The final ed forms the past tense of regular verbs (such as needed and worked) and of some adjectives (such as interested and tired). The ed can cause problems for some non-native speakers because it can be pronounced in three different ways: as /Id/, /d/, or /t/. Here are the three rules you need to know when pronouncing -ed.

Rule 1
If the last letter of the word is spelled with a d or a t, the ed is pronounced as /Id/ and as a separate syllable.
needed, avoided, admitted, separated, attended, visited, decided, waited

Rule 2
If the last letter of the word ends in a voiced consonant or a vowel sound, the e is silent and d is pronounced as /d/. (Reminder: Voiced consonants are /b/, /d/, /g/, /v/, /m/, /n/, / r/, /l/, /z/, /ʤ/, /y/, and /ð/.)
opened, called, changed, closed, earned, loved, pulled, showed

Rule 3
If the last letter of the word ends in a voiceless consonant, the e is silent and the d is pronounced as /t/. (Reminder: Voiceless consonants are /p/, /t/, / k/, /f/, /s/, /ʃ/, /tʃ/, and /θ/.)
passed, washed, helped, watched, laughed, worked, stopped, liked