How do I convert inHg to hPa (mb)?

Multiply by 33.8639. 30.00 inHg = 1015.9 hPa, 29.92 inHg = 1013.2 hPa and 29.50 inHg = 999.0 hPa. To go from hPa or mb to inHg, multiply by 0.029530 (or divide by 33.8639): 1000 mb = 29.53 inHg.

What is normal barometric pressure at sea level?

The standard atmosphere is 1013.25 hPa = 29.92 inHg = 760 mmHg = 101.325 kPa = 14.696 psi = 1 atm. Real sea-level pressure usually ranges from about 980 to 1040 hPa (28.9 to 30.7 inHg); hurricanes can drop below 920 hPa.

What is the difference between station pressure and sea-level pressure?

Station pressure is the actual absolute pressure at your location. Weather reports reduce it to sea level so maps at different elevations can be compared. In Denver (about 5,430 ft) a station pressure of 24.24 inHg corresponds to an altimeter setting of about 29.61 inHg. A barometer showing 24 inHg at altitude is not reporting a storm; it is reading station pressure.

What is the difference between altimeter setting and sea-level pressure?

Both are sea-level referenced. The altimeter setting (QNH) uses the standard atmosphere only, so it depends on station pressure and elevation. Meteorological sea-level pressure (SLP, QFF) also uses the air temperature, so on cold days at high stations it reads higher than the altimeter setting. At low elevations the two are almost identical.

How much does pressure drop with altitude?

Near sea level, about 1 inHg per 1,000 ft (roughly 1 hPa per 8 m, or 12 hPa per 100 m). The standard atmosphere gives 28.86 inHg at 1,000 ft, 24.90 inHg at 5,000 ft and 20.58 inHg at 10,000 ft.

What is the difference between hPa and mbar?

None in value: 1 hPa = 1 mbar = 100 Pa. hPa is the SI name used in meteorology; mb is the older name still used in many forecasts.

What unit do US weather stations use?

US surface reports and altimeter settings are in inches of mercury (inHg). Most other countries and aviation outside North America use hPa (mb).

Barometric Pressure Converter

1 inHg = 33.8639 hPa (mb); 1 hPa = 0.02953 inHg = 0.75006 mmHg; standard sea-level pressure is 29.92 inHg = 1013.25 hPa = 760 mmHg = 14.696 psi. A weather report gives pressure reduced to sea level; a barometer at elevation reads lower station pressure.

Enter Pressure

Input Unit

Pressure Value

Quick Presets

Station ↔ Sea-Level Pressure

Uses the pressure entered above.

The value above is

Elevation

Air temperature

Station pressure—

Altimeter setting (QNH)—

Sea-level pressure (temp.)—

Pressure altitude—

Converted Values

Enter a pressure value to see conversions

Common Pressure Reference Points

Condition	hPa	inHg	mmHg
Very high pressure	1040	30.71	780.1
Fair weather	1020	30.12	765.1
Standard atmosphere	1013.25	29.92	760.0
Changeable	1000	29.53	750.1
Stormy	980	28.94	735.1
Strong hurricane	940	27.76	705.1

Station pressure by elevation (standard atmosphere)

What a barometer reads at each elevation when sea-level pressure is 1013.25 hPa / 29.92 inHg and the air follows the ICAO standard atmosphere.

Elevation	Metres	hPa (mb)	inHg	kPa	psi
0 ft	0	1,013.3	29.92	101.33	14.70
500 ft	152	995.1	29.38	99.51	14.43
1,000 ft	305	977.2	28.86	97.72	14.17
2,000 ft	610	942.1	27.82	94.21	13.66
3,000 ft	914	908.1	26.82	90.81	13.17
4,000 ft	1,219	875.1	25.84	87.51	12.69
5,000 ft	1,524	843.1	24.90	84.31	12.23
6,000 ft	1,829	812.0	23.98	81.20	11.78
8,000 ft	2,438	752.6	22.22	75.26	10.92
10,000 ft	3,048	696.8	20.58	69.68	10.11
12,000 ft	3,658	644.4	19.03	64.44	9.35
14,000 ft	4,267	595.2	17.58	59.52	8.63
18,000 ft	5,486	506.0	14.94	50.60	7.34
29,032 ft (Everest)	8,849	314.4	9.28	31.44	4.56

Worked examples

Station to altimeter setting. Denver, elevation 5,431 ft (1,655 m), station pressure 24.24 inHg (820.9 hPa): A = (820.9 − 0.3) × [1 + 8.422×10⁻⁵ × 1,655 ÷ 820.6^0.190284]^5.2553 = 1002.7 hPa = 29.61 inHg. Pressure altitude is about 5,710 ft.

Altimeter setting to station pressure. An airport at 1,000 ft reports 29.92 inHg. Station pressure = (1013.25^0.190284 − 8.422×10⁻⁵ × 304.8)^5.2553 + 0.3 = 977.4 hPa = 28.86 inHg, the value a correct absolute barometer there should show.

Unit conversion. 1000 mb × 0.029530 = 29.53 inHg; 30.10 inHg × 33.8639 = 1019.3 hPa = 764.5 mmHg = 14.78 psi.

Sources: NWS altimeter setting formula · NWS pressure conversions · NIST SP 811

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Summary

This converter changes barometric pressure between inches of mercury (inHg), hectopascals (hPa), millibars (mb), millimeters of mercury (mmHg), kilopascals (kPa), pounds per square inch (psi) and standard atmospheres (atm) using exact factors. It also bridges the two kinds of pressure people mix up: station pressure, the absolute pressure a barometer measures where it sits, and the sea-level values in weather reports. Enter your elevation to turn a station reading into an altimeter setting (the NWS/ICAO standard-atmosphere formula) and a temperature-corrected sea-level pressure, or turn a reported altimeter setting back into the pressure at your location, with the pressure altitude.

How it works

Pick the unit of your reading and type the value; all seven units update instantly.
Factors: 1 inHg = 33.8639 hPa (mercury at 0 °C), 1 mmHg = 1.333224 hPa, 1 psi = 68.9476 hPa, 1 atm = 1013.25 hPa, 1 kPa = 10 hPa, 1 hPa = 1 mb.
To convert station pressure to an altimeter setting, the tool uses the NWS formula: A = (P − 0.3) × [1 + (1013.25^0.190284 × 0.0065 ÷ 288) × H ÷ (P − 0.3)^0.190284]^(1/0.190284), P in hPa, H = elevation in metres.
Sea-level pressure adds the station temperature: SLP = P × (1 + 0.0065 H ÷ T)^5.2559, T in kelvin, assuming the standard 6.5 °C/km lapse rate.
Pressure altitude = 145,366 × [1 − (P ÷ 1013.25)^0.190284] feet.

Use cases

Convert a weather report in inHg to hPa or mb, or the reverse.
Find the station pressure at your elevation from the airport altimeter setting, for example to calibrate a barometer or a weather station.
Convert a home weather station's absolute (station) pressure to the relative sea-level value shown in forecasts.
Get pressure altitude for aircraft performance and density altitude calculations.
Convert lab or HVAC readings between kPa, psi, mmHg and atm.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu