Why at Pokerstars clicking a pot button adds 1000 more?

Question

I played a 250/500 no-limit Hold'em cash game at Pokerstars and noticed the following:

If no one has raised yet, the preflop pot size is P = 750 (BB + SB). There is a pot button, clicking pot + raise buttons adds (1000 + P) into the pot. If there were 750 chips in the pot, I would add 1750 more. The pot would now be of size 2500 and others would need to add up to 1750 to call.

However, if I click the 3bb + raise buttons, I am only adding 1500 into the pot.

Question: What is this extra 1000 for?

Answer 1

The size of a pot-sized raise is calculated as follows:

1. Match the standing bet, and then
2. Raise by the size of the pot after you have matched the current bet.

The formula for calculating this is 3x current bet + dead money. Why does this formula work? Let's use actual numbers so we can see more clearly:

Example 1: SB posts 250, BB posts 500. You are UTG and you want to put in a pot-sized raise. We first match the current bet (500), then we calculate the amount in the pot (500+500+250=1250). The total amount you would put in is therefore 500+1250=1750.

In the above example, the three 500 and the 250 sums to a total of a pot-sized raise: 1750.

Example 2: The pot is 1000. On the flop, SB bets 400. You in the BB wants to put in a pot-sized raise. We first match the current bet (400), then we calculate the amount in the pot (400+400+1000=1800). The total amount you would put in is therefore 400+1800=2200.

In the above example, we use the formula 3x400+1000=2200.