Convert between inHg, hPa, mbar, mmHg, and atm with weather condition indicators.
This tool converts a barometric pressure reading into inches of mercury (inHg), hectopascals (hPa), millibars (mbar), millimeters of mercury (mmHg), and standard atmospheres (atm) at once, using fixed physical conversion constants rather than a live weather feed. It also attaches a qualitative label, such as low or high pressure, based on where the value falls relative to standard sea-level pressure. The detail people miss most: hPa and mbar are the same unit by definition, so those two fields will always match exactly, and the weather label reflects only the instantaneous value, not whether pressure is rising or falling.
A concrete input and expected output from the current implementation.
Input
29.92 inHg
Expected output
1013.21 hPa, 1013.21 mbar, 759.97 mmHg, 1.00 atm
29.92 inHg is very close to standard sea-level pressure (29.9213 inHg = 1013.25 hPa), so scaling by the fixed inHg-to-hPa and inHg-to-mmHg ratios (33.8639 and 25.4 respectively) lands just under one full atmosphere.
Every value derives from one physical relationship: 1 standard atmosphere equals 1013.25 hPa (also 1013.25 mbar), 29.9213 inHg, and 760 mmHg. Entering a number in any field recalculates the other four using these ratios - for example, inHg to mmHg scales by 25.4, the exact inch-to-millimeter length ratio, since both units measure the height of a mercury column.
Alongside the numeric conversions, the tool assigns a qualitative tag, such as low, normal, or high, by comparing the entered pressure against reference bands centered on standard sea-level pressure of 1013.25 hPa. This label reflects only the single value entered - it has no access to trend data, so it cannot indicate whether pressure is rising, falling, or holding steady.
Because they are the same unit under two names - one millibar has always equaled exactly one hectopascal since the meteorological community adopted SI units. The tool is not making an independent second calculation; it is displaying one value twice under both labels.
No. It only classifies the pressure value you entered against general reference bands, such as low, normal, or high. Actual forecasting depends on how pressure is changing over time, and this tool has no memory of previous readings, so it cannot detect or show a trend.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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