Perfect fourth

In just intonation, pitches a fourth apart have a 3:4 (“three-to-four") frequency ratio. If one pitch is at 300 Hz, a pitch a fourth higher is at 400 Hz. A pitch a just fourth lower is at 225 Hz.

In 12 tone equal temperament, pitches a fourth apart have a difference of 500 centsA cent is a unit of measurement for intervals and is defined as 1/1200th of an octave.Visit the link to learn more. If one pitch is at 300 Hz, a pitch a fourth higher is at 400.452 Hz. A pitch a fourth lower is at 224.746 Hz.

Context

A Guide to the Maqam Tuning Presets for Ableton Live 12, Introduction to European historical tunings and temperaments, 12 Quintal (center C), 12 Tertial Dflat-Fsharp (center C)