Gauges, transmitters and pump curves use different pressure units. Enter a value once and see it in every common unit, including inches of water at both 39.2 °F and 68 °F, since transmitters differ.
Pressure Unit Converter
Formula
Value in new unit = Value x (Pa per old unit) / (Pa per new unit) 1 psi = 6,894.757 Pa 1 kPa = 1,000 Pa 1 bar = 100,000 Pa 1 ft of water (39.2 °F) = 2,988.98 Pa 1 in of water (39.2 °F) = 249.082 Pa 1 in of water (68 °F) = 248.64 Pa 1 in of mercury (32 °F) = 3,386.38 Pa 1 m of water = 9,806.65 Pa So 1 psi = 2.307 ft = 27.68 in of water = 2.036 in Hg
Inputs used
- Pressure
- From unit
Worked example (fictional plant data)
- Convert 10 psi
- kPa = 10 x 6,894.757 / 1,000 = 68.9476
- ft of water = 10 x 6,894.757 / 2,988.98 = 23.067
- in of water = 10 x 6,894.757 / 249.082 = 276.807
- in of mercury = 10 x 6,894.757 / 3,386.38 = 20.360
Cautions
- Keep gauge and absolute pressure separate. psia = psig + barometric pressure.
- Water column units depend on the reference temperature. The difference is small (about 0.2%) but shows up in a tight calibration.
- For a liquid other than water, divide feet of water by the specific gravity to get feet of that liquid.
References
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.8 (factors for pressure units).
Results are estimates for operator and technician use. Equations follow the references above; always check against the instrument manual, your calibration procedure and plant data.