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FREE SPORTS SCIENCE TOOL · ACSM · NATA · EAH CONSENSUS · SWEAT RATE TESTED

Sports Hydration
Calculator.

Evidence-based fluid and sodium targets using your measured sweat rate, event duration, and climate conditions. Built on ACSM Position Stand and Third International EAH Consensus guardrails.

ACSM Position Stand 2007
EAH Consensus · NATA · AIS
Pre/Post Sweat Rate Formula
Sodium 300–800 mg/hr · EAH Guardrails

Enter Sweat Test & Event Details

Pre/Post body mass test · Climate · Event · Sodium phenotype

No lab data? Use our default estimates — you can still get an accurate personalised hydration plan. For precision, complete a 45–90 min sweat test on a representative training session.
Sweat Test — Body Mass * Weigh nude (or with consistent dry clothing) before and after a training session. Towel-dry skin post-exercise. Do not use toilet before post-weigh.
Fluids During Test Session * Total volume consumed during the test — not before. 1 standard water bottle = 500 mL = 0.50 L. Enter 0 if you drank nothing.
📌 Enter 0 if you did not urinate during the test session (most common)
Test Session Duration * Duration of the exercise bout between the two weighings. 45–90 minutes is ideal. Shorter sessions have less precision.
🏟️ Event & Performance Details
Sport / Activity Type * Affects sweat rate estimate, fluid access frequency, and sodium defaults. Team sports have intermittent access; endurance events have more structured aid station intervals.
Planned Event Duration * Determines the replacement fraction (f) applied to sweat rate. Longer events require higher replacement to stay within 2% mass loss. Fluid needs are cumulative — totals displayed alongside per-hour targets.
Exercise Intensity * Higher intensity increases sweat rate by 10–20%. If test conditions matched race intensity, select "Same as test". Race pace is typically higher than training pace.
🌡️ Climate & Environment
Event Temperature * Air temperature at the event. Each +5°C above test conditions increases sweat rate ~10–15%. Indian summer competition heat (>35°C) is a severe sweat rate amplifier.
Humidity Level * High humidity impairs evaporative cooling → higher sweat rate. Indian monsoon conditions (high temp + high humidity) are among the most challenging scenarios for athletes.
Clothing & Equipment Burden * Heavy protective gear (football pads, rugby kit) impairs sweat evaporation and increases heat load, raising sweat rate by 10–20% vs shorts and t-shirt.
🧂 Sodium & Electrolyte Profile
Sodium / Sweat Phenotype * Sweat [Na+] varies from 10–90 mmol/L between athletes. Salty sweaters (white crust on skin/kit, stinging sweat) lose far more sodium per litre than average. Lab sweat sodium testing gives the most accurate value.
📌 If you have a lab sweat sodium result, enter it here (typical range 10–90 mmol/L). This overrides the phenotype selection above.
Medical / Risk History * Select all that apply. These activate additional safety guardrails in the calculator output — overdrinking is the primary cause of exercise-associated hyponatremia (EAH).

ACSM 2007 · NATA · EAH Consensus · Sawka et al. · Shirreffs & Sawka · AIS Supplement Framework

FLUID TARGET (ACSM/EAH CALIBRATED)
Complete the form →
SWEAT RATE
— L/h
Adjusted
Na TARGET
— mg/h
Sodium/hour

WHAT YOU GET

ml/hour Fluid TargetACSM-calibrated range with safety guardrails
Sodium mg/hourPhenotype-adjusted · 300–800 mg/hr range
Body Mass Change Prediction0–2% loss target · EAH gain warning
Race Interval Planml per 15/20/30 min aid station
Climate AdjustmentTemperature × humidity × clothing multipliers
EAH Safety GuardrailsEAH Consensus + ACSM Position Stand

WANT MORE?

Get a Race-Day
Hydration Strategy

Our sports dietitian will create a personalised event hydration plan with product recommendations, electrolyte schedule, and pre-race loading protocol.

Book Consultation →

EVIDENCE BASE

ACSM (2007)Exercise and Fluid Replacement Position Stand
EAH Consensus (2015)3rd International Consensus Statement
NATA (2000)Fluid Replacement for Athletes guidelines
Sawka et al.ACSM — individual sweat rate anchoring
AIS (2020)Sports Supplement Framework · Sodium

TRY ALSO

VO₂max + Calorie CalculatorCooper test · ACSM fitness norms
Hypertension Risk (ESH/ESC)BP risk + DASH sodium target
Smart Health CalculatorBMI · TDEE · NIN food groups

⚕️ This tool provides evidence-based hydration estimates — not clinical prescriptions. Individual sweat rates and sodium losses vary widely. For athletes with history of EAH, heat illness, or cardiac/renal conditions, consult a sports physician or accredited sports dietitian before implementing any hydration plan. The EAH Consensus Statement recommends "drink to thirst" as a safe default in mass-participation events. Never drink to the point of weight gain during exercise. Pre/post body mass monitoring is the gold standard for validating any hydration strategy on event day.