How do you tell what IVs your Pokemon have in bw?

Question

and xy

Answer 1

IV Checker
Location: Gear Station - Nimbasa City
In the Gear Station, you will find a guy who will judge you based upon your Pokémon's Individual Values. He will tell you which stat is the best stat of your Pokémon and will then tell you how good it is, saying if it's Decent, Very Good, Fantastic or Can't be Better.

IV Judge
Location: Kiloude City
In the Pokémon Center is the special IV Judge. This man will tell you the best of your Pokémon's stats, in fact telling you multiple stats this time. In addition to that, he will rate the overall potential your Pokémon has, giving a rating of all of the IVs of the Pokémon.

For Pokemon BW, your Pokemon's IVs will be told by the IV Checker.
For Pokemon XY, your Pokemon's IVs will be told by the IV Judge.
For IVs that aren't 31, and if you want to find out the exact IVs, that will require an IV Calculator.

Source (BW)
Source (XY)

Comments

This is correct

Answer 2

There are 2 useful ways to tell the amount of IVs your Pokemon has..

If you're looking to see exactly what IVs your Pokemon has, then you could use a stat calculator such as this one from marriland. (This calculator will work for generations III-VI) However, you will need to know what EVs your Pokemon has in each stat, which is kind of a bummer.

If you're willing to use EV reducing berries to reset your Pokemon's EVs, there is a Pokemon Breeder♀ next to the west entrance of Nimbasa City who will sell 5 of the same type of EV reducing berries to you every day in Pokemon White 2 and Black 2. The type of EV reducing berry she gives you depends on your leading Pokemon's highest base stat. You can also receive every type of EV reducing berry from a rank 10 Join Avenue florist.

In Pokemon X and Y, you can use a Reset Bag in the Pokemon Training Regimen Screen to reset your Pokemon's EVs. You can obtain this bag by having your Pokemon punch the default, clear punching bag while you still have an empty slot in your punching bag inventory.

If you're just checking to see whether or not your Pokemon has perfect IVs or if you're alright with just a rough explanation of your Pokemon's IVs, then you can consult the IV judge, who can be located in the Gear Station in Nimbase City in all Generation V games or in the Pokemon Center in Kiloude City in Pokemon X & Y.
The amount of IVs your Pokemon has in a certain stat will depend on what the judge says:

• rather decent: 0-15 IVs
• good: 16-25 IVs
• fantastic: 26-30 IVs
• can't be better/can't be beat: 31 IVs

Sources:
Bulbapedia Article on the Stats Judge
Join Avenue Florist Merchandise Chart from Pkmn.net

Answer 3

In Gear Station in Nimbassa City a man closest to the entrance will check your IVs on BW
There is a man in Kiloude City inside the Pokémon Centre for XY
You can also check them via the link