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Sweat Rate Calculator — Fluid Loss & Hydration Needs During Exercise

Measure sweat loss per hour, dehydration percentage, and recommended fluid intake based on your exercise data

Sweat Rate

52.0 oz/hr

L/hr

1.54

Total Loss

52.0 oz

Dehydration

1.3%

Units

Weigh yourself nude or in minimal dry clothing before and after exercise.

Track all fluids consumed during exercise and any bathroom breaks.

Environmental conditions for reference. Hotter and more humid conditions increase sweat rate.

Your Sweat Rate

52.0
oz per hour
1.54 L/hr
Total Loss
52.0 oz
1.54 L
Dehydration
1.3%
of body weight

Recommended Intake

10.4 oz
every 15 min
308 mL
1,384 mg
sodium/hr
electrolyte target

Aim to replace ~80% of sweat losses. Drink 4–8 oz every 15–20 minutes during exercise.

Fluid Balance

Fluid Intake24.0 oz
Sweat Loss52.0 oz
Deficit: 28.0 oz. Consider drinking more next time.

Typical Sweat Rates

IntensityRange (oz/hr)Range (L/hr)
Low16–240.5–0.7
Moderate24–400.7–1.2
High40–561.2–1.7
Very High56–80+1.7–2.4+

Hydration Tips

Pre-Hydrate: Drink 16–20 oz of water 2–3 hours before exercise and 8 oz 20–30 minutes before.
During Exercise: Aim for 4–8 oz every 15–20 minutes. Use electrolyte drinks for sessions over 60 minutes.
Recovery: Drink 16–24 oz for every pound lost during exercise to fully rehydrate within 2–4 hours.

Example Calculations

160-Minute Moderate Run, 160 lbs

Inputs

Pre-Exercise Weight160 lbs
Post-Exercise Weight158 lbs
Fluid Intake24 oz
Urine Volume4 oz
Duration60 minutes
IntensityModerate

Result

Sweat Rate52.0 oz/hr (1.54 L/hr)
Total Sweat Loss52.0 oz (1.54 L)
Dehydration1.25%
Fluid per 15 min10.4 oz (308 mL)
Sodium per hour1,384 mg

Weight change = (160 – 158) × 16 = 32 oz. Total sweat = 32 + 24 – 4 = 52 oz. Sweat rate = 52 / 1 hr = 52.0 oz/hr = 1.54 L/hr. Dehydration = 2/160 = 1.25%. Recommended intake = 52 × 0.8 / 4 = 10.4 oz per 15 min.

290-Minute High-Intensity Session, 180 lbs

Inputs

Pre-Exercise Weight180 lbs
Post-Exercise Weight176.5 lbs
Fluid Intake40 oz
Urine Volume0 oz
Duration90 minutes
IntensityHigh

Result

Sweat Rate64.0 oz/hr (1.89 L/hr)
Total Sweat Loss96.0 oz (2.84 L)
Dehydration1.94%
Fluid per 15 min12.8 oz (379 mL)
Sodium per hour1,894 mg

Weight change = (180 – 176.5) × 16 = 56 oz. Total sweat = 56 + 40 – 0 = 96 oz. Sweat rate = 96 / 1.5 hr = 64.0 oz/hr = 1.89 L/hr. Dehydration = 3.5/180 = 1.94%. Sodium = 1.89 × 1000 = 1,894 mg/hr.

345-Minute Low-Intensity Walk, 140 lbs

Inputs

Pre-Exercise Weight140 lbs
Post-Exercise Weight139.5 lbs
Fluid Intake12 oz
Urine Volume2 oz
Duration45 minutes
IntensityLow

Result

Sweat Rate24.0 oz/hr (0.71 L/hr)
Total Sweat Loss18.0 oz (0.53 L)
Dehydration0.36%
Fluid per 15 min4.8 oz (142 mL)
Sodium per hour568 mg

Weight change = (140 – 139.5) × 16 = 8 oz. Total sweat = 8 + 12 – 2 = 18 oz. Sweat rate = 18 / 0.75 hr = 24.0 oz/hr = 0.71 L/hr. Dehydration = 0.5/140 = 0.36%. Sodium = 0.71 × 800 = 568 mg/hr.

Frequently Asked Questions

Q

How do you calculate sweat rate during exercise?

Sweat rate is calculated by weighing yourself before and after exercise, then accounting for fluids consumed and urine produced during the session. The formula is: Sweat Rate = (Pre-Weight – Post-Weight + Fluid Intake – Urine Volume) / Exercise Duration. Weigh yourself nude or in minimal dry clothing for the most accurate results.

