On the left is Immortal Beast's Rank while on the left is Human Cultivation Stage Equivalent.

Mortal Cultivation =

Earth Rank = Body Transformation Stage 

Sky Rank = Qi Gathering Stage

Star Rank = Qi Condensation Stage

Spirit Rank = Core Formation Stage

Mystical Rank = Golden Core Stage

Sovereign Rank = Nascent Soul Stage

Half Immortal Cultivation =

Celestial Rank(Early, Middle, Late) = Infant Soul Stage, Void Refining, Soul Severing

Transcendent Rank (Early, Middle, Late) = Soul Unity Stage, Transcending Tribulation Stage, Great Ascension Stage.

Divine Emperor/Empress Rank (Early, Middle, Late) = Quasi Immortal, Half Immortal.

True Immortal Cultivation = Coming Soon!