555Calc 1.0 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The software lies within Office Tools, more precisely Calculators. The most popular version of the 555Calc is 1.0. The actual developer of the free software is 555Calc. We recommend checking the downloaded files with any free antivirus.
From the developer:
A simple calculator to help choosing resistor and capacitor values to get the frequency you're looking for on a 555 timer. The Frequency text is in scientific notation and often has so many decimal places that it cuts off the power so it's difficult to know whether 4.2 is 42 or 4.2 or 4200 Hz.
You may want to check out more software, such as OC Conversion Pro, Construction Master Pro or Skalc, which might be similar to 555Calc.