Torr to Millibar Converter

How it is calculated

The conversion uses the exact definition that one standard atmosphere is 760 torr and 1,013.25 mbar, so 1 torr = 101325 ÷ 76000 mbar, which is 1.33322 mbar when written to six significant figures. Torr to millibar: mbar = torr × 1.33322…. Millibar to torr: torr = mbar ÷ 1.33322…, about 0.750062 torr per millibar. The direction selector (torr2mbar or mbar2torr) picks the formula; the default is torr to mbar. The value must be zero or more, and negative values give no result. Results are rounded to three decimals, so very small pressures lose precision, and a second line converts the answer back as a check. The factor shown in the rate line is a rounded display of the exact one used in the calculation.

Common mistakes

• Choosing the wrong direction. A weather reading of 1,013 mbar entered with torr to mbar selected gives 1,350.556, which is not a plausible surface pressure; switch the direction to mbar to torr to get 759.8 torr.
• Treating torr as identical to mmHg in precise work. They are very close, but not exactly equal, which can matter in metrology but not on a normal gauge.
• Entering a vacuum pressure in millitorr as if it were torr. A millitorr is a thousandth of a torr, so 5 mTorr must be entered as 0.005 torr; and since the result is shown to three decimals, 0.005 torr appears as only 0.007 mbar, so very low pressures are too coarse here.
• Entering a negative gauge reading. Pressure values here must be absolute and non-negative; a vacuum gauge reading below atmosphere has to be converted to an absolute value first.
• Confusing millibar with hectopascal conversions. They are the same size (1 mbar = 1 hPa), so no factor is needed between them; the factor belongs only to the torr step.