Choosing the right screw length and type is not depending on experience and trial and error anymore. There is now this app. The length is based on the thickness of the material and the type of connection. The choice for the the type of screw is depending on the base material and where the project will be used.
With this international app at hand, the choice becomes easy. Step by step you are guided through the selection process and given advice on the options.

Step 1. Choose the kind of project (indoor, outdoor, corrosive environment)

Step 2. Choose whether the connection will be an edged or face joint.

Step 3. Choose the type of wood, Hard or Soft wood.

Step 4. Provide the thickness of both sides of the connection (1/2" to 1 1/2")

Step 5. Your work is done, our turn. A overview of your choices and the advised option will be shown.