Chess.com rating

Grateful if someone could explain the Chess.com ratings. A recent game was drawn after 70 moves. This was one of my better games and yet my rating did not change. In an intriguing game I recently won, my rating improved by 4 points. I have just won a game on time after 4 moves and yet my rating has increased by 9 points!!!

It depends on:

1)What your Glicko RD is

2)What your opponent's Glicko RD is

3)What ratings the players have on that time control

Ratings calculations have nothing to do with how well or how long you played. It is based only on the result of the game: win, lose, or draw.

If you win, your rating will increase. If you lose, it will decrease. How much it does so has mostly to do with the difference in your ratings. When you draw, you'll get a few points if your opponent is rated higher than you are.

On top of this, your rating is more volatile when you first start out -- the amount you earn or lose will be greater -- but this smooths out over time.

Thanks for the explanations although don't know what a Glicko RD is. Still confused how you can gain so many points when you 'win' on time with only a few moves played.

Because a win is a win as far as ratings go. If your opponent resigns on move one, it's no different than you grinding out a 100-move win.