Convert Inch of water to Pound per square inch
1 inch of water = 0.03612729 pound per square inch (psi). For example, 10 inch of water = 0.3612729 pound per square inch and 100 inch of water = 3.612729 pound per square inch. Type any value below to convert inch of water to pound per square inch both ways — it runs entirely in your browser.
Quick answer: Inch of water to Pound per square inch
1 Inch of water = 0.03612729 Pound per square inch (inH₂O → psi). To convert inch of water to pound per square inch, multiply by 0.03612729. To convert pound per square inch to inch of water, multiply by 27.6799. The converter at the top does this instantly and both ways; the sections below give the formula, worked examples, a full conversion chart and answers to the most common inch of water-to-pound per square inch questions.
How to convert Inch of water to Pound per square inch
To convert inch of water to pound per square inch, multiply the number of inch of water by the conversion factor 0.03612729, because 1 inH₂O = 0.03612729 psi. The conversion is linear, so the same factor works for any value — whole numbers, decimals or fractions. For the reverse direction, 1 psi = 27.6799 inH₂O, so you divide by 0.03612729 (or multiply by 27.6799) to turn pound per square inch back into inch of water.
psi = inH₂O × 0.03612729 ·
inH₂O = psi × 27.6799
- Write down the value you want to convert, in inch of water.
- Multiply it by 0.03612729.
- The result is the same area/length/quantity expressed in pound per square inch.
Inch of water to Pound per square inch — worked examples
Each row shows the exact arithmetic so you can follow the conversion step by step. For example, 5 inch of water is 0.1806365 pound per square inch because 5 inH₂O × 0.03612729 = 0.1806365 psi.
| Inch of water | Calculation | Pound per square inch |
|---|---|---|
| 1 inH₂O | 1 inH₂O × 0.03612729 = 0.03612729 psi | 0.03612729 psi |
| 2 inH₂O | 2 inH₂O × 0.03612729 = 0.07225458 psi | 0.07225458 psi |
| 3 inH₂O | 3 inH₂O × 0.03612729 = 0.1083819 psi | 0.1083819 psi |
| 5 inH₂O | 5 inH₂O × 0.03612729 = 0.1806365 psi | 0.1806365 psi |
| 7 inH₂O | 7 inH₂O × 0.03612729 = 0.252891 psi | 0.252891 psi |
| 10 inH₂O | 10 inH₂O × 0.03612729 = 0.3612729 psi | 0.3612729 psi |
| 12 inH₂O | 12 inH₂O × 0.03612729 = 0.4335275 psi | 0.4335275 psi |
| 15 inH₂O | 15 inH₂O × 0.03612729 = 0.5419094 psi | 0.5419094 psi |
| 20 inH₂O | 20 inH₂O × 0.03612729 = 0.7225458 psi | 0.7225458 psi |
| 25 inH₂O | 25 inH₂O × 0.03612729 = 0.9031823 psi | 0.9031823 psi |
| 50 inH₂O | 50 inH₂O × 0.03612729 = 1.806365 psi | 1.806365 psi |
| 100 inH₂O | 100 inH₂O × 0.03612729 = 3.612729 psi | 3.612729 psi |
Common Inch of water to Pound per square inch conversions
These are the inch of water-to-pound per square inch values people look up most often. Every figure is computed from the exact factor, so you can rely on them for quick reference:
- 1 inch of water = 0.03612729 pound per square inch
- 2 inch of water = 0.07225458 pound per square inch
- 2.5 inch of water = 0.09031823 pound per square inch
- 3 inch of water = 0.1083819 pound per square inch
- 4 inch of water = 0.1445092 pound per square inch
- 5 inch of water = 0.1806365 pound per square inch
- 6 inch of water = 0.2167638 pound per square inch
- 7 inch of water = 0.252891 pound per square inch
- 8 inch of water = 0.2890183 pound per square inch
- 9 inch of water = 0.3251456 pound per square inch
- 10 inch of water = 0.3612729 pound per square inch
- 12 inch of water = 0.4335275 pound per square inch
- 15 inch of water = 0.5419094 pound per square inch
- 20 inch of water = 0.7225458 pound per square inch
- 25 inch of water = 0.9031823 pound per square inch
- 30 inch of water = 1.083819 pound per square inch
- 50 inch of water = 1.806365 pound per square inch
- 75 inch of water = 2.709547 pound per square inch
- 100 inch of water = 3.612729 pound per square inch
- 200 inch of water = 7.225458 pound per square inch
- 500 inch of water = 18.06365 pound per square inch
- 1000 inch of water = 36.12729 pound per square inch
Inch of water to Pound per square inch conversion chart (both directions)
The chart below converts inch of water to pound per square inch and pound per square inch to inch of water side by side, so it works whichever way you need. 1 inch of water = 0.03612729 pound per square inch, and 1 pound per square inch = 27.6799 inch of water.
