How to Calculate Your Sweat Rate at Home (Scale and Bottle)
A scale, a bottle and a timer are enough to measure how much fluid you lose in a session. Here's the check, a worked example, and how to turn the number into a drinking plan.
You can calculate your sweat rate at home with a scale, a bottle and a timer. Weigh yourself before and after a session, add what you drank, then divide by the hours you trained. The answer is litres per hour, and it's the number a personal drinking plan starts from. Below: the check, a worked example, and how to use the result at your next practice or game.
Your sweat rate is a number you can measure.
Sweat helps your body manage heat. It also means you lose fluid, and how much you lose depends on you, the session and the conditions.
The National Athletic Trainers' Association (NATA) puts the spread in its position statement on fluid replacement. Adult sweat rates during exercise range from 0.5 to 4.0 litres an hour. That's an eightfold gap. A rule like "drink a bottle an hour" can be too much for one athlete and too little for another.
Read those as ranges across many people, not as a prediction for you. They're the reason NATA recommends measuring each athlete's own sweat rate instead of leaning on averages.
What you need before you start.
- A bathroom scale that reads to 0.1 kg (or 0.2 lb).
- A bottle you can measure. Note its size in mL (a 600 mL bottle is about 20 oz).
- A towel, and the same light clothing for both weigh-ins.
- A timer or clock to record the session length.
Pick a normal session, not a recovery skate. Write down the conditions: indoors or out, cold rink or hot gym, how hard you worked.
If you use the bathroom mid-session, measure the urine volume and subtract it in your calculation. The other option is to weigh yourself right before and right after that stop. If you can't do either, run the check on another day.
How to calculate your sweat rate at home.
Use the toilet if you need to, strip to minimal clothing, towel off any sweat and step on the scale. Write down your weight in kilograms. Fill your bottle and note the volume.
Drink as you usually would. Don't wipe your bottle clean and top it up mid-session without noting it. Track exactly how much you drank, and how long you trained in hours.
Towel off, wear the same clothing and step on the same scale. Then run the numbers below.
NATA's sweat-rate equation, written out:
Body mass before (kg), minus body mass after (kg), plus fluid you drank (L), minus urine (L), if any.
Sweat loss (L) divided by session length (hours).
Weights are in kilograms and fluid in litres, so the answer lands in litres per hour. To convert pounds, divide by 2.2.
A worked example.
A skater weighs 72.4 kg (159.6 lb) before a 90-minute practice. She drinks one 600 mL bottle (about 20 oz) and doesn't use the bathroom. After, she weighs 71.3 kg (157.2 lb).
- Weight lost: 72.4 minus 71.3 = 1.1 kg.
- Add fluid drunk: 1.1 + 0.6 = 1.7 L of sweat loss.
- Session length: 90 minutes = 1.5 hours.
- Sweat rate: 1.7 divided by 1.5 = about 1.1 L/h (roughly 38 oz an hour).
She drank 0.6 L but lost 1.7 L. The gap is why the scale reads lighter at the end. This is one number from one session, so repeat it in different conditions before you trust it.
Turn the number into a drinking plan.
NATA's guidance is to drink enough to approximate your own sweat losses while avoiding both big fluid deficits and drinking more than you need. The goal isn't a perfect match. It's to limit how far behind you fall.
Take your sweat rate in mL per hour. Our skater's 1.1 L/h is about 1,100 mL an hour.
Spread over four 15-minute blocks, 1,100 mL is about 280 mL (9.5 oz) per block. Hockey stoppages rarely fall every 15 minutes, so treat this as arithmetic, not a schedule. Drink at the breaks you actually get, and don't force fluid you can't comfortably take on.
If you get three real breaks in a 90-minute session, sip from a bottle at each one. Check how much is left afterward and adjust next time.
Weigh in after your next session using the plan. If you finished lighter by a lot, you fell behind. If your weight went up, you drank more than you sweated. Adjust by small steps.
Why your teammate's number won't match yours.
Body size, fitness, heat, humidity, intensity and gear all change how much you sweat. So does the position you play and how many minutes you skate. Your numbers from a cold rink in January won't match an August tournament in a hot arena.
Sodium varies too. NATA reports that sweat sodium concentrations range from 10 to 100 mEq/L in exercise. The scale check doesn't measure sodium, only fluid. NATA's position is that individual advice should rest on individual data, so a sports dietitian can help you interpret your numbers for your sport and season.
Sweat rate FAQ.
How long should the test session be?
Anywhere from 60 to 90 minutes of normal training works well, and longer is fine. Very short sessions give small weight changes that are hard to read on a home scale.
Do I count a bathroom break?
Yes. Urine you pass during the session lowers your after-weight, so if you skip the adjustment, your sweat loss will be overestimated. Measure the urine and subtract that volume, or weigh before and after the stop. Otherwise, repeat the check on another day.
Can I do this in a hockey game?
Yes, though games are harder to measure. Track bottle volume, ice time and bench time as best you can. Practices give cleaner numbers, so start there.
How often should I repeat the check?
Repeat it when conditions change: a new season, a hot arena, a tougher training block. One session gives you a starting point. A few sessions give you a range.
Measure it, then plan around it.
A scale, a bottle and a notebook give you your own sweat rate. Use it to plan your bottles for the next practice, then check how the plan worked. When you're ready to build the routine, look at what fits your session.
Explore the hydration collectionReferences & further reading
PubMed record for the NATA position statement on fluid replacement
Disclaimer: This article is for general education and is not medical advice. If you have a health concern, talk to a qualified health professional.
