Leavitt also developed a standard of photographic measurements that was accepted by the International Committee on Photographic Magnitudes in 1913, and called the Harvard Standard. To do this she used 299 plates from 13 telescopes and used logarithmic equations to order stars over 17 magnitudes of brightness. She continued refining and enlarging upon this work throughout her life.

Leavitt was not employed to pursue her own topics of study, but to research what the head of the observatory assigned. Because of the prejudices of the day, she didn't have the opportunity to use her intellect to the fullest, but a colleague remembered her as "possessing the best mind at the Observatory," and a modern astronomer calls her "the most brilliant woman at Harvard." She worked at the Harvard College Observatory until her death from cancer in 1921.