There are 3 ways to pronounce the final -ed in a word.
-ed = /id/
-ed = /d/
-ed = /t/
How do you know which sound goes with which word? Look at these verbs:
Which sound goes with which word?
Here are the rules...
If the last sound of the word is unvoiced* (uses no only air to make the sound) except t, the -ed will sound like /t/.
Look at the words kiss and hope. The last sound of kiss is /s/. It doesn't use the voice to make the sound. So the -ed will not use a voice to make a sound either. The word sounds like /kist/. The word hope ends with /p/. It doesn't use the voice so /t/ is at the end. It sounds like /hopt/.
If the last sound of the word is voiced* (uses some noise to make the sound) except d, the -ed will sound like /d/.
Look at the words learned and played. The last sound of learn is /n/. It uses the voice. The -ed will also have a voice sound like /d/. So learned sounds like /lernd/. Play also has a voiced sound at the end. Played is pronounced /pleid/.
If the last sound to the word is /d/ or /t/, the -ed will sound like /id/.
Look at the words wanted and mended. They end with a /t/ or /d/. Wanted sounds like /wantid/ and mended sounds like /mendid/.
Note: Don't think about the spelling, only think about the final sound. For example, cough sounds like /kaf/. /f/ is unvoiced. Coughed is /kaft/.
*If you are not sure if a sound is voiced or unvoiced, put your hand on your throat when you say the sound. If it is voiced, you will feel a vibration, or movement, in your throat. If it is unvoiced, you will feel nothing in your throat.