  • Sweat Rate (oz/hr) = [(Pre – Post) × 16 + Fluid In – Urine] / Hours
  • Average sweat rate: 24–40 oz/hr (0.7–1.2 L/hr) for moderate exercise
  • Elite athletes can sweat 60–80+ oz/hr (1.8–2.4+ L/hr)
  • Sweat rate varies by fitness level, heat acclimatization, and genetics
  • Test in multiple conditions — your rate changes with temperature and humidity
IntensitySweat Rate (oz/hr)Sweat Rate (L/hr)
Low (walking, yoga)16–240.5–0.7
Moderate (jogging)24–400.7–1.2
High (running, HIIT)40–561.2–1.7
Very High (sprinting)56–80+1.7–2.4+
Q

What is a normal sweat rate per hour?

A normal sweat rate ranges from about 0.5 to 2.0 liters per hour (17–68 oz/hr) depending on exercise intensity, temperature, humidity, fitness level, and body size. Most recreational exercisers fall in the 0.7–1.2 L/hr range during moderate activity in temperate conditions.

  • Light exercise in cool weather: 0.3–0.5 L/hr (10–17 oz/hr)
  • Moderate exercise, 70–80°F: 0.7–1.2 L/hr (24–40 oz/hr)
  • Intense exercise, 85–95°F: 1.0–2.0 L/hr (34–68 oz/hr)
  • Heat-acclimatized athletes: up to 2.5–3.0 L/hr in extreme conditions
  • Individual variation can differ by 2–3x between people doing the same activity
ConditionTypical RangeFluid Needed/15 min
Cool (60°F)0.5–0.8 L/hr3–5 oz
Moderate (75°F)0.8–1.2 L/hr5–8 oz
Hot (90°F)1.2–2.0 L/hr8–12 oz
Extreme (100°F+)1.5–3.0 L/hr10–16 oz
Q

How much dehydration is too much during exercise?

Losing more than 2% of your body weight from sweat during exercise impairs performance and increases heat illness risk. A 160-pound person should not lose more than 3.2 pounds during a session. Beyond 3–4% loss, cognitive function declines and the risk of heat stroke rises significantly.

  • 1% loss: minimal performance impact, mild thirst
  • 2% loss: endurance drops 10–20%, increased heart rate
  • 3% loss: strength and power decrease, impaired thermoregulation
  • 4% loss: cognitive decline, nausea, heat exhaustion risk
  • 5%+ loss: dangerous — medical emergency risk, heat stroke possible
Body Weight2% Loss Limit3% Loss Limit
130 lbs2.6 lbs (42 oz)3.9 lbs (62 oz)
160 lbs3.2 lbs (51 oz)4.8 lbs (77 oz)
190 lbs3.8 lbs (61 oz)5.7 lbs (91 oz)
220 lbs4.4 lbs (70 oz)6.6 lbs (106 oz)
Q

How much sodium do you lose in sweat?

Average sweat sodium concentration ranges from 200 to 1,600 mg per liter, with most people losing 800–1,000 mg/L. A person sweating 1 L/hr typically loses 800–1,000 mg of sodium per hour. Heavy sweaters with salty sweat (white residue on clothing) may lose 1,200–1,600 mg/L.

  • Average sodium loss: 800–1,000 mg per liter of sweat
  • Light sweater: 400–600 mg sodium per hour
  • Moderate sweater: 700–1,200 mg sodium per hour
  • Heavy/salty sweater: 1,200–2,000+ mg sodium per hour
  • Sports drinks typically contain 300–500 mg sodium per 16 oz serving
Sweater TypeSodium (mg/L)At 1 L/hr Loss
Low sodium200–500200–500 mg/hr
Average500–1,000500–1,000 mg/hr
Salty sweater1,000–1,4001,000–1,400 mg/hr
Very salty1,400–1,600+1,400–1,600+ mg/hr
Q

How much fluid should I drink during exercise?

The general guideline is to drink 4–8 ounces every 15–20 minutes during exercise, but the ideal amount depends on your individual sweat rate. Aim to replace about 80% of sweat losses — complete replacement during exercise is not necessary and can cause hyponatremia (overhydration).

  • Pre-exercise: 16–20 oz, 2–3 hours before; 8 oz, 20–30 min before
  • During: 4–8 oz every 15–20 min (adjust to your sweat rate)
  • After: 16–24 oz for every pound lost during exercise
  • Use electrolyte drinks for sessions longer than 60 minutes
  • Never drink more than your sweat rate — overhydration is dangerous
TimingAmountPurpose
2–3 hrs before16–20 oz waterStart hydrated
20–30 min before8 oz waterTop off fluids
Every 15–20 min4–8 ozReplace sweat losses
Post-exercise16–24 oz/lb lostFull rehydration

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Last Updated: Mar 9, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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