To convert inches of water to torr, multiply by 1.868320395. That factor is the whole relationship: both units measure pressure, so the conversion is a proportion with no offset and no substance-specific constant.
The low-pressure unit for duct static pressure and gas appliances in the US. One millimetre of mercury, used in vacuum work.
Gauge versus absolute. A tyre gauge reading 32 psi means 32 psi above atmospheric, which is about 46.7 psi absolute. Converting the number is straightforward; remembering which zero it was measured from is where the mistakes happen. N/mm² and MPa are the same size, so a drawing quoting either is quoting the same stress. Below the calculator there is a step table for the values people look up most, and a second table putting real pressure figures into torr so the number you get has something to be compared against.
The formula
inches of water- The amount you are converting, in inches of water
1.86832039477- The exact number of torr in one inch of water
torr- The converted result
How it works, step by step
- Enter the value in inches of water.
- It is multiplied by 1.86832039477, the exact factor between the two units.
- The answer is shown in torr, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A domestic water main: 1610 inH₂O in torr
A domestic water main comes to about 1610 inH₂O. Multiplying by the factor: 1610 × 1.86832 = 3008 Torr. Dividing the answer back by 1.86832 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
A steam boiler: 4010 inH₂O in torr
Take a steam boiler, roughly 4010 inH₂O. The conversion is a single multiplication — 4010 × 1.86832 — giving 7491.96 Torr. Because the relationship is proportional, doubling the input doubles the answer to 14,983.9 Torr.
How to read your score
Frequently asked questions
How many torr are in one inch of water?
Exactly 1.86832039477. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert inches of water to torr?
torr = inches of water × 1.86832039477. Reversed, inches of water = torr ÷ 1.86832039477, which is the same as multiplying by 0.535240102715.
Which is the bigger unit, the inch of water or the torr?
The inch of water. One inch of water equals 1.86832 torr.
What does this quantity actually measure?
Both units measure pressure. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a inch of water?
The low-pressure unit for duct static pressure and gas appliances in the US.
What is a torr?
One millimetre of mercury, used in vacuum work.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do inH₂O to Torr in my head?
Plenty of people do this in their head: multiply by 1.9 instead of using the exact factor 1.868320395. At 100 that shortcut gives 190 torr, off by 3.168 torr or about 1.70%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Inches Of Water to torr reference tables
| Inches Of Water | Torr |
|---|---|
| 0.5 inH₂O | 0.93416 Torr |
| 1 inH₂O | 1.86832 Torr |
| 2 inH₂O | 3.73664 Torr |
| 3 inH₂O | 5.60496 Torr |
| 5 inH₂O | 9.3416 Torr |
| 10 inH₂O | 18.6832 Torr |
| 20 inH₂O | 37.3664 Torr |
| 25 inH₂O | 46.708 Torr |
| 50 inH₂O | 93.416 Torr |
| 75 inH₂O | 140.124 Torr |
| 100 inH₂O | 186.832 Torr |
| 250 inH₂O | 467.08 Torr |
| 500 inH₂O | 934.16 Torr |
| 1000 inH₂O | 1868.32 Torr |
| 5000 inH₂O | 9341.6 Torr |
Exact factor: 1 inch of water = 1.86832039477 torr.
| Quantity | inH₂O | Torr |
|---|---|---|
| Sea-level air | 406.8 inH₂O | 760 Torr |
| A car tyre | 885.8 inH₂O | 1655 Torr |
| Blood pressure, systolic | 64.23 inH₂O | 120 Torr |
| A bicycle tyre | 2491 inH₂O | 4654 Torr |
| A domestic water main | 1606 inH₂O | 3000 Torr |
| A steam boiler | 4015 inH₂O | 7501 Torr |
Published reference values, converted with the same factor this page uses.