| Inch of water → Pound per square inch | Pound per square inch → Inch of water |
|---|---|
| 0.25 inH₂O = 0.009031823 psi | 0.25 psi = 6.919976 inH₂O |
| 0.5 inH₂O = 0.01806365 psi | 0.5 psi = 13.83995 inH₂O |
| 1 inH₂O = 0.03612729 psi | 1 psi = 27.6799 inH₂O |
| 2 inH₂O = 0.07225458 psi | 2 psi = 55.35981 inH₂O |
| 3 inH₂O = 0.1083819 psi | 3 psi = 83.03971 inH₂O |
| 4 inH₂O = 0.1445092 psi | 4 psi = 110.7196 inH₂O |
| 5 inH₂O = 0.1806365 psi | 5 psi = 138.3995 inH₂O |
| 6 inH₂O = 0.2167638 psi | 6 psi = 166.0794 inH₂O |
| 7 inH₂O = 0.252891 psi | 7 psi = 193.7593 inH₂O |
| 8 inH₂O = 0.2890183 psi | 8 psi = 221.4392 inH₂O |
| 9 inH₂O = 0.3251456 psi | 9 psi = 249.1191 inH₂O |
| 10 inH₂O = 0.3612729 psi | 10 psi = 276.799 inH₂O |
| 12 inH₂O = 0.4335275 psi | 12 psi = 332.1589 inH₂O |
| 15 inH₂O = 0.5419094 psi | 15 psi = 415.1986 inH₂O |
| 20 inH₂O = 0.7225458 psi | 20 psi = 553.5981 inH₂O |
| 25 inH₂O = 0.9031823 psi | 25 psi = 691.9976 inH₂O |
| 30 inH₂O = 1.083819 psi | 30 psi = 830.3971 inH₂O |
| 40 inH₂O = 1.445092 psi | 40 psi = 1,107.196 inH₂O |
| 50 inH₂O = 1.806365 psi | 50 psi = 1,383.995 inH₂O |
| 75 inH₂O = 2.709547 psi | 75 psi = 2,075.993 inH₂O |
| 100 inH₂O = 3.612729 psi | 100 psi = 2,767.99 inH₂O |
| 150 inH₂O = 5.419094 psi | 150 psi = 4,151.986 inH₂O |
| 200 inH₂O = 7.225458 psi | 200 psi = 5,535.981 inH₂O |
| 250 inH₂O = 9.031823 psi | 250 psi = 6,919.976 inH₂O |
| 500 inH₂O = 18.06365 psi | 500 psi = 13,839.95 inH₂O |
| 1000 inH₂O = 36.12729 psi | 1000 psi = 27,679.9 inH₂O |
Inch of water vs Pound per square inch: which is bigger?
A pound per square inch is the larger unit: one pound per square inch equals 27.6799 inch of waters. Put another way, you need 27.6799 inch of waters to make a single pound per square inch.
What is a Inch of water? History, origin and usage
The inch of water is the imperial counterpart of the millimetre of water, and it became entrenched in North American heating and ventilation practice, where it is usually written "inches WC" for water column. Gas utilities adopted it because household gas supply pressures are small enough that a water manometer reads them comfortably.
Inches of water are used for duct pressure and fan static pressure in heating and air-conditioning, for natural-gas appliance supply pressure, and for cleanroom and filter differential pressures.
Residential natural gas is typically delivered at around 7 inches of water column — a pressure so low that it would barely register on a tyre gauge. An inch of water is exactly 25.4 millimetres of water.
What is a Pound per square inch? History, origin and usage
Pounds per square inch grew directly out of the steam age: boiler safety valves were rated by how many pounds of weight it took to hold them shut over a known area, and the unit survived into every later technology that Britain and the United States industrialised. It never went through a formal international definition of its own — instead it became exact in 1959, when the yard-and-pound agreement fixed the pound and the inch exactly, and again through the fixing of standard gravity, which pins down what a "pound of force" means.
Psi is the standard pressure unit in the United States and remains widely understood in Britain, India and elsewhere: tyre pressures, air compressors, pressure washers, water mains, hydraulic lines and scuba tanks. Car tyres are commonly inflated to around 30 to 35 psi.
Psi is exactly defined but its value in pascals is a decimal that repeats forever, so any written figure is necessarily rounded somewhere. Gauges usually read gauge pressure — the amount above surrounding air — which is why a flat tyre reads zero rather than about 14.7.
