Prescon - Pressure Unit Tool
Prescon converts a pressure value from one unit to another the moment you type. It covers the units you meet in science, engineering, weather and everyday life: pascals from Pa up to GPa, bar and millibar, standard atmospheres, millimetres and inches of mercury, water columns, psi, ksi, pounds per square foot, Torr and micrometres of mercury.
Pressure is one of those quantities where every field has its own favourite unit. Weather maps use hectopascals, tyre gauges use psi or bar, vacuum pumps use Torr or mbar, and blood pressure is in mmHg. Prescon puts them side by side so you don't have to look up conversion factors.
It also includes a few small calculators: air pressure at a given altitude, water pressure at a depth, how strong a vacuum is, a blood pressure category reference and a simple pressure-trend check. Everything runs in your browser with no account.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Prescon
- Enter a value. Type a number into the input field on the main screen.
- Choose the units. Pick the unit you are converting from and the unit you want. The result card updates instantly.
- Copy the result. Tap the copy icon on the result card to copy the converted value.
- Try a pressure tool. Swipe through the Pressure Tools cards at the top and tap Altitude, Water Depth, Blood Pressure, Vacuum or Pressure Trend to open a small calculator.
- Altitude and depth. Enter a height in metres to see standard air pressure there, or a water depth to see the water pressure it adds.
- Vacuum and trend. Enter an absolute pressure to see the vacuum percentage and level. In Pressure Trend, enter barometer readings in hPa one after another; it keeps the last six and says whether pressure is rising, steady or falling.
Features
- 19 pressure units: Pa, hPa, kPa, MPa, GPa, bar, mbar, atm, mmHg, cmHg, inHg, mmH2O, cmH2O, mH2O, psi, ksi, psf, Torr, μmHg
- Real-time conversion as you type
- Copy the result to the clipboard
- Altitude pressure calculator based on the International Standard Atmosphere
- Water depth pressure calculator
- Vacuum percentage calculator
- Blood pressure category reference
- Pressure trend analyser
- Interface in many languages
A short guide to pressure units
What pressure is
Pressure is force spread over an area. The SI unit, the pascal (Pa), is one newton per square metre, which is tiny: a sheet of paper lying on a desk presses down with roughly 1 Pa. That is why everyday values use kilopascals (kPa, thousands of pascals) or hectopascals (hPa, hundreds). Standard sea-level air pressure is 101,325 Pa, which is 1013.25 hPa, 101.325 kPa, 1.01325 bar, 1 atm, 760 mmHg or about 14.7 psi.
Who uses which unit
Meteorologists use hPa, which conveniently equals the older millibar. Tyre pressures are given in psi in the United States and in bar or kPa in much of the world; a typical car tyre at around 32 psi is about 2.2 bar. Medicine still uses millimetres of mercury for blood pressure. Vacuum technology uses Torr (almost exactly 1 mmHg) or mbar, and structural engineers use MPa or ksi for material strength.
Absolute and gauge pressure
A tyre gauge reading of 2.2 bar means 2.2 bar above the surrounding air. That is gauge pressure; the absolute pressure inside the tyre is about 3.2 bar. Vacuum readings are usually absolute. Prescon's unit conversion doesn't change the reference, so convert gauge to gauge and absolute to absolute. Similarly, the water-depth tool shows the pressure added by the water (about 0.98 bar per 10 m of fresh water); add atmospheric pressure for the absolute value.
Pressure and altitude
Air pressure falls as you climb because there is less air above you. In the International Standard Atmosphere it drops to about 900 hPa at 1,000 m and roughly half of sea-level pressure near 5,500 m. Real weather shifts these values by a few percent, which is why altimeters need regular adjustment.
Barometric trends matter more than single readings for weather: a fall of several hectopascals over three hours often signals an approaching low and unsettled weather, while steadily rising pressure usually means improving conditions.
Frequently asked questions
How accurate are the conversions?
They use standard conversion factors and are accurate for everyday, educational and most engineering work. Always check critical values against your equipment's specifications.
Does the water depth tool include air pressure?
No. It shows the pressure from the water column alone, using fresh water at 1,000 kg/m³. Seawater is a few percent denser.
Can I use the blood pressure tool for health decisions?
No. It shows a rough category for the numbers you enter, for reference. Blood pressure should be measured properly and interpreted by a doctor.
Is anything saved?
No account is needed and conversions aren't stored. Close the page and nothing remains except your basic app preferences in this browser.
What is different from the phone app?
The tools are the same. The iPhone and Android apps show ads that a subscription removes; the web version has no ads or purchases.
Limitations of the web version
- No conversion history
- Water depth uses fresh water and shows the added pressure only
- Altitude results follow the standard atmosphere, not current weather
- Calculator screens are in English
Disclaimer
Prescon is a unit conversion and reference tool. The blood pressure category is for general reference only and is not medical advice; consult a doctor about your blood pressure. Verify critical engineering values against official specifications.
Phone app
Prescon is also available as an app for phones and tablets: