Adobe Illustrator, a vector graphics creation and editing program, natively saves files in the ".AI" format. Most fonts for your computer are saved in ".TTF" (True Type Font) format, which requires a special font-editing program to open and edit. If you create images or letters in Adobe Illustrator that you want to convert into a TTF file so you can use them in other programs as a font, the best method is to install a font-editing program that can import AI files.
Download and install the free trial of a font-editing software program that can import AI files, like FontLab Studio, FontCreator or AsiaFont Studio.
Go to "File > Import" and select your AI file(s). Click "Open." Depending on how you saved your letters or images, you may need to import each image as a separate character or import one large image and splice it into separate characters.
Go to "File > Save As" and save your new font in TTF format.