Dehydration Percentage Calculator
Body-weight loss as dehydration percent with the performance and medical bands at each level.
Acute weight drops over hours are essentially all water — the 2% line is where cognition and endurance measurably fall (Armstrong's lab work), and rapid losses beyond 5% with heat exposure are emergencies. Rehydrate with sodium-containing fluids, ~1.25–1.5 L per kilogram lost, spread over time — plain water alone re-dilutes and triggers urination before restoration.
Formula
For general information only — not medical advice, a diagnosis or a treatment plan. Consult a qualified healthcare professional before making health, diet, medication or exercise decisions.
Body-weight loss as dehydration percent with the performance and medical bands at each level. The Dehydration Percentage Calculator is a free, private dehydration percentage tool — every result computes instantly in your browser with no sign-up and no data upload.
About Dehydration Percentage Calculator
Acute weight drops over hours are essentially all water — the 2% line is where cognition and endurance measurably fall (Armstrong's lab work), and rapid losses beyond 5% with heat exposure are emergencies. It applies % = (normal − current) ÷ normal × 100. Use the Dehydration Percentage Calculator to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Dehydration Percentage Calculator
- 1Enter your details in the Dehydration Percentage Calculator input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Dehydration Percentage Calculator?
- ✓Instant dehydration percentage result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Armstrong LE et al., J Nutr 2012 — mild dehydration and mood/cognition)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Dehydration Percentage Calculator work?+
Acute weight drops over hours are essentially all water — the 2% line is where cognition and endurance measurably fall (Armstrong's lab work), and rapid losses beyond 5% with heat exposure are emergencies. The calculation uses the formula: % = (normal − current) ÷ normal × 100. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Dehydration Percentage Calculator accurate, and what is it based on?+
The method is traceable to authoritative sources, including Armstrong LE et al., J Nutr 2012 — mild dehydration and mood/cognition; Shirreffs SM et al., Br J Nutr 1996 — post-exercise rehydration volume. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Dehydration Percentage Calculator free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general information only and is not medical advice. Always consult a qualified healthcare professional before making health decisions.
What can I use the Dehydration Percentage Calculator for?+
It's commonly used for dehydration percentage, 2 percent dehydration, fluid loss body weight. Body-weight loss as dehydration percent with the performance and medical bands at each level.
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