There are 3 Letters of Madd (also known as مَدْ تَبِيْعِي):

• Alif with a fatha before it ex. بَا
• Wow Sakin with Dhammah before it ex. بُوْ
• Yaa Sakin with Kasrah before it ex. بِيْ

These are stretched for two vowel counts.

Vowel counts: One vowel count is equivalent to the amount you would stretch a letter if it had one vowel (either fatha, dhammah or kasrah) on it.

Madd Fare’ee (مَدْ فَرعِي)
Letter of Madd followed by either hamza (ء) or sukun (ْ) fall under this category and come in four types:
• Madd Wajib Muttasil
• Madd Jaiz Munfasil
• Madd Laazim

Madd Wajib Muttasil

Hamzah (ء) after one of the letters of Madd in the same word
• Stretch for 4 or 5 vowel counts
• ex. جَاءَ

Madd Jaiz Munfasil

Hamzah (ء) after one of the letters of Madd in the next word

• Stretch 4-5 vowel counts
• ex. كَمَا اُمِرْت

Madd Laazim
Madd Laazim is that madd in which after a Letter of Madd comes a permanent sukun.
All are stretched for 6 vowel counts