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Is 1013 hPa high or low?

Neither. 1013 hPa (1013 mb) is 29.91 inHg, essentially the standard atmosphere of 1013.25 hPa (29.92 inHg), and it sits in the middle of the Normal zone. 1000 hPa (29.53 inHg) is about 13 hPa (0.4 inHg) below that — in the Low zone, but not an extreme reading.

hPa reading chart: 970 to 1050

Find your number, read across for inHg and for the pressure zone it falls in. The inHg column uses 1 hPa = 0.02953 inHg, rounded to two decimals, and the zones are the fixed sea-level bands on /methodology. Where a reading lands exactly on a zone boundary, that page does not say which zone owns it, so the table says “on the line between” the two.

These zones are interpretive conventions, not a standard, and the cut points vary between sources. For the full range discussion see what is normal barometric pressure; for where “low” and “high” begin, see low and high cut-offs. The same lookup in inHg is on the 29.95 inHg page, and the unit itself is covered in what is inHg.

Quick answers

What is 1013 hPa in inHg?

29.91 inHg. The standard atmosphere, 1013.25 hPa, is 29.92 inHg. NOAA gives the standard sea-level pressure as 1013.25 in both millibars and hectopascals.

Is 1000 hPa high or low?

Low, mildly. It is 29.53 inHg, in the Low zone (995–1005 hPa). It is the kind of reading you see when a low-pressure system is nearby, but nothing about it is extreme.

How much hPa is low pressure?

There is no single value. Australia’s Bureau of Meteorology says that “there is no specific pressure value that automatically makes a system high or low”; what matters is the pressure relative to the surrounding area. On this site’s fixed bands, below 1005 hPa is Low and below 995 hPa is Very low.

What happens when pressure drops below 1000 mb?

It usually means a low-pressure system is close. The Met Office says low pressure generally brings unsettled weather; that is an association, not a guarantee. How windy it gets depends on how tightly packed the isobars are, not on the number alone. How fast the reading fell tells you more than where it landed (see below).

“High” and “low” are relative on a weather map

The common question — “is anything above 1013 high?” — mixes up two meanings. 1013.25 hPa is a reference value. A high or low on a weather chart is a region, defined relative to its surroundings. The Met Office puts it this way: standard sea-level pressure is 1013 hPa, but large areas of higher or lower pressure develop, “defined relative to their surroundings.”

The Bureau of Meteorology describes the number printed beside an H or L as the sea-level pressure at the centre, and gives one national service’s rough bands for a low’s centre: a shallow low is usually above 1000 hPa, a moderate low is 980–1000 hPa, and a deep low is below 980 hPa. It adds that a typical high often has a central pressure around 1020 hPa or higher. Those bands describe the centre of a system, not the reading where you stand: a 995 hPa reading at your house does not mean a moderate low is overhead. They also differ from this site’s fixed bands, which call 1005–1020 hPa Normal and start High at 1020. Both are conventions, and neither is wrong.

hPa and mb are the same number

1 hectopascal equals 1 millibar, so 1013 hPa and 1013 mb are the same reading (NOAA and the National Weather Service both state this). Only the name changed, when scientific units were standardized; meteorologists kept the familiar magnitude.

Station pressure vs. sea-level pressure

Every row above is a sea-level value. Pressure falls with elevation, so a device that shows raw station pressure will read lower than the weather report, and that gap is not a storm. The site’s ten-year reanalysis shows how big it can be:

• Denver (elevation 1,615 m): mean sea-level pressure 1014.8 hPa (29.97 inHg), mean station pressure 837.7 hPa (24.74 inHg) — about 177 hPa (5.23 inHg) lower.
• Miami (elevation 6 m): mean sea-level pressure 1017.1 hPa (30.03 inHg), mean station pressure 1016.4 hPa (30.01 inHg) — 0.7 hPa (0.02 inHg) apart.

So a reading near 838 hPa (24.75 inHg) in Denver is ordinary, and the same reading in Miami would be far outside anything in the record. When a number on a watch, phone or home barometer looks wildly low, check whether it has been set to sea level. Pressure at sea level explains the reduction and how to read a barometer covers setting one. Note that the reduction to sea level also inflates apparent variability at altitude, which matters for Denver in the next section.

Against these ten years of reanalysis, 1000 hPa is an uncommon sea-level reading in both cities, though far more so in one. Denver is below its 5th percentile, 1001.7 hPa (29.58 inHg), in 5% of hours, so 1000 hPa sits just past that line. Miami’s 5th percentile is 1011.5 hPa (29.87 inHg), and its lowest hourly value in the window was 988.3 hPa (29.18 inHg), so there 1000 hPa is well into the bottom tail. The city averages themselves sit in a narrow band: the 50 cities’ mean sea-level pressure runs from 1012.3 to 1018.5 hPa (29.89–30.08 inHg), so the typical local reading is in the low 1010s to about 1018, not exactly 1013.25.

How far a reading moves in a day

A single number matters less than how much it moves. The site counts a swing day as one with a 24-hour change of at least 6 hPa (0.18 inHg), and a big-swing day as one with at least 10 hPa (0.30 inHg); both are defined on /methodology. Across the 50 cities, the median is 180.7 swing days and 86.1 big-swing days per year.

The spread is the point. In Miami a 6 hPa day is rare; the median absolute 24-hour change there is 1.2 hPa (0.04 inHg). In Boston and Denver the median absolute change is 4.9 hPa (0.14 inHg), so half of all 24-hour changes there are at least that large — roughly one 5 hPa row of the table above. Boston’s largest 24-hour fall in the window, 51.5 hPa (1.52 inHg), is the largest of the 50 cities. The 6 hPa count saturates in volatile cities — Denver logs 281.6 swing days a year — so the 10 hPa column is the discriminating figure. All of these come from reanalysis, not station data, and the 2015–2024 window is too short for trend claims. Find the cities in the full set of 50, or check any US location.

Direction matters more than level

A steady 1000 hPa and a reading that fell from 1015 to 1000 overnight are different situations, although they share a row in the table. The site’s swing, big-swing and drop-day counts all measure that movement, not the level: a 15 hPa (0.44 inHg) fall inside 24 hours is a big-swing day wherever it starts. Falling and rising barometric pressure covers what a fall or a rise usually signals, how big a drop really is and how often US cities see one.

On the body: studies have found an association between pressure change and migraine onset in some people and none in others, and this page ties no particular reading, 1000 or 1013 hPa included, to symptoms — the research on headaches has the detail.

Pressure change is associated with symptoms in some people and not in others; effect sizes are modest and individual sensitivity varies widely. This page describes the weather, not you. It is not a prediction, not a diagnosis and not medical advice. If pressure-related symptoms are affecting your life, that is a conversation for a clinician.

Sources: NOAA JetStream, “Air Pressure” and the National Weather Service glossary (units and standard pressure); the UK Met Office and Australia’s Bureau of Meteorology (high and low pressure). City figures are Open-Meteo ERA5 hourly reanalysis, 2015–2024.

All 50 city pages · Check any US location · Methodology