Inches of Water to Atmospheres
Convert inches of water to atmospheres instantly. 1 inH2O = 0.0024583163 atm. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert inches of water to atmospheres
To convert inches of water to atmospheres, divide by 406.7824780631 (multiply by 0.0024583163). 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.
atm = inH2O × 0.0024583163
Inches of Water to Atmospheres conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Inches of Water | Atmospheres |
|---|---|
| 1 inH2O | 0.002458 atm |
| 2 inH2O | 0.004917 atm |
| 3 inH2O | 0.007375 atm |
| 5 inH2O | 0.012292 atm |
| 10 inH2O | 0.024583 atm |
| 20 inH2O | 0.049166 atm |
| 25 inH2O | 0.061458 atm |
| 50 inH2O | 0.122916 atm |
| 100 inH2O | 0.245832 atm |
| 500 inH2O | 1.229158 atm |
| 1,000 inH2O | 2.458316 atm |
What is a inches of water?
A low-pressure unit used for ventilation and gas appliances.
What is a atmosphere?
The standard atmosphere, defined as exactly 101,325 Pa.
The formula
atm = inH2O × 0.0024583163
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 Inches of Water to Atmospheres
- Type the number of inches of water you want to convert.
- Read the result in atmospheres 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 atmospheres to inches of water page.
Inches of Water to Atmospheres — frequently asked questions
How many atmospheres are in a inches of water?
One inches of water equals 0.0024583163 atm. atm = inH2O × 0.0024583163
What is the formula to convert inches of water to atmospheres?
The formula is atm = inH2O × 0.0024583163. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert atmospheres back to inches of water?
Divide instead of multiplying: one atmosphere is 406.7824780631 inH2O. 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 inches of water to atmospheres 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