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Multiple conversions
To convert a pressure from millibar (mbar) to pascals (Pa), multiply by 100.
The factor is exact and definitional: one bar is 100,000 Pa, so a thousandth of it is 100 Pa. This also makes the millibar identical to the hectopascal — 1 mbar = 1 hPa, no rounding involved — which is why weather charts switched labels from mbar to hPa decades ago without a single number changing.
A weather station reports sea-level pressure of 1,013.25 mbar and a lab calculation needs SI units:
That is the standard atmosphere, exactly.
| mbar | Pa |
|---|---|
| 1 | 100 |
| 10 | 1,000 |
| 50 | 5,000 |
| 100 | 10,000 |
| 250 | 25,000 |
| 500 | 50,000 |
| 1,000 | 100,000 |
| 1,013.25 | 101,325 |
The millibar owes its career to two communities at opposite ends of the pressure scale. Meteorology adopted it because atmospheric pressure lands in a tidy range around 1,000 mbar — lows in the 950s, highs in the 1,040s — and although official charts now say hPa, aviation weather (QNH altimeter settings), marine forecasts and hurricane reporting still speak millibars; a storm's central pressure of "915 mb" is 91,500 Pa. Vacuum technology adopted it from the other side: pump specifications and process recipes across European industry quote chamber pressures in mbar, running from atmospheric down to 10⁻⁹ mbar and below, where the pascal equivalents (10⁻⁷ Pa) are just as convenient but historically less used in datasheets.
The conversion itself is exact, so the only real pitfall is neighborly confusion between the units this page does not convert: a millibar is not a mmHg (1 mbar = 0.750 mmHg) and not a psi. Weather reports in North America compound the risk by quoting inches of mercury to the public and millibars to aviation — 29.92 inHg and 1,013 mbar are the same standard atmosphere wearing two costumes.
To convert a pressure from millibars (mbar) to kilopascals (kPa), divide by 10.
The relationship is exact: one bar is 100,000 Pa, so a millibar is 100 Pa, and ten of those make one kilopascal. The most useful anchor is standard atmospheric pressure — 1,013.25 mbar = 101.325 kPa — which also shows why weather charts and engineering documents differ only by a decimal point.
A weather station reports a barometric pressure of 1,018 mbar, and a building-ventilation calculation needs it in kilopascals:
Reverse direction: a process specification of 95 kPa absolute is 950 mbar.
| mbar | kPa |
|---|---|
| 1 | 0.1 |
| 100 | 10 |
| 500 | 50 |
| 950 | 95 |
| 1,013.25 | 101.325 |
| 1,050 | 105 |
The millibar is the meteorologist's unit — synoptic charts, storm reports and older aviation weather all speak mbar (and its exact SI twin, the hectopascal: 1 mbar = 1 hPa). The kilopascal is the engineer's unit — HVAC design, process instrumentation, building codes and thermodynamic property tables. The two communities describe the same atmosphere, so the conversion appears whenever weather data feeds an engineering calculation: correcting a fan curve or gas flow measurement to site barometric pressure, converting a hurricane's 920 mbar central pressure for a structural load model, or setting the ambient reference of an absolute-pressure transmitter from the local forecast. Since the shift is a single decimal place, the real risk is not arithmetic but unit confusion with the bar itself: 950 mbar is 0.95 bar and 95 kPa, and all three describe the same slightly-below-standard day. A converted value that lands near 100 when the input was near 1,000 is almost certainly right; anything else deserves a second look.
To convert from millibar (mbar) to megapascal (MPa), use the following formula:
megapascal (MPa)
= 110 × 11000× millibar (mbar)
= 1104× millibar (mbar)
= 10-4× millibar (mbar)
To convert from millibar (mbar) to hectopascal (hPa), use the following formula:
hectopascal (hPa)
= 110 × 10× millibar (mbar)
= 1× millibar (mbar)
To convert a pressure from millibar (mbar) to bar, divide by 1,000 — that is, multiply by 0.001.
Exact by the meaning of the prefix: a millibar is one thousandth of a bar. Equivalently, since 1 mbar = 1 hPa, this is also the hPa-to-bar conversion.
