These are useful tools to have or your workbench, installed on your computer, or bookmarked on your browser:

Resistor Value and Ratio Calculator

Sometimes we need a resistor value more precise than what is offered in the standard series. For this task, use the Resistor Value Calculator.

A more complicated task is to pick resistors to satisfy a ratio. This is often done to set the division ratio in a voltage divider, for example. This is where the Resistor Ratio Calculator comes in handy.

Unit Conversions

There are many good online unit converters. None include decibel conversions. Here are two that will cover most of your needs:

Op-Amp Filter Design

Most of the ic fabricators have comprehensive online parts selectors and circuit designers:


Along with many other useful tutorials is one on bandpass filters:

HTML Color Codes

Includes a color picker with hex and RGB values.

Stripboard Design

Stripboards, also known as Veroboards, are great for rapid prototype development. Parts density is less than that of printed circuit board design but that means if you can fit your circuit on a stripboard it will certainly fit on a PCB of similar or slightly smaller dimensions. In the prototype stage there is a larger scope for moving parts or changing connections than with PCBs.

Most of the freeware designers have antiquated or quirky user interfaces and many are no longer supported. The best is VeroDes. Others are reviewed at:


If you become a stripboard fan Lochmaster from Abacom is essential. It is easy to use, comes with a large parts library, and allows creating your own custom components and boards. It costs €50 but you do not have to pay VAT if you live outside the EU.

You will also need an inexpensive swivel-head pin vise and a 3mm or 7/64-inch bit to cut the traces.

Stripboard parts side

Stripboard parts side

Stripboard trace side

Stripboard trace side