Free sodium calculator

Sweat & sodium calculator

Estimate the fluid and sodium you lose in sweat, and the daily intake that replaces it.

Body weight
lb
Workout duration 60 min
Advanced settings
Workout intensity

Temperature

How salty a sweater are you?

Sources and methodology

Constants published3 referencesFree to embed

This tool estimates sweat volume from body mass, effort and heat, then multiplies it by a sweat sodium concentration. Both steps use published population ranges, listed here in full.

Sweat rate

Baseline 0.78 litres per hour for a 70 kg person at moderate effort in moderate conditions, scaled linearly by body mass.

  • Effort: 0.70 easy, 1.00 steady, 1.45 hard
  • Temperature: 0.82 cold, 1.00 moderate, 1.32 hot
  • Range at 70 kg: 0.45 to 1.49 L per hour

Sweat sodium

A fixed concentration per salty-sweater category, applied to the sweat volume.

  • Low: 600 mg/L (26 mmol/L)
  • Medium: 920 mg/L (40 mmol/L)
  • High: 1,200 mg/L (52 mmol/L)

Sodium lost = sweat litres x concentration. Servings are sodium divided by 800 mg.

Weigh-in mode

Sweat volume = body mass lost during the session plus fluid drunk during it, counting 1 kg lost as 1 litre of sweat.

Sodium uses the same concentration table. Weighing in beats the estimate mode, which infers volume rather than measuring it.

References 3
  1. Baker LB, Barnes KA, Anderson ML, Passe DH, Stofan JR. Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. Journal of Sports Sciences, 2016. Whole-body sweat sodium in 506 athletes.
  2. Baker LB, De Chavez PJD, Ungaro CT, et al. Exercise intensity effects on total sweat electrolyte losses and regional vs whole-body sweat sodium concentration. European Journal of Applied Physiology, 2019. n = 1,303.
  3. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand: exercise and fluid replacement. Medicine & Science in Sports & Exercise, 2007;39(2):377-390.
Limitations, and what this does not tell you 5
  • Individual sweat sodium varies far more widely than three categories can capture, roughly 7 to 100 mmol/L across published samples. Only a lab sweat test measures your own value. This is a population estimate, not a measurement.
  • Roughly one athlete in five is a genuinely salty sweater above 60 mmol/L, which sits above this tool's High setting.
  • It does not predict, prevent or diagnose muscle cramps. Exercise-associated cramping is primarily neuromuscular and is not reliably explained by electrolyte loss.
  • It does not address exercise-associated hyponatremia, which is caused by drinking too much fluid rather than by losing sodium. Drink to thirst.
  • Estimates are for general guidance and are not medical advice.

Constants published here are the values this page computes with. Last reviewed July 2026.

How much sodium do you lose in sweat?

Most people lose 0.5 to 1.5 grams of sodium per liter of sweat, with about 900 mg per liter as a typical average. Two things set your number: how much you sweat, and how salty that sweat is.

  • Per liter of sweat: roughly 500 to 1,500 mg of sodium. Table salt is around 40 percent sodium, so that is about 1.5 to 3.5 grams of salt.
  • Per hard hour: a hot session can pull 1 to 2 liters out of you, so real effort often costs 1 to 2 grams of sodium (about 1,000 to 2,000 mg). A 90-minute session usually runs higher.
  • Salty sweaters: if your shirts dry stiff and white, you sit at the top of every range.

Plain water puts the fluid back but not the sodium, which is why long or hot sessions can leave you cramping and flat even when you drink plenty. The calculator above turns your weight, the conditions, and how salty you run into your own estimate, shown in Saltivate servings.

How much sodium do you actually need?

Most sodium advice is written for the average person, and the average person is not the one reading a sodium calculator.

The familiar numbers, under 2,300mg a day and the American Heart Association's 1,500mg, are aimed at a largely sedentary population eating packaged food, where sodium arrives all day and nobody is measuring it. Those ceilings exist to stop passive overconsumption, and for that job they are sound.

They say very little about you if you are losing salt through your skin. Sweat has to be replaced on top of whatever you eat, and a hard hour in the heat can carry off more than a gram of sodium. That loss is the gap this calculator estimates, and it is why a single daily ceiling is the wrong tool for the question.

So we will not hand you one number for the day. What you need depends on how much you sweat, how salty your sweat is, and what you already eat, and no calculator can see your plate. Use the figure above as what to replenish after you sweat. If you have high blood pressure, kidney disease, or any condition where sodium matters, talk to your healthcare provider about your own needs.

Good to know

Sweat and sodium, answered

How much sodium do you lose in sweat?
Figure roughly a gram of sodium per liter of sweat, so a hard, sweaty hour often costs 1 to 2 grams total. How much you lose overall depends on how long and hard you go and how hot it is. The calculator above estimates it for your own conditions.

How much sodium do you lose in sweat per hour?
At a typical sweat rate of about a liter an hour and roughly a gram of sodium per liter, most people lose around 1 gram of sodium per hour of hard exercise. Heavy or salty sweaters in the heat can lose 1.5 to 2 grams an hour or more.

How much sodium do you lose during 90 minutes of exercise?
A 90-minute session at a steady sweat rate often costs somewhere around 1 to 3 grams of sodium, depending on your size, the heat, and how salty your sweat is.

How much sodium is in a liter of sweat?
Roughly 500 to 1,500 mg of sodium per liter of sweat, with about 900 mg per liter as a typical average. Saltier sweaters land at the high end, which is why two people on the same run can lose very different amounts.

How much salt do you lose when you sweat?
Sodium is part of salt, and table salt is about 40 percent sodium, so 1 gram of sodium is about 2.5 grams of salt. A sweaty hour can mean roughly 2 to 5 grams of salt lost.

Does sodium loss change with heat and intensity?
Yes. Harder effort and hotter, more humid conditions raise both how much you sweat and, for many people, how concentrated that sweat is, so your sodium losses climb on hot, intense days.

Can I use this as a sweat rate calculator?
Yes. The weigh-in mode estimates your sweat rate from your weight before and after a session and what you drank, then turns that into the fluid and sodium you lost, so it works as both a sweat rate and a sodium loss calculator.

How much sodium should you replace after sweating?
A common starting point from the American College of Sports Medicine is roughly 300 to 600 mg of sodium per hour during prolonged exercise, with more for heavy or salty sweaters and on long or hot sessions. One Saltivate serving carries 800mg of sodium. A high-sodium routine is not right for everyone, so check with your doctor about the target that fits you.

How much sodium do I need per hour during a long run, hike, or endurance effort?
Most endurance guidance lands around 500 to 1000mg of sodium per hour of hard sweating, and heavy or salty sweaters sit at the top of that range. One Saltivate serving is 800mg of sodium, which falls right in that window, so roughly a serving per hour of hard effort is a simple way to hit it.

How much sodium do I need a day?
There is no single answer, and the familiar ceilings (under 2,300mg a day, or the American Heart Association's 1,500mg) are aimed at a largely sedentary population where the risk is passive overconsumption. They do not account for what you lose in sweat. If you sweat hard, that loss has to be replaced on top of what you eat. Check with your healthcare provider about your own needs.

Is this a sodium intake calculator?
Not quite. It estimates the sodium you lose in sweat and how much to replenish, rather than setting a daily intake target. A calculator cannot see what you already eat or how your body responds to it, so we do not think it can responsibly hand you a single daily sodium number.

Replenish what you sweat out

800mg sodium, 240mg potassium, and 60mg magnesium per serving. Zero sugar, no stevia, HSA/FSA eligible.

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