• Barometers are typically calibrated for MSLP (mean sea level pressure) using an adjustment screw on the barometer and set to match an official weather service barometer reading.
• Services that list localized barometric pressure may include weather reports from tv, radio, local news, airports, or the internet e.g. Met-Office or Yahoo Weather that will display the barometric pressure for your area with a time stamp.
• Barometers may also require calibrating, taking into account temperature and/or altitude e.g. adjustments are common if you live at an elevation greater than 305m /1,000 feet.
• Barometers should only be calibrated during a period of fair weather, not during stormy weather.
• Read the instructions accompanying your barometer for correct usage.
• Confirm accuracy of your unit by periodically comparing readings to other reliable sources e.g. weather office reports.

Why are Barometers Calibrated?

Barometers are usually calibrated by the user in order to ‘standardize’ their equipment. This means that barometers are set at home to match/correlate with local weather reports from authoritative sources e.g. Metereological Office. Pressure readings given in weather reports are adjusted to pressure at sea level (mean sea level pressure  or MSLP). Therefore, your barometer will be calibrated to measure pressure at sea level and not the actual local atmospheric pressure. The reason for doing this is so that all locations can be compared independent of the altitude at each location i.e. high pressure and low pressure are not dependent on geographical location. This makes the isobars (a line connecting points of equal atmospheric pressure) of weather maps a meaningful and useful tool.