Medford Clock & Barometer

Altitude Correction Chart


Remember that all barometers are altimeters. The elevation where you live will affect the reading on your instrument. The local news channel will always report pressure at sea level so depending on your elevation your instrument may or may not match this number. The reading can be adjusted to display " local " pressure or " sea level " pressure on aneroid barometers, and even on wheel, or banjo barometers, but not on any sticks or fortin types. These instruments are going to give the true " local " pressure where the instrument is located, or the reading is being taken. One point to understand though, is that in most cases, the pressure reading is incedental. You can look around and see what the weather is at present, your main concern is whether the pressure is rising, falling, or holding steady, indicating better, poorer, or stable weather is on the way.

If your instrument displays millimeters or millibars, these numbers can be converted to inches using a calculator.

1 inch = 25.4 mm
1 inch = 33.864 mb.

Altitude correction chart
Feet above sea level Inches to add to reading
50 0.06
100 0.12
150 0.17
200 0.22
250 0.27
300 0.33
350 0.38
400 0.43
450 0.48
500 0.54
550 0.59
600 0.64
650 0.69
700 0.74
750 0.79
800 0.84
850 0.89
900 0.94
950 0.99
1000 1.04

Medford Clock & Barometer, 3 Union Street, Medford, NJ 08055
Phone: (609) 953-0014, Fax (609) 953-0411
E-mail: jim@medfordclock.com
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