What's the best way to convert AVI to MP4?

I've got lots of videos on my computer, and most of them are AVI format that is not supported by iPhone. How can i convert AVI to MP4 effortlessly?

http://www.freemake.com

This will do what you want, you can batch add them and it will convert them

Handbrake - it's completely free and has presets for various phone and tablet file types / resolutions.

(It will also work with DVDs, Blu-ray etc.).

https://handbrake.fr/

Why would you move videos from computer to iphone, videos take up a ton of space.

WinX HD Video Converter Deluxe. This software can convert all the video formats as long as you can find, AVI and MP4 included, of course. The speed is really fast. The lastest version of this converter is added two hardware acceleration options. Either of them reduces the time spent on conversion big time.