A weather chart shows a deep low of 960 mbar and a calculation set up in bar needs the value:
| mbar | bar |
|---|---|
| 1 | 0.001 |
| 10 | 0.01 |
| 100 | 0.1 |
| 500 | 0.5 |
| 1,000 | 1 |
| 1,013.25 | 1.01325 |
| 1,050 | 1.05 |
The arithmetic here cannot fail except by decimal slip, so the useful content is the anchor: 1,013.25 mbar = 1.01325 bar = one standard atmosphere, the reference that ties weather-report numbers to engineering ones. Everyday sea-level pressure wobbles a few percent around it, which is why atmospheric values in bar are always 0.9-something or 1.0-something — a weather number converted to bar that comes out as 9.6 or 0.096 has had its decimal point mislaid, and the sanity check takes one second. The same anchor guards vacuum work from the opposite direction: a "millibar-range" process at 5 mbar is 0.005 bar, three decades below atmosphere, and writing it in bar mostly serves to feed formulas that want a consistent unit before conversion to pascals. As with every pressure conversion, gauge, absolute and differential character ride along unchanged — barometric pressures are absolute by nature, and stay absolute in bar.
To convert from millibar (mbar) to torr (torr), use the following formula:
torr (torr)
= 110 × 760000101325× millibar (mbar)
= 0.7500616827041697508× millibar (mbar)
To convert from millibar (mbar) to meter of water @ 4°C (mH2O), use the following formula:
meter of water @ 4°C (mH2O)
= 110 × 19.80665× millibar (mbar)
= 0.010197162129779282426× millibar (mbar)
To convert pressure from millibars (mbar) to millimeters of mercury (mmHg), multiply by 0.750062.
The factor comes from the definitions of the two units: 1 mbar is exactly 100 Pa, while 1 mmHg is 133.322 Pa (the pressure of a 1 mm column of mercury at 0 °C under standard gravity). Dividing 100 by 133.322 gives 0.750062 — conveniently close to ¾, which makes rough mental conversion easy: take three quarters of the millibar value.
The classic anchor point ties the two scales together:
A weather station reports a deep low-pressure system at 968 mbar. In mmHg:
Reverse direction: divide by 0.750062 (or multiply by 1.33322). A vacuum gauge showing 15 mmHg equals 20 mbar.
| mbar | mmHg |
|---|---|
| 1 | 0.75 |
| 100 | 75.01 |
| 500 | 375.03 |
| 750 | 562.55 |
| 1,000 | 750.06 |
| 1013.25 | 760.00 |
| 1,050 | 787.57 |
Meteorology settled on the millibar (identical to the hectopascal, hPa, that modern forecasts use), while mmHg survives in medicine and vacuum technique — blood pressure, respiratory therapy, freeze-drying and rotary-evaporator recipes are all written in mmHg or its synonym Torr. The conversion appears whenever these worlds touch: calibrating a medical vacuum regulator against a barometric reference, translating an old lab protocol to a modern digital gauge, or comparing aviation weather (hPa/mbar) with cabin-altitude physiology tables (mmHg). Since 1 mbar = 1 hPa exactly, this same page converts hPa to mmHg with no change to the factor.
To convert from millibar (mbar) to pound per square inch (psi), use the following formula:
pound per square inch (psi)
= 110 × 0.00014503768078 × 1000× millibar (mbar)
= 100 × 0.00014503768078× millibar (mbar)
= 0.014503768078× millibar (mbar)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert from millibar (mbar) to kilopound per square inch (ksi), use the following formula:
kilopound per square inch (ksi)
= 110 × 0.00014503768078× millibar (mbar)
= 0.000014503768078× millibar (mbar)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert from millibar (mbar) to Inch of mercury (inHg), use the following formula:
Inch of mercury (inHg)
= 110 × 0.00014503768078 × 10.000491154× millibar (mbar)
= 0.029529980572284863811× millibar (mbar)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
A millibar (mbar) is a metric unit used to measure atmospheric pressure.
It's most commonly used in weather forecasting and reporting.
(Technically, one millibar is equal to 0.1 kilopascal, or kPa).
Meteorologists use millibars as the primary unit to measure and report atmospheric pressure.
On weather maps, you'll see lines called isobars, which connect areas of equal pressure, drawn in millibar intervals.
Standard atmospheric pressure at sea level is about 1013 mbar.
This number is a key benchmark for weather conditions:
Yes, for all practical purposes, a millibar (mbar) and a hectopascal (hPa) are the same.
The two units are used interchangeably.
The conversion is simple: 1 mbar = 1 hPa.
While you'll still see millibars in public weather reports (especially in the U.S.), the hectopascal is the preferred SI (International System of Units) unit for global scientific consistency.
A barometer measures barometric pressure—the weight of the air above you—using millibars.
Watching the change in this reading is key to predicting the weather: