Tidal range is the difference between an area's high tide and an area's low tide. Tidal range allows people to determine how much the tides vary over the course of one cycle each day. Tidal ranges affect earth science concepts, such as erosion of the coast.
Find the low tide for the day. Tide data is found from several sources. Usually local stations with a weather program will have tidal data. In addition, NOAA keeps track of tidal data. For example, low tide at one beach was 1 foot.
Find the high tide for the day. Use the same source so you eliminate a chance of differing data sets. In our example, high tide was 3 feet.
Subtract the low tide from the high tide to determine tidal range. In this example, 3 feet minus 1 foot equals a tidal range of 2 feet.