how does Stealth Rock damage calculation work?

[onionchowder]

OK, so i was thinking of running reversal on my CS scyther (to "abuse" SR), and i was wondering how the damage calculations work

for example, if scyther has 280 HP, and it comes in on SR, it loses 140 HP.

but if scyther has 281 HP, will it lose 140 or 141?

what about 282? 283?

i just need to know if SR-reversal is possible

 

[Toothache]

The basic rule of thumb in this case is to remember in Pokemon everything rounds down, even things over 0.5 difference (18.75% rounds down to 18% for example), at each individual stage.

In this case anything between 280-283 HP will only take 140 damage from Stealth Rock, so it can come in up to 2 of them provided it takes no other damage.

Reversal reaches max power at less than 4% of max HP (3.125% to be specific), or in this case a Scyther with less than 10 HP.

 

[onionchowder]

so if i'm thinking of using reversal, i ought to have 281 HP?

funny... i THINK my scyther ATM has 281 HP, and i think it was killed by 2 SR, maybe i'm wrong...

 

[Seph]

Simple questions like these should be asked in the Ask a simple question, get a simple answer thread.

http://www.smogon.com/forums/showthread.php?t=36399

 

[Mekkah]

odd HP = you die in two stealth rock hits
even HP = you die in three (after two you have 1hp left)

So Toothache is in fact wrong. If it had 282 or 283 HP, it will take 141 damage from SR