Precision Electrolyte Science
Your sweat is data. We turn it into instructions.
The calculator works now — no account needed. Subscriptions and personalized formulas are coming soon. Join the waitlist.
Sweat Calculator
Enter your pre/post weights and session details. We calculate your exact replacement targets.
Enter your pre and post-session weights to reveal your exact replacement formula.
Your Replacement Formula
Formula Science
Most sports drinks guess. The SweatSciences formula is grounded in published exercise physiology — sodium dominates sweat, potassium maintains cellular voltage, magnesium activates ATP synthesis.
Sodium drives fluid absorption and retention. Potassium maintains the cellular electrical gradient — critical for muscle contraction. Magnesium is the co-factor for 300+ enzymatic reactions including ATP synthesis. In high-heat environments, all three deplete faster and in specific ratios that standard drinks ignore.
Subscription Plans
Calculator works now. Personalized subscriptions are coming. Join the waitlist to be notified when plans launch — and lock in early pricing.
Essential
3-month supply
Optimized
3-month supply + formula calibration
Elite
Custom formula + quarterly recalibration
The Philosophy
"Our goal is for you to eventually not need us — or to upgrade because you got addicted to optimizing. We teach you to read your body. The formula is yours."
Establish your sweat rate. Weigh in before and after every session. Build your personal sweat loss dataset. The calculator becomes your ritual.
Notice patterns. Does heat increase your sodium loss? Does run length change your K:Mg ratio? Your formula begins to personalize. Cramps start to disappear.
You can predict your fluid loss before a session. You know your body's electrolyte signature. You're no longer guessing. That's the whole point.
Community
Generate a QR code for your custom formula. Share it with your studio. Start a hydration challenge.
Your formula QR
Na 220 : K 63 : Mg 16
sweatsciences.com
Upload your Apple Health XML export. Your file is parsed locally — no data leaves your device. Then Sage interprets your HRV, resting heart rate, and weight trends and suggests Na/K/Mg targets based on the science above. This is a starting point, not a diagnostic.
Drop your Apple Health export here
or click to select a file
On iPhone: Health app → Profile photo → Export All Health Data → share the export.xml file here
If you have a .zip file, extract it first and upload export.xml directly.
What These Markers Mean
HRV Drop >10ms
Possible 1.5–2% dehydration. Below 25ms absolute = significant stress marker.
RHR Elevated 3–5 bpm
Each 1% body weight fluid deficit raises RHR approximately 3–5 bpm above baseline.
Weight -1% from Avg
1 lb lost = ~16oz deficit. 2% body weight loss = performance impairment begins.
HSA/FSA Eligible
A physician-signed Letter of Medical Necessity makes electrolyte supplementation HSA and FSA eligible under IRS 213(d). Get yours for $199 — valid 12 months, covers all wellness expenses in your formula.
Get your HSA Letter →