Sweat Loss Calculator
Sweat loss total: session fluid deficit from weigh-ins with replacement plan.
Calculator
Sweat Loss Calculator Results
Loss 1.5 L (1.4% of body weight); replace 2.3 L — Dehydrated — restore.
Sweat-Loss Breakdown
| Measure | Value | Context |
|---|---|---|
| Session loss | 1.5 L | pre - post + drunk |
| Body-weight % | 1.4 % | dehydration depth |
| Scale delta | 1 kg | pre/post weigh-in |
| Replacement | 2.3 L | 1.5x within 4 h |
| Hourly next time | 1,200 ml | ~80% guide |
| Verdict | Dehydrated — restore | session read |
Recommendations
- ▸Replace 2.3 L steadily with sodium-containing fluids.
- ▸Next session, sip ~1,200 ml per hour from the start.
- ▸Pale-straw urine within 4 hours confirms restoration.
- ▸Loss 1.5 L (1.4% of body weight); replace 2.3 L — Dehydrated — restore.
Results
Session Score
70/100
Hydration management rating
1.5 L loss
Liters lost
1.4% down
Dehydration depth
2.3 L replace
Recovery volume
1,200 ml/h next
Hourly guide
Dehydrated — restore
Session read
Sweat and sodium math follows ACSM/NATA replacement guidance; weigh-ins and salt-stain observation personalize it.
Visualizations
Loss gauges
Dehydration depth
Sweat Score
Formula
Weigh-in loss totals with dehydration-depth scoring.
Alternative Form
Variables
| Symbol | Name | Unit | Description |
|---|---|---|---|
| A | Pre | kg | Before session |
| B | Post | kg | Towel-dried after |
| D | Drunk | L | During session |
| L | Loss | L | (A-B) + D |
| P | Depth | % | Delta / A x 100 |
Explanation
A kilo delta plus half a liter drunk is 1.5 L lost — 1.4% down, replace 2.25 L.
Derivation
ACSM/NATA weigh-in protocol.
Step-by-Step Calculation
Follow each step to understand how the result is calculated from your inputs.
Subtract post from pre.
Add drunk fluid.
Express as body percent.
Price replacement.
Set next-time hourly.
Score the session.
Worked Examples
See how the calculator works with different scenarios.
Scenario
70 to 69 kg, 0.5 L drunk.
Inputs
Calculation
Loss 1.5 L, depth 1.4%
Result
Restore 2.25 L, score 70
Interpretation
Schedule sipping, not chugging.
Understanding Your Result
Your Result: Session Score: 70/100
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?
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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
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Page Information
2026-09-16
2.0.0
Free to use for educational and professional purposes.