Tip#17: The Right Form Length
You might be wondering how much or how little information you should require with a form. There is no magic answer when it comes to how many fields your form should contain but the best balance would be to collect only the information you really need.
The fewer fields you have in a form, the more likely you will receive more conversions. This is because with each new field you add to a form, it creates friction (more work for the visitor) and
fewer conversions. A longer form looks like more work and sometimes it will be avoided all together. But on the other hand, the more fields you require, the better quality those leads might be. The best way to determine what works best is to test it.