Sweat Rate Calculator
Sweat rate tester: personal liters-per-hour from pre/post weigh-ins.
Calculator
Sweat Rate Calculator Results
Sweat rate 1.5 L/h (1.5 L over 1 h) — Heavy sweater.
Sweat-Rate Breakdown
| Measure | Value | Context |
|---|---|---|
| Sweat rate | 1.5 L/h | Heavy sweater |
| Session loss | 1.5 L | 1 kg + 0.5 L |
| Per 20 min | 500 ml | sip cadence |
| Hourly sip | 1,200 ml | ~80% replacement |
| Post need | 2.3 L | 1.5x replacement |
| Verdict | Heavy sweater | sweater type |
Recommendations
- ▸During: sip ~1,200 ml/h; after: 2.3 L with sodium.
- ▸Retest in heat — cool-day rates underestimate races by 30-50%.
- ▸Past 90 minutes, put 500-700 mg sodium in each liter.
- ▸Sweat rate 1.5 L/h (1.5 L over 1 h) — Heavy sweater.
Results
Test Score
85/100
Test completeness
1.5 L/h rate
Liters per hour
1.5 L loss
Total fluid lost
1,200 ml/h sip
During-session dose
2.3 L post
Replacement volume
Heavy sweater
Sweater band
Sweat and sodium math follows ACSM/NATA replacement guidance; weigh-ins and salt-stain observation personalize it.
Visualizations
Sweat gauges
Rate vs 2.5 L/h ceiling
Sweat Score
Formula
The weigh-in equation that personalizes every fluid plan.
Alternative Form
Variables
| Symbol | Name | Unit | Description |
|---|---|---|---|
| L | Lost | kg | Scale delta |
| D | Drunk | L | During session |
| H | Hours | hrs | Duration |
| R | Rate | L/h | Loss / H |
| P | Post need | L | Loss x 1.5 |
Explanation
A kilo lost plus half a liter drunk over an hour is a 1.5 L/h heavy-sweater rate.
Derivation
ACSM/NATA sweat-rate testing protocol.
Step-by-Step Calculation
Follow each step to understand how the result is calculated from your inputs.
Add scale loss and drunk fluid.
Divide by hours.
Band the sweater.
Dose the hourly sip.
Price post replacement.
Confirm the test.
Worked Examples
See how the calculator works with different scenarios.
Scenario
Lost 1 kg, drank 0.5 L, 1 h.
Inputs
Calculation
Rate 1.5/1 = 1.50 L/h
Result
Heavy sweater
Interpretation
Sip ~1.2 L/h; sodium mandatory past the hour.
Understanding Your Result
Your Result: Test Score: 85/100
Typical range: Sweat 0.5-2 L/h; sodium 500-700 mg/L; replace 1.5 L per kilo lost.
What This Means
The output converts weigh-ins into sweat rate, session loss and exact replacement volumes.
Why It Matters
Two percent dehydration measurably impairs output — measured replacement beats generic hourly advice.
Professional Interpretation
Sports dietitians dose fluids from weigh-ins and sodium from sweat saltiness, not from fixed hourly rules.
Rate vs loss
Rate is per hour; loss is the session total. Both come from the same weigh-in.
Water vs sodium
Water volume follows the scale; sodium follows the clock, heat and salt stains.
Recommendations
- •Weigh pre/post monthly
- •Replace 1.5 L per kilo lost
- •Add sodium past 60-90 min
- •Practice race-day logistics in training
Educational Content
Introduction
This calculator turns weigh-ins and session details into exact fluid and sodium numbers.
Concept Explanation
Pre-minus-post plus drunk-minus-urine equals loss; loss times 1.5 equals replacement; sweat liters times saltiness equals sodium.
Applications
Benefits
- •Personal sweat rate
- •Session loss totals
- •Per-hour pacing
- •Replacement volumes
- •Sodium servings
Limitations
- •Single-session snapshot
- •Scale precision needed
- •Saltiness estimated
- •Food sodium ignored
- •Illness unmodeled
Best Practices
- •Weigh nude, towel-dried
- •Test in race-like heat
- •Log every test
- •Retest each season
- •Pair with urine checks
Common Misconceptions
Practical Tips
- •Weigh before/after monthly
- •Towel dry before post-weigh
- •Log heat and kit
- •Salt food normally
- •Beep every 20 min
- •Pale straw confirms
Common Mistakes
Assumptions
This calculator makes the following assumptions to provide estimates:
Limitations
Be aware of these limitations when using this calculator:
Frequently Asked Questions
Answers to common questions about this calculator.
How do I measure my sweat rate?
What is a normal sweat rate?
How much should I drink per hour?
Does running raise sweat rate vs cycling?
Why weigh pre and post?
Can sweat rate be too high?
How does humidity change things?
Should I drink to thirst?
What is the 1.5 L rule?
Do I need electrolytes?
Why salt-stained shirts matter?
Can I just drink when thirsty after?
Related Calculators
Explore more calculators related to this topic.
Related Guides
Deepen your understanding with these educational resources.
Progressive overload, volume landmarks and recovery basics.
Zones, VO2 max and weekly aerobic volume that actually moves fitness.
Protein, calories and hydration to support training and recovery.
Sleep, rest days and deloads that turn training into adaptation.
Glossary
Technical terms used in mortgage calculations explained in plain language.
- Sweat rate
- Liters lost hourly exercising; 0.5-2 L depending on size, heat and effort.
- Weigh-in delta
- Pre minus post session weight — the core personal measure.
- Fluid balance
- Drunk plus retained vs lost; 1.5 L per kilo closes it.
- Per-hour loss
- Total loss divided by session hours.
- Replacement
- Post-session drinking at 150% of the deficit.
- Heat acclimation
- 10-14 days of heat training that raises rate but lowers salt per liter.
- Evaporation
- The cooling part of sweating; humidity blocks it.
- Dehydration
- Body-water deficit; 2% measurably impairs performance.
- Hyponatremia
- Low blood sodium from overdrinking plain water.
- Salt sweater
- Athlete with visibly crusty kit; needs top-end sodium.
- Urine check
- Pale-straw color as a free hydration gauge.
- Rehydration ratio
- Drink ~1.5 L per kilo lost to fully restore balance.
Authoritative References
Trusted sources and standards referenced by this calculator.
Applicable Standards
Was This Calculator Helpful?
Page Information
2026-09-16
2.0.0
Free to use for educational and professional purposes.