Atmospheres to Inches of Water
Convert atmospheres to inches of water instantly. 1 atm = 406.7824780631 inH2O. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert atmospheres to inches of water
To convert atmospheres to inches of water, multiply by 406.7824780631. The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
inH2O = atm × 406.7824780631
Atmospheres to Inches of Water conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Atmospheres | Inches of Water |
|---|---|
| 1 atm | 406.782478 inH2O |
| 2 atm | 813.564956 inH2O |
| 3 atm | 1,220.35 inH2O |
| 5 atm | 2,033.91 inH2O |
| 10 atm | 4,067.82 inH2O |
| 20 atm | 8,135.65 inH2O |
| 25 atm | 10,169.56 inH2O |
| 50 atm | 20,339.12 inH2O |
| 100 atm | 40,678.25 inH2O |
| 500 atm | 203,391.24 inH2O |
| 1,000 atm | 406,782.48 inH2O |
What is a atmosphere?
The standard atmosphere, defined as exactly 101,325 Pa.
What is a inches of water?
A low-pressure unit used for ventilation and gas appliances.
The formula
inH2O = atm × 406.7824780631
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Atmospheres to Inches of Water
- Type the number of atmospheres you want to convert.
- Read the result in inches of water straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked inches of water to atmospheres page.
Atmospheres to Inches of Water — frequently asked questions
How many inches of water are in a atmosphere?
One atmosphere equals 406.7824780631 inH2O. inH2O = atm × 406.7824780631
What is the formula to convert atmospheres to inches of water?
The formula is inH2O = atm × 406.7824780631. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert inches of water back to atmospheres?
Divide instead of multiplying: one inches of water is 0.0024583163 atm. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this atmospheres to inches of water free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
What people search for
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 19, 2026 · Calculation runs client-side · No data collected · Report an error