This app prompts the user the user for Amax (p-p maximum variation in the pass band) in dB, Amin (minimum response attenuation), Wc (upper edge of the pass band) in rad/sec and Ws (upper edge of stop band). After hitting the Calculate button, the values for Epsilon, e, and the Order of the filter, n, are returned. For example, enter 0.1 for Amax, 60 for Amin, 250 for Wc and 2000 for Ws, hit "Calculate" and your results should be Epsilon e = 0.15262 and Order n = 3.42.

Compare this with the Butterworth filter...