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Loan Calculator
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Sweat Rate Calculator
Calculates your hourly sweat rate from weight lost during a session and shows how much to drink during and afterwards.
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Enter your figures and press Calculate.
In short
Sweat Rate Calculator is a free online tool on inputtesthub.com that calculates your hourly sweat rate from weight lost during a session and shows how much to drink during and afterwards. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.
How to use the Sweat Rate Calculator
- Enter your figures in the input fields.
- The result updates as you type, together with the full working.
- Check the breakdown table to see exactly how the number was reached.
About the Sweat Rate Calculator
The Sweat Rate Calculator calculates your hourly sweat rate from weight lost during a session and shows how much to drink during and afterwards. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- Working out how much to drink on a long ride or run.
- Checking whether you are losing too much in the heat.
- Planning fluid for a race.
Details
| 1 kg lost | ≈ 1 litre of sweat |
|---|---|
| Over 2% loss | Performance falls |
| Rehydration | 1.5 L per kg lost |
| Drink during | ≈ 80% of sweat rate |
The maths behind it
This tool uses Sweat loss = weight lost in kg × 1,000 ml + fluid drunk. Rate = that ÷ hours. Rehydrate with about 1.5 litres per kilogram lost. Every intermediate value is shown on screen, so the result can be checked by hand.
Losing more than about 2% of body weight measurably reduces performance and in heat raises real risk. Drinking far beyond your sweat rate is not safer either — hyponatraemia from over-drinking during long endurance events is dangerous, which is why "drink to thirst" replaced "drink as much as possible".
Frequently asked questions
Are there any usage caps on the Sweat Rate Calculator?
No charge and no sign-up. There is no free tier to run out of because there is no paid tier — inputtesthub.com is funded by advertising rather than by metering the tool.
Can you see what I put into this tool?
No. The Sweat Rate Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
Can I check the maths myself?
It uses Sweat loss = weight lost in kg × 1,000 ml + fluid drunk. Rate = that ÷ hours. Rehydrate with about 1.5 litres per kilogram lost. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What is the Sweat Rate Calculator used for?
In practice it gets used for three things: working out how much to drink on a long ride or run. Checking whether you are losing too much in the heat. Planning fluid for a race. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there anything to watch out for?
Losing more than about 2% of body weight measurably reduces performance and in heat raises real risk. Drinking far beyond your sweat rate is not safer either — hyponatraemia from over-drinking during long endurance events is dangerous, which is why "drink to thirst" replaced "drink as much as possible".
Which values should I know?
1 kg lost is ≈ 1 litre of sweat. Over 2% loss is Performance falls. Rehydration is 1.5 L per kg lost. These are printed on the page itself, so you do not have to take them on trust.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.
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