This converter turns inches of mercury into millibars instantly, using the exact factor 1 inch of mercury = 33.86389 millibars. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
US aviation and weather altimeter setting unit. The meteorologist’s unit — sea-level pressure averages 1013.25 mbar.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
inches of mercury- The amount you are converting, measured in inches of mercury
33.86389- The exact number of millibars in one inch of mercury
millibars- The converted result
How it works, step by step
- Enter the number of inches of mercury you want to convert.
- The value is multiplied by 33.86389, the exact conversion factor.
- The result is displayed in millibars, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 inches of mercury
Multiply 5 by 33.86389. That gives 169.3194 millibars. A quick sanity check: one inch of mercury is larger than one millibar, so the number should get bigger — and it does.
Converting 72 inches of mercury
72 × 33.86389 = 2,438.2 millibars. Working backwards, 2,438.2 ÷ 33.86389 returns 72 inches of mercury, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many millibars are in one inch of mercury?
Exactly 33.86389. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert inches of mercury to millibars?
Millibars = inches of mercury × 33.86389. To reverse it, divide instead: inches of mercury = millibars ÷ 33.86389, which is the same as multiplying by 0.02952998016.
Is the inch of mercury bigger than the millibar?
Yes. One inch of mercury equals 33.8639 millibars, so it is the larger unit.
Why does my answer differ slightly from other inhg to millibar converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a inch of mercury?
US aviation and weather altimeter setting unit.
What is a millibar?
The meteorologist’s unit — sea-level pressure averages 1013.25 mbar.
Inches Of Mercury to millibars reference table
| Inches Of Mercury | Millibars |
|---|---|
| 0.5 inHg | 16.9319 mbar |
| 1 inHg | 33.8639 mbar |
| 2 inHg | 67.7278 mbar |
| 3 inHg | 101.5917 mbar |
| 5 inHg | 169.3194 mbar |
| 10 inHg | 338.6389 mbar |
| 15 inHg | 507.9583 mbar |
| 20 inHg | 677.2778 mbar |
| 25 inHg | 846.5972 mbar |
| 50 inHg | 1,693.19 mbar |
| 75 inHg | 2,539.79 mbar |
| 100 inHg | 3,386.39 mbar |
| 250 inHg | 8,465.97 mbar |
| 500 inHg | 16,931.94 mbar |
| 1000 inHg | 33,863.89 mbar |
Exact factor: 1 inch of mercury = 33.86389 millibars. Values rounded for display.