A name's Heart Number (also called the Heart's Desire or Soul Urge number) is calculated from the vowels only. Where the Personality Number describes how a person appears to others, the Heart Number describes what actually motivates them underneath: the private wants and values that drive their choices even when no one else can see them. Vowels are considered the "soul" of a name in Pythagorean numerology, carried through in speech even when consonants are dropped or mumbled.

A Heart Number of 9 points to an inner drive to contribute to something larger than themselves. Underneath whatever this person shows the world, what they privately want most is to matter to people beyond their immediate circle, a genuinely humanitarian impulse.