user3237: 
In blitz, the knight is stronger than the bishop. - Vlastmil Hort

I am using this point value system for classical time controls (at least one hour per player):

Pawn = 1
Knight = 3.25
Bishop = 3.25
Rook = 5
Queen = 9.5
Bishop pair = +0.5

But as we all know, the Knight gets a little bit stronger in Rapid (from 15 minutes to 60 minutes per player), and it perhaps gets even more powerful in Blitz (from 3 minutes to 15 minutes per player). I would like to quantify/evaluate the average strength of the Knight in Rapid and in Blitz.
Therefore my two questions are:

How many centipawns does the Knight gain in Rapid?
How many centipawns does the Knight gain in Blitz?

Even though it may not be easy, please try to make estimations as precise as possible.
.
.
@Wes : Well I have at least three sources that confirm that Knights get stronger in Rapid and Blitz.
The first is GM Vlastmil Hort which I previously quoted. He had a peak rating of 2620 Elo and even reached the 1977–78 Candidates Tournament.
The second is this news report from Chess.com about a "death match" which happened only a week ago.

"Before the match, I thought it was easier to play in blitz with the knight, not the bishop," GM Kosintseva said, reflecting the popular notion that knights can be very tricky with minimal time.

The third source is this Chess.com thread, where a National Master said:

It does matter and knights are better in blitz !  Take it from someone who has played more than 50,000 blitz games ! Most titled players I talk about this with agree that knights are better in blitz than bishops.


user2180: The Knight is not stronger in blitz, such a statement is nonsense.
It is you that are weaker at calculating at blitz, and the Knight is simply more difficult to handle with less time to calculate due to the kind of moves you can make with it.
So it's matter of how your brain handles Knights nothing intrinsic in the Knight.

user3890: I have no mathematical formula to calculate the value of a knight or bishop depending on the time control (which is a related question and was asked here), but as I am mainly a Chess.com user and thus play blitz and rapid on the internet, I'll try to make an educated guess. My answer will be based on chess played with a mouse, not OTB.
There are several factors while considering the numerical value of the knight and the bishop that have to be taken into account.
1.1. The bishop is a long range piece, and this means that you have to make longer moves when moving it and consider more squares it can attack and defend.
1.2. The knight is a short range piece, and thus you only have to care about a smaller part of the board when moving it.
2.1. The bishop can only control half the board, and thus your opponent may easily avoid it by simply placing his pieces on the opposite color.
2.2. The knight, albeit slower, can control the whole board, this means that your opponent's king is not safe of checks anywhere, and checks are quite time consuming (at least from a couple to a handful of seconds).
3.1. The bishop moves (diagonally) are very predictable.
3.2. The knight moves (L shape and able to jump over pieces) are hard to predict, and it's easy to blunder forks when one is hopping around you.
The references to time consuming moves may look quite odd to players that do not use the internet. However, they do play an important role, since the time control is so reduced that almost instant answers are needed in the endgame, and these cannot be easily reached by long-range pieces.
There may be more, but I consider these points, specially the last one, the most important. If we consider the pros and cons, clearly the surprise factor of the knight and the fact that he is more consuming to your opponent than the bishop, give him the upper hand. By experience, I have lost many games and draw winning positions being low on time and blundering a fork to a knight, and also spent a few extra seconds on the clock due to an unexpected check and ended up losing on time.
This is why I consider the knight to be at least 4.00 pawns, while the bishop keeps his 3.25 pawns. However, in some positions (all the pawns in one side, or all the pawns blocked, or the enemy king cut off, or similar positions where the knight can easily outmaneuver the bishop) I would give the knight a full pawn advantage at 4.25 pawns.
I am well aware that this answer is completely subjective, but as said, I couldn't find a way to quantify these advantages.

