The definition for the credit hour is provided on the Federal Register under Distance Education and Innovation.
Credit hour: Except as provided in 34 CFR 668.8(k) and (l), a credit hour is an amount of student work defined by an institution, as approved by the institution's accrediting agency or State approval agency, that is consistent with commonly accepted practice in postsecondary education and that—
(1) Reasonably approximates not less than—
(i) One hour of classroom or direct faculty instruction and a minimum of two hours of out-of-class student work each week for approximately fifteen weeks for one semester or trimester hour of credit, or ten to twelve weeks for one quarter hour of credit, or the equivalent amount of work over a different period of time; or
(ii) At least an equivalent amount of work as required in paragraph (1)(i) of this definition for other academic activities as established by the institution, including laboratory work, internships, practica, studio work, and other academic work leading to the award of credit hours; and
(2) Permits an institution, in determining the amount of work associated with a credit hour, to take into account a variety of delivery methods, measurements of student work, academic calendars, disciplines, and degree levels. (Federal Register, 2020)