First order RC filters are very useful and ubiquitous filters in the industry. From simple filtering jobs, integration, anti-aliasing filters they are used almost without thinking. There is a low frequency point on the characteristic ( say fl ) and a high frequency point ( say fh ). The low frequency point is the so-called 3 dB point on the first order characteristic and the high frequency point is where the high attenuation occurs. For further details, interested readers are directed to the Signal Processing Group Inc. website. Please look at the “complementary items” menu and follow to the “more free reports and articles ” link. Select the ” First order filter attenuation and frequency parameter calculations algorithms” item. This post deals with the availability of a javascript calculator released for calculating the filter characteristic points. Please select the calculators link from the SPG website and then select the calculator item from the index of calculators.