The Binding of Isaac Wiki

Shot Speed[]

Shot speed is a stat that increases the rate at which tears travel. An increased shot speed will also increase knockback from tears.  Shot speed up will also decrease the effectiveness of A Lump of Coal, because with Lump of Coal, damage increases with the duration tears are on screen. And because shot speed up decreases the amount of time tears are on screen, it reduces damage.



Luck, although not shown on the menu, affects the probability to find an item after clearing a room and also changes the probability of Tough Love making a tooth shot. Its base value is 0.

Ironically, neither the Lucky Foot nor the Lucky Toe have an effect on Luck -  the only way to change the Luck stat is by using the pills with which it is associated - Luck Up and Luck Down.

Tough Love[]

Tough Love will shoot teeth with a probability of 1/(10 - Luck).

Effect on Room Clearing[]

  • When a room is cleared, a random decimal number between 0 and 1, chance, is generated.
  • Having the Lucky Foot will cause chance to be set to chance * 0.9 + 0.1.
  • Following this, the game repeats the same operation on chance if Luck is positive - chance is set to chance * 0.9 + 0.1.
  • However, if Luck is negative, Luck * 0.1 is subtracted from chance. Notably, this means that negative Luck will actually increase chance.
  • Having the Lucky Toe, positive luck, and the Lucky Foot will cause chance to be set to chance * 0.98 + 0.02.
  • Having the Lucky Toe but not one of the other 2 attributes will cause chance to be set to chance * 0.9 + 0.1.


  • Chance under 0.22 will result in no item being dropped
  • Chance between .22 and .3 results in the following chain:
    • 1/3 chance of a card being dropped
    • Else, 1/2 chance of a trinket being dropped
    • Else, a pill is dropped
  • Chance between 0.3 and 0.45 results in a coin being dropped
  • Chance between 0.45 and 0.6 results in a heart being dropped
  • Chance between 0.6 and 0.8 - Currrent Chapter * 0.01 results in a key being dropped
  • Chance between 0.8 - Currrent Chapter * 0.01 and .95 results in a bomb being dropped
  • Chance above .95 results in a treasure chest being dropped.


  • The challenge "7 Years Bad Luck" sets starting Luck to -2.
  • Luck is a visible stat in rebirth, just like shot speed.

Negative Luck[]

Negative Luck (such as in "7 Years Bad Luck" challenge), ironically, actually increases the rate at which items drop upon clearing a floor. For example, having -2 Luck will result in no item dropping 2.5% of the time - a staggeringly low percentage. However, having negative luck in tandem with the Lucky Foot, the Lucky Toe, or both will severly drop the chance of obtaining a card, trinket, or pill, sometimes even removing the possibility if Luck is sufficiently negative.


The Special stat, which has a starting value of 0, is used for determining the chance that a special item will be created in an item creation process like the opening of a Golden Chest or the entering of an Angel Room. The lower the Special stat is, the higher the chance that a special item will appear.

Special and Item Generation[]

  • When an item is generated, if it is not special, it is spawned.
  • When an item is generated, if it is special, the chance that it is generated again is 1 - 1 / (1.2 + Special * 3).
    • This means at the start, there is an 83.3% chance of keeping a generated special item, but after picking up just one, this chance falls to 23.8%
  • If an item is special and not obtained by a Deal With the Devil, Special is incremented by 1. My Reflection only adds 0.2 to Special.
  • Samson spawns with Bloody Lust, meaning his special counter starts at 1 and therefore has a 23.8% chance to keep any special items which are generated instead of the 83.3% which all other characters start with.

Special Items[]