Pop Count is how many bloons a tower has popped. Every layer of a bloon a tower pops adds one to the towers pop count. In Bloons TD 5, every time a tower hits a Ceramic Bloon or MOAB-Class Bloon, that does not go to their pop count. However, if they get their multi-hit layer destroyed completely, it does count and gives the Pop count equivalent to the multi-hit layer bloon's children. In Bloons TD 6 and Bloons Adventure Time TD, damaging any multi-HP bloon (e.g. Ceramic Bloon and MOAB-Class Bloon) does count.
In BTD6, the Pop Count is now called the Damage Count, due to how significantly different the counter now counts, counting the amount of points of damage rather than the number of bloons popped. This allows specified damage-boosting upgrades to display a much more accurate reading of damage amount.
Gallery
Pop Count in BTD3
BTD4 Pop Count
BTD5 Pop Count
BTD6 pop count
A Rare Example of Negative Pop Count Achieved when the Bloon Master Alchemist Pops a Test Bloon.
Trivia
Even though some towers like the Banana Farm do not pop Bloons, they still have a pop count.
In the mobile version the Banana Farm doesn't have a pop count. Neither does the Monkey Village, which will get pop count if upgraded to High Energy Beacon though.
In BTD6, the Banana Farm doesn't have a pop count. However, the Monkey Village does have a pop count regardless of upgrades, even though it is only able to actually pop bloons with the Primary Expertise upgrade.
Before the 5.0 update in BTD6, the pop count increases with cash collected from Banana Farms or other money-making towers like Merchantmen.
This was replaced with a new "Cash Count" icon, but only appears for some cash generating towers. However, the "cash produced" icon now separately records cash generation and pop counts, starting from Version 19.0.
In Bloons TD 5 Mobile, the Pop Count counter becomes 0 when a tower gets upgraded. This also applies to Bloons Tower Defense Battles Mobile and Bloons Monkey City Mobile, but in both cases it becomes normal again when that tower pops a bloon or if the player exits the tower's menu and reopens it.
In BTD6, the pop count is now replaced with a damage count which will increase with each hit rather than each pop, including the RBE of MOAB-Class Bloons.
Prior to the Version 19.0 change to Damage Count separating from Income Count, Banana Farms also had a pop count that was equal to the amount of money they have produced. This was the same with Merchantmen, and along with all other monkeys that primarily produce money.
From the 5.0 update until before 19.0, Towers that produce money have a banana symbol for their cash count instead of the default one. However, towers and heroes that both produce cash and pop bloons such as the Merchantman and Benjamin would still have the default pop count added on to their cash count.