Convert 1 Inch of water to other units
It can help to see a inch of water next to the other units it is commonly compared with. One inch of water (inH₂O) is equal to:
| 1 Inch of water equals | Unit |
|---|---|
| 249.0889 Pa | Pascal |
| 2.490889 hPa | Hectopascal |
| 0.2490889 kPa | Kilopascal |
| 0.0002490889 MPa | Megapascal |
| 2.490889 mbar | Millibar |
| 0.002490889 bar | Bar |
| 0.002458316 atm | Standard atmosphere |
| 1.86832 Torr | Torr |
| 1.86832 mmHg | Millimetre of mercury |
| 0.07355591 inHg | Inch of mercury |
| 25.4 mmH₂O | Millimetre of water |
| 0.03612729 psi | Pound per square inch |
| 0.00254 kgf/cm² | Kilogram-force per square centimetre |
Convert 1 Pound per square inch to other units
One pound per square inch (psi) is equal to:
| 1 Pound per square inch equals | Unit |
|---|---|
| 6,894.757 Pa | Pascal |
| 68.94757 hPa | Hectopascal |
| 6.894757 kPa | Kilopascal |
| 0.006894757 MPa | Megapascal |
| 68.94757 mbar | Millibar |
| 0.06894757 bar | Bar |
| 0.06804596 atm | Standard atmosphere |
| 51.71493 Torr | Torr |
| 51.71493 mmHg | Millimetre of mercury |
| 2.036021 inHg | Inch of mercury |
| 703.0696 mmH₂O | Millimetre of water |
| 27.6799 inH₂O | Inch of water |
| 0.07030696 kgf/cm² | Kilogram-force per square centimetre |
Tips for converting Inch of water to Pound per square inch
- To go from inch of water to pound per square inch, multiply by 0.03612729; to go back, divide by 0.03612729 (or multiply by 27.6799).
- For a quick mental estimate, remember that 1 inch of water ≈ 0.03612729 pound per square inch, so 10 inch of water ≈ 0.3612729 pound per square inch.
- The converter above keeps full precision; the tables round for readability, so use the tool for exact figures.
- Both fields update live as you type — change either side to convert in that direction.
How to use this Inch of water to Pound per square inch converter
Type a number into the Inch of water field and the equivalent in Pound per square inch appears instantly — there is no “convert” button to press and nothing is sent to a server, so it works offline once the page has loaded and is safe for any data. You can also type into the Pound per square inch field to convert the other way (pound per square inch to inch of water). Use the swap control to flip the two units, and copy the result with a single click. Because the calculation runs in your browser with full floating-point precision, the converter is more exact than the rounded figures shown in the reference chart above — use the chart for quick look-ups and the tool for precise work.
Accuracy and method
Every figure on this page — the formula, the worked examples, the conversion chart and the “convert to other units” tables — is computed from a single verified conversion factor (1 inH₂O = 0.03612729 psi), never copied from a hand-typed lookup table that could drift. That factor is derived from each unit’s definition in terms of a common base unit, and an automated check re-verifies all of the site’s factors on every update, so the numbers here stay correct over time. This matters for inch of water-to-pound per square inch conversions because a small rounding error in a published table compounds quickly at larger quantities; computing from the exact factor avoids that.
Sources
- NIST Special Publication 811 — Guide for the Use of the SI — publishes the exact metric equivalents of the customary pressure units. A psi is one pound of force over one square inch, and the 1959 international yard-and-pound agreement fixes the pound at exactly 0.453 592 37 kilogram and the inch at exactly 0.0254 metre, while standard gravity is fixed at exactly 9.806 65 m/s² — so psi, inches of mercury and inches of water are defined exactly rather than measured.
- BIPM — The International System of Units (SI Brochure) — the defining document for the SI, published by the International Bureau of Weights and Measures. It fixes the base unit that this conversion resolves to, which is why the factor here can be exact rather than approximate.
Pressure factors here come from fixed definitions, anchored to the pascal: a bar is exactly 100,000 Pa, one atmosphere is exactly 101,325 Pa, a torr is exactly a 760th of an atmosphere, and psi is built from the exact pound and the exact inch. Two of them — psi and the torr — work out to decimals that repeat forever, so where a number is shown rounded it is marked, not quietly trimmed.
Frequently asked questions
- How many pound per square inch are in 1 inch of water?
- 1 inch of water = 0.03612729 pound per square inch (psi). To convert any number of inch of water to pound per square inch, multiply by 0.03612729.
- How do I convert inch of water to pound per square inch?
- Multiply the number of inch of water by 0.03612729. For example, 10 inch of water = 10 × 0.03612729 = 0.3612729 pound per square inch, and 25 inch of water = 0.9031823 pound per square inch.
- How many inch of water are in 1 pound per square inch?
- 1 pound per square inch = 27.6799 inch of water. So to convert pound per square inch back to inch of water, multiply by 27.6799.
- What is the formula to convert inch of water to pound per square inch?
- pound per square inch = inch of water × 0.03612729. The reverse formula is inch of water = pound per square inch × 27.6799.
- How much is 100 inch of water in pound per square inch?
- 100 inch of water = 3.612729 pound per square inch. (And 1000 inch of water = 36.12729 pound per square inch.)
- Which is bigger, a inch of water or a pound per square inch?
- A pound per square inch is larger: 1 pound per square inch = 27.6799 inch of water.
- Is this inch of water to pound per square inch converter accurate?
- Yes — every value is computed from the exact 0.03612729 psi per inH₂O factor (not rounded look-up tables), and the factors are re-verified automatically on every update.
- Can I convert pound per square inch to inch of water too?
- Yes. The converter works both ways — enter a value in either field. 1 pound per square inch = 27.6799 inch of water.