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💧 Sweat Rate Calculator

Calculate your sweat rate in 30 seconds. The key number to never miss your race hydration again.

Weigh-in protocol

Before exercise Urinate, then weigh yourself in light dry clothing.

During exercise Record precisely the ml of fluid consumed.

After exercise Towel off, weigh yourself in the same conditions.

Result Enter the data below and get your sweat rate.

1. Weigh-in data

Pre-exercise weight (kg)

Post-exercise weight (kg)

Exercise duration (min)

Minimum 30 min for reliable data

Fluid consumed (ml)

Water + sports drinks

2. Conditions

These parameters adjust the replacement factor (70-90%) and personalized recommendations.

Temperature (°C)

Intensity

Results

BPC ALGORITHM

Fill in the weigh-in data then click Calculate.

Sweat rate

ml / hour

Total loss (ml)

% weight lost

Target (ml/h)

0% 1% 2% 3% 4%+

💡 Coach Tip

Race hydration plan

Hourly target --

Every 15 min --

Sips / 15 min --

Bottles / hour (750 ml) --

Understanding your result

🔬 What is the Sweat Rate?

The sweat rate measures the amount of fluid your body loses per hour of exercise. It's the key number for planning your race hydration. Without this data, you drink "by feel" — and feel is a poor advisor when effort lasts more than 2 hours.

⚡ Why it matters in triathlon

A loss of 2% body weight reduces aerobic capacity by 5-10% (Cheuvront & Kenefick, 2014). On an Ironman, that's 10-20 minutes lost. Conversely, drinking too much creates a risk of hyponatremia (blood sodium dilution), potentially serious. The goal is not to replace 100% of your sweat, but to stay in a controlled deficit zone (1-2% loss max).

🌡️ What influences your sweat rate

Temperature & humidity
+30°C = up to 2× more sweat than at 15°C

Intensity
Z4-Z5 increases sweat rate 30-50% vs Z2

Acclimatization
A heat-acclimatized athlete sweats more (but more efficiently)

Genetics & body size
Sweat rate varies from 400 to 2400 ml/h between individuals (Baker, 2017)

🎯 How to use your result

Record your sweat rate — it's your reference number for this condition (temperature + intensity).
Plan your bottles — use the ml/h target from the hydration plan to prepare your fueling.
Repeat the test — take 3-4 measurements in different conditions (hot/cold, bike/run) to build your complete profile.
Adjust on race day — actual heat, stress, and duration change your sweat rate. Use your data as a starting point, not absolute truth.

📊 Typical triathlon benchmarks

Profile	Sweat Rate	Hydration target
Low sweater (cool, Z1-Z2)	400–600 ml/h	300–450 ml/h
Average (20-25°C, Z3)	600–1000 ml/h	500–800 ml/h
Heavy sweater (heat, Z4)	1000–1800 ml/h	800–1200 ml/h
Extreme (Kona, >35°C)	1800–3000+ ml/h	1000–1200 ml/h (capped)