inHg to mb converter
1 inHg is 33.86389 millibars: turn an altimeter setting, a US weather report or a manometer reading in inches of mercury into the millibars used on METAR remarks, European weather charts and barograph logs. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Inhg
- 1
- Result
- 33.86389 mb
- Converted
- 33.86389
- Mb
- 33.86389
- Mbar
- 33.86389
An inches-of-mercury to millibars converter turns a mercury-column or aviation altimeter pressure reading into the millibar (hectopascal-scale) value used on METAR remarks, European weather charts, barograph logs, and many HVAC or process sheets that quote mbar instead of inHg.
Why inches of mercury and millibars still meet at an exact factor
Inches of mercury remain the everyday column-height and altimeter-setting unit across North American aviation, many US weather broadcasts, and industrial vacuum or manometer sheets that still quote inHg side by side with psi. Millibars—numerically identical to hectopascals—belong to the SI-adjacent weather and marine family used on METAR QNH fields in many regions, European surface charts, scientific barographs, and process documentation that fixed one hundred pascals as one millibar.
The bridge between them is not a memorised survey rule of thumb: by the conventional definition used across KIT pressure caps, one inch of mercury equals exactly three thousand three hundred eighty-six point three eight nine pascals, and one millibar equals exactly one hundred pascals, so one inch of mercury equals exactly thirty-three point eight six three eight nine millibars. That makes the conversion a single exact multiplication, millibars equals inches of mercury times thirty-three point eight six three eight nine.
Teachers sometimes still teach multiply by about thirty-four with intermediate rounding, but truncating too early drifts on multi-atmosphere compressor stages or long altimeter-setting chains. Practically, about twenty-nine point nine two inHg near one standard atmosphere is the identity check many pilots and meteorologists learn first, and this tool preserves that conventional scale after fixed twelve-decimal rounding.
Practical tips, checks, and related searches
Round-trip sanity checks are easy: convert one inHg and confirm you receive exactly thirty-three point eight six three eight nine millibars after rounding, or convert two inHg and confirm the result is twice that factor within the same twelve-decimal policy. When teaching, pair the exact path with the mental shortcut of about thirty-four so students see that the identity case is preserved without intermediate truncation. Stay inside the absolute range so the multiply cannot overflow into a non-finite result the solver must reject.
This landing targets people searching for inHg to mb, convert inches of mercury to millibars, or an exact inHg pressure calculator; it is not a general multi-unit pressure hub, not an mb-to-inHg primary form, not an ICAO pressure-altitude solver, and not a blood-pressure category tool. Prefer this capability when the input is already in inches of mercury and you only need millibars; if you must convert among many pressure units or altitude in one call, use a broader pressure or pressure-altitude converter instead.
Document the factor one inch of mercury equals thirty-three point eight six three eight nine millibars in lab notebooks so graders can reproduce the same arithmetic without depending on a rounded table snippet from an older textbook appendix.
What you can do with it
Aviation altimeter and METAR bridging
Turn US-style altimeter settings in inHg into millibar (hPa-scale) fields for international flight planning and METAR QNH comparisons.
Weather and barograph logs
Map inches-of-mercury station readings into millibar columns on European charts and scientific barograph exports without survey rounding.
Teaching and worksheet checks
Students convert classroom inHg readings to millibars and compare hand work against deterministic steps before submitting lab reports.
FAQ
Is 33.86389 mbar per inHg exact?
Yes for this converter. It hard-codes 3386.389 Pa per inHg (the same factor as the pressure-altitude capability) divided by 100 Pa per mbar, rather than a looser survey approximation such as multiply by about thirty-four.
What input field do I send?
Send a finite number in the field inhg.
Is the inHg to mb converter free?
The browser tool is free and runs locally.
Are millibars the same as hectopascals?
Yes, they are numerically identical: one millibar is 100 pascals, which is one hectopascal. A result of 33.86389 millibars can be read directly as 33.86389 hPa on a weather chart.
Why not just multiply inches of mercury by 34?
Multiplying by about 34 is fine as a mental check, but rounding that early drifts across multi-stage compressor sheets or long altimeter-setting chains. The exact 33.86389 keeps every step consistent.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/conv/inhg-to-mb \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"inhg":29.9213}'const res = await fetch("https://api.kit.forhosting.com/conv/inhg-to-mb", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"inhg": 29.9213
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/inhg-to-mb",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"inhg": 29.9213
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/inhg-to-mb", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"inhg":29.9213}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"inhg":29.9213}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/inhg-to-mb", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"inhg": 29.9213
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.inhg_to_mb",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Invalid or missing input fails with a clear invalid_input error instead of inventing a number.
How to call the API and what comes back
Absolute values must stay within the published limit of one trillion. Prefer bare numbers when you control the client; string numbers are accepted only when they match a strict finite numeric pattern without units, thousand separators, or currency symbols embedded in the field. Send a JSON body with one required finite number field named inhg. Aliases inHg, in_hg, inches_hg, value, pressure, and inhg_value are accepted so SDK clients and form posts can use the name that fits the product. On success the response echoes rounded inhg, sets mb, mbar, result, and converted to the same rounded millibar magnitude, unit to the token mb, from_unit to inHg and to_unit to mb, factor and mbar_per_inhg to the rounded exact conversion factor thirty-three point eight six three eight nine, pa_per_inhg to three thousand three hundred eighty-six point three eight nine, formula to a short English equation string, message to a brief summary, and steps to an ordered array of substitution lines. Failed validation—missing fields, non-finite numbers, bare plus or minus signs, non-numeric strings, values outside absolute limits, or a non-finite converted result—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item.
Practical tips, checks, and related searches
Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately omit inhg or pass text.
Technical questions
What factor converts inHg to mb?
By the conventional definition used in KIT pressure caps, one inch of mercury equals exactly 3386.389 pascals and one millibar equals 100 pascals, so 1 inHg = 33.86389 mbar. The tool computes mb = inHg × 33.86389 and rounds to twelve decimal places for stable JSON.
What happens on invalid input?
Missing fields, non-finite numbers, or values outside the absolute limit return invalid_input. Failed tasks are never charged.