# Is the barometric pressure inside my house the same as that outside **URL:** \ **Category:** Factual Questions\ **Created:** [April 8, 2017, 5:18am UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042 "2017-04-08T05:18:53Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 9, 2017, 2:25pm UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042/21 "2017-04-09T14:25:38Z")
Worth emphasising as **LSLGuy** mentioned, , if you know your current altitude you can trivially correct your offset from any meteorological station nearby. Although the change in pressure with altitude isn’t a linear function, within the first few thousand feet above sea level it is close enough to one inch of mercury per thousand feet that it is uncanny. (Or about 12 Pa per metre.) You are very unlikely to have a need (or have an instrument accurate enough) that the deviations from linear will matter to you. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [April 9, 2017, 2:34pm UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042/22 "2017-04-09T14:34:03Z")
> [@igor\_frankensteen](#): > > [snip] … If the OP is trying to monitor shifts, then it doesn’t matter how perfectly his watch barometer is calibrated. Not to mention, how accurate the watch barometer is designed to be, plays a part in what to do as well. If the barometer you are trying to calibrate isn’t all that sensitive and accurate to begin with, getting a precise calibration measurement isn’t really useful. Not to mention that traveling around might give crazy readings … especially in Western Colorado … altitude makes a huge difference … Consider Hurricane Tip and her central pressure of 25" of Hg … it was nearly a thousand miles to the closest place with “normal” pressure of 30" … Just three and a half miles up we’ll find 15" of Hg … ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [April 9, 2017, 2:58pm UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042/23 "2017-04-09T14:58:55Z")
> [@watchwolf49](#): > > 1 torr = 0.945 finkles per furlong per microfortnight per microfortnight What’s your point? Torr is a common unit still in use. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [April 9, 2017, 4:28pm UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042/24 "2017-04-09T16:28:06Z")
If the OP is using the watch for something like fitness tracking, then going to a weather service office would be overkill since it has to be re-calibrated every day at least. Also as igor frankensteen said, those are relative measurements not absolute. My cycling computer uses barometric pressure to measure altitude, and it’s accurate to within just a couple of feet. The thing is, when I calibrate it before each ride, I set the altitude in a location I know, not the barometric pressure, so the OP’s watch may be doing something different. Either way, because it’s so sensitive, changing weather patterns can shift the readings by several hundred feet over time, and I can see something like this being affected in an indoor closed environment. I’m not sure the pressure changes caused by things like exhaust fans or air conditioning would be a factor, but a sustained wind against the building, or the chimney effect of being in a high rise might. Either way, a slight elevation change can produce noticeable variances in readings, depending on how precise the measurements are anyway. ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [April 9, 2017, 4:43pm UTC](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042/25 "2017-04-09T16:43:37Z")
OP: look at a map of barometric pressures for your state, for example at: > **[Barometric Pressure Map for the United States](https://www.usairnet.com/weather/maps/current/barometric-pressure/)** > > Offering a Barometric Pressure Map for the United States Notice how slowly the pressure numbers change as you move 50 miles away (in contrast to temperature numbers for example). So just take the number from the closest quality weather station. [Previous page](https://boards.straightdope.com/t/is-the-barometric-pressure-inside-my-house-the-same-as-that-outside/784042.md?page=1)