SweatSciences
Free sweat calculator — your formula, not the average

Know exactly what to drink.

A hot 90-minute class can cost a salty sweater 2,500+ mg of sodium — and a standard sports drink puts back only about 330. Sweat sodium varies tenfold between people — your formula is not the label. Get yours free in 60 seconds.

The math nobody shows you

Standard products give everyone the same dose. Sweat sodium ranges 200–2,000 mg/L between people — a tenfold spread. Here is what the numbers actually look like.

Athlete / session Sweat rate Na loss/hr Sports drink gives The gap
Light runner, cool day, 60 min 0.7 L/hr 560 mg ~330 mg 230 mg short
Average cyclist, 90 min moderate 1.1 L/hr 1,210 mg ~330 mg 880 mg short
Hot yoga, 107°F, 73 min 1.7 L/hr 1,870 mg ~330 mg 1,540 mg short
Salty sweater, summer trail race, 2 hr 2.1 L/hr 3,780 mg ~330 mg 3,450 mg short

Na loss = sweat rate × sodium concentration (800–1,800 mg/L range). Standard sports drink: 1 serving ~330 mg Na. Sources: GSSI, PMID 33895027.

Duration 60 min
20 min3 hours
Heat / effort
Your sweat
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Sodium
mg
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Potassium
mg
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Magnesium
mg
Your mix — tap − + to dial in each ingredient
My sessions →
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Educational estimate — not medical advice. If you have cardiac or kidney conditions, high blood pressure, or are pregnant, consult a sports medicine physician before changing your sodium intake.

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1 serving
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No magic powder. Just the right amounts.

Off-the-shelf tabs give everyone the same dose — but sweat sodium varies 200–2,000 mg/L between people.i We don't manufacture anything. We do the math and point you at proven products.

01 · Measure

Your number, free

The calculator turns your workout into your exact sodium, potassium and magnesium target. No account, no catch.

02 · Build

Real food + minerals

A real-food base (Skratch) for flavor and carbs, topped up with bulk pink salt, potassium and magnesium. Each button links straight to Amazon.

03 · Save

About $2 a session

Your dose, your cost — roughly $1.50–2 versus $6.50 for pre-mixed tabs. Most people save $700+ a year.

Homemade recipe
Make your own, dosed to you
The real recipe — and how LMNT, Liquid I.V., Nuun and Gatorade actually compare, milligram by milligram from their own labels.
See the recipe →
Hot yoga
You sweat like an athlete
A hot class costs endurance-race sodium in a room that feels like rest — up to 1,870 mg, replaced ~7% by a sports drink. What to actually put back.
Hot yoga hydration →
The build guide
Fire your $200 sweat test
Labs charge $130–200 for your number and tabs run $6 a session. The whole stack — free number, ~$2 mix, a weekly AI review — in six moves.
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Caffeine, creatine, bicarbonate, beta-alanine, beetroot — the five supplements with real evidence, ranked for your sport and goal.
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The science
Why salt, not just water
Your brain has a salt sensor (the OVLT). Water alone won't reset it. The primary-source physiology, in plain language.
Read the science →
For runners
Distance & metabolism
Race-week hydration and metabolic science of endurance — written with a Class of 2026 distance athlete. 4:19 mile. 15:40 5k.
See /distance →