How do I know if ED has a D or T sound in the pronunciation of words that end with ed?

See a translation

It depends on the sound before -ed. If the sound is voiced (for example: g, l, dg, m, z, r, or any vowel), then it's pronounced with a 'd' sound. If the last sound before -ed is voiceless (for example: k, p, s, ch), then -ed is pronounced as 't.'

If the word ends in 't' or 'd,' the 'e' in -ed is also pronounced.

How do you know whether a sound is 'voiced' or 'voiceless?'

Put your hand on your throat when you say the sound. If you can feel a strong vibration, then its voiced, and you should say 'd.' If you don't feel any vibration, then its voiced and you should say 't.' And again, if the last sound is 't' or 'd,' pronounce -ed as 'id.' (it sounds like the 'id' in 'idiot.')

Some examples:

'look' ends in a voiceless sound 'k,' so 'looked' is pronounced 'lookt.'

'seem' ends in a voiced sound 'm,' so 'seemed' is pronounced 'seemd.'

'end' ends in 'd,' so 'ended' is pronounced 'endid.'

'hate' ends in 't,' so 'hated' is pronounced 'hatid.' (in American and Canadian English we pronounce this more like 'hadid')

Also, you shouldn't trust the spelling of a word. Just because 'hate' ends with an 'e' doesn't mean that the 'e' is pronounced, so say the word out loud to decide what sound it ends with.

(Sorry if this answer is long or difficult to read, but it's a hard concept to explain).