These two get confused constantly, and mixing them up leads to a reading that does not fit.
Life Path Number: From Your Birth Date
Calculated from your date of birth, this number does not change and reflects the direction your life naturally leans toward: the lessons you keep encountering, and the traits you were born with.
Destiny Number: From Your Full Name
Calculated by converting the letters of your full birth name into numbers and reducing them, this number reflects what you are here to accomplish: the outward expression of your life, your reputation, and your work.
A Worked Example
Take someone with a Life Path 7, born to reflect and go deep alone, but a Destiny Number 3, built for public communication. On paper the two seem to pull in opposite directions. In practice this often shows up as someone who is genuinely private but ends up teaching, writing, or performing anyway, because the Destiny Number is what the world sees and rewards, even when the Life Path prefers solitude.
Why Both Matter Together
Read in isolation, either number gives a partial, sometimes contradictory picture. Read together, they usually explain a tension the person already feels but could not name.
A Quick Way To Tell Which One Someone Is Asking About
If the question is “why do I keep repeating this pattern,” that is a Life Path question. If the question is “why does my public reputation not match how I feel inside,” that is usually a Destiny Number question. A full reading looks at both, plus how they interact with your current Personal Year.