3237: <blockquote>
  <p>In blitz, the knight is stronger than the bishop. - Vlastmil Hort</p>
</blockquote>

<p>I am using this point value system for classical time controls (at least one hour per player):</p>

<ul>
<li>Pawn = 1</li>
<li>Knight = 3.25</li>
<li>Bishop = 3.25</li>
<li>Rook = 5</li>
<li>Queen = 9.5</li>
<li>Bishop pair = +0.5</li>
</ul>

<p>But as we all know, the Knight gets a little bit stronger in Rapid (from 15 minutes to 60 minutes per player), and it perhaps gets even more powerful in Blitz (from 3 minutes to 15 minutes per player). I would like to quantify/evaluate the average strength of the Knight in Rapid and in Blitz.</p>

<p>Therefore my two questions are:</p>

<ul>
<li>How many centipawns does the Knight gain in Rapid?</li>
<li>How many centipawns does the Knight gain in Blitz?</li>
</ul>

<p>Even though it may not be easy, please try to make estimations as precise as possible.</p>

<p>.</p>

<p>.</p>

<p>@Wes : Well I have at least three sources that confirm that Knights get stronger in Rapid and Blitz.</p>

<p>The first is GM Vlastmil Hort which I previously quoted. He had a peak rating of 2620 Elo and even reached the 1977–78 Candidates Tournament.</p>

<p>The second is <a href="http://www.chess.com/news/krushs-last-minute-run-edges-kosintseva-in-death-match-4693" rel="noreferrer">this news report from Chess.com</a> about a "death match" which happened only a week ago.</p>

<blockquote>
  <p>"Before the match, I thought it was easier to play in blitz with the knight, not the bishop," GM Kosintseva said, reflecting the popular notion that knights can be very tricky with minimal time.</p>
</blockquote>

<p>The third source is <a href="http://www.chess.com/forum/view/general/knights-gt-bishops-in-blitz-games" rel="noreferrer">this Chess.com thread</a>, where a National Master said:</p>

<blockquote>
  <p>It does matter and knights are better in blitz !  Take it from someone who has played more than 50,000 blitz games ! Most titled players I talk about this with agree that knights are better in blitz than bishops.</p>
</blockquote>
 2180: <p>The Knight is not stronger in blitz, such a statement is nonsense.</p>

<p>It is you that are weaker at calculating at blitz, and the Knight is simply more difficult to handle with less time to calculate due to the kind of moves you can make with it.</p>

<p>So it's matter of how your brain handles Knights nothing intrinsic in the Knight.</p>
 3890: <p>I have no mathematical formula to calculate the value of a knight or bishop depending on the time control (which is a related question and was asked <a href="https://chess.stackexchange.com/questions/6249/worth-of-a-piece-in-time/6373#6373">here</a>), but as I am mainly a <a href="http://www.chess.com/" rel="noreferrer">Chess.com</a> user and thus play blitz and rapid on the internet, I'll try to make an educated guess. My answer will be based on chess played with a mouse, not OTB.</p>

<p>There are several factors while considering the numerical value of the knight and the bishop that have to be taken into account.</p>

<p>1.1. The bishop is a long range piece, and this means that you have to make longer moves when moving it and consider more squares it can attack and defend.</p>

<p>1.2. The knight is a short range piece, and thus you only have to care about a smaller part of the board when moving it.</p>

<p>2.1. The bishop can only control half the board, and thus your opponent may easily avoid it by simply placing his pieces on the opposite color.</p>

<p>2.2. The knight, albeit slower, can control the whole board, this means that your opponent's king is not safe of checks anywhere, and checks are quite time consuming (at least from a couple to a handful of seconds).</p>

<p>3.1. The bishop moves (diagonally) are very predictable.</p>

<p>3.2. The knight moves (L shape and able to jump over pieces) are hard to predict, and it's easy to blunder forks when one is hopping around you.</p>

<p>The references to time consuming moves may look quite odd to players that do not use the internet. However, they do play an important role, since the time control is so reduced that almost instant answers are needed in the endgame, and these cannot be easily reached by long-range pieces.</p>

<p>There may be more, but I consider these points, specially the last one, the most important. If we consider the pros and cons, clearly the surprise factor of the knight and the fact that he is more consuming to your opponent than the bishop, give him the upper hand. By experience, I have lost many games and draw winning positions being low on time and blundering a fork to a knight, and also spent a few extra seconds on the clock due to an unexpected check and ended up losing on time.</p>

<p>This is why I consider the knight to be at least <strong>4.00</strong> pawns, while the bishop keeps his <strong>3.25</strong> pawns. However, in some positions (all the pawns in one side, or all the pawns blocked, or the enemy king cut off, or similar positions where the knight can easily outmaneuver the bishop) I would give the knight a full pawn advantage at <strong>4.25</strong> pawns.</p>

<p>I am well aware that this answer is completely subjective, but as said, I couldn't find a way to quantify these advantages.</p>
