WebToolArcPractical guide and verification
Distinguish station pressure from sea-level pressure
Station pressure is the pressure measured at the station elevation. Sea-level pressure is a reduced value intended to make observations at different elevations more comparable. Do not substitute one for the other in a workflow that explicitly requires the measured station value.
Elevation and temperature drive the reduction model
Reducing pressure to sea level requires assumptions about the vertical atmosphere, not just an altitude subtraction. Temperature and the chosen model can materially change the result, especially at higher elevations. Keep the model inputs with the reported pressure.
Keep pressure and elevation units consistent
hPa, kPa, Pa, inHg and mmHg represent the same physical quantity at different scales, while elevation may be entered in meters or feet. Verify conversions before comparing the result with a weather station or aviation source.
Weather-service reductions may use more detailed methods
Operational meteorological networks can use virtual temperature, humidity history or station-specific procedures. A browser calculator is useful for a transparent approximation and unit conversion, but it may not reproduce an official reported SLP exactly.
Use a round trip as an arithmetic check
If the tool supports both station-to-sea-level and reverse calculation, convert a value and then solve back using the same elevation, temperature and model. The recovered station pressure should agree within rounding; a large difference usually points to a unit or input mismatch.