From H. W. Smyth, Greek Grammar, I §§149-188
GENERAL PRINCIPLES, ANASTROPHE, CHANGE OF ACCENT IN DECLENSION, INFLECTION AND COMPOSITION, PROCLITICS, ENCLITICS
164. The penult, if accented and long, takes the circumflex when the ultima is short by nature (νῆσος, ταῦτα). In all other cases it has the acute (φόβος, λελυκότος, τούτου).
a. Apparent exceptions are ὥστε, οὔτις, ἥδε (properly ἧδε).
b. A final syllable containing a vowel short by nature followed by ξ or ψ does not permit the acute to stand on the antepenult (οἰκοφύλαξ); but the circumflex may stand on the penult (κῆρυξ).
165. The ultima, if accented and short, has the acute (ποταμός); if accented and long, has either the acute (λελυκώς), or the circumflex (Περικλῆς).
166. When the ultima is long, the acute cannot stand on the antepenult, nor the circumflex on the penult. Thus, ἄνθρωπου and δῶρου are impossible.
167. When the ultima is short, a word, if accented
a. on the ultima, has the acute: σοφός.
b. on a short penult, has the acute: νόμος.
c. on a long penult, has the circumflex: δῶρον.
d. on the antepenult, has the acute: ἄνθρωπος.
168. When the ultima is long, a word, if accented
a. on the ultima, has the acute or the circumflex: ἐγώ, σοφῶς.
b. on the penult, has the acute: λέων, δαίμων.
Reference address : https://www.ellopos.net/elpenor/lessons/greek-accentuation.asp?pg=4