit and weeks dieting.
Open calculator ->Cut Length Calculator
How many weeks a cut needs from current and target body fat, with diet-break placement.
Open calculator ->Creatine Dosage Calculator
creatine dosage calculator. Enter your body weight to get a loading-phase dose, a 3 to 5 g daily maintenance d
Open calculator ->Macro Calculator by Body Type
macro calculator by body type: enter your stats, somatotype, and goal for protein, carb, and fat targets tuned
Open calculator ->Coaching Rate Calculator
What to charge per client from your income goal, hours, costs and churn - with the math shown.
Open calculator ->Referral Value Calculator
What one referring client is worth across referral chains, retention and LTV.
Open calculator ->See what Coachway can do for your coaching business
Coachway was built on knowledge from working with 150 online coaches over 6+ years, who all hit the same wall - slow platforms, clunky workflows, wasted hours. Start your 14-day free trial and see what we fixed - the whole platform, no charge today, cancel anytime under Billing.
