WHIRLWIND EXPLANATION: Pokémon have a fixed, permanent score from 0 to 31 for each stat that affects how good that stat can ever get.

This calculator will figure out that score (called a "gene" or, more obtusely, an "IV") for you, so you can discard the unworthy. It's more accurate for higher-level Pokémon, so it's helpful to go into a level 100 wifi battle with someone and check your Pokémon's stats from there.

Stat calculator

Gyarados
Gyarados 		Base
stats		 Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Stats Effort Possible genes (IVs)
Level Level Level Level Level Level Level Level Level Level Level
HP 95
68–74
70–77
73–80
76–83
79–87
82–90
88–96
91–99
94–103
97–106
108–119
21
Attack 125
55–61
57–64
60–66
62–69
65–72
67–75
72–80
75–83
77–86
80–89
90–100
30
Defense 79
36–42
38–44
39–46
41–48
42–50
44–52
47–56
49–57
50–59
52–61
58–69
8
Special Attack 60
29–35
30–36
31–38
32–39
33–41
35–42
37–45
38–47
39–48
41–50
45–56
5
Special Defense 100
45–51
47–53
49–55
51–58
53–60
55–62
59–67
61–69
63–71
65–74
73–83
5
Speed 81
37–43
39–45
40–47
42–49
43–51
45–53
48–57
50–59
51–60
53–62
60–70
10

Congratulations, you've narrowed your Pokémon's stats down exactly!

This Gyarados's Hidden Power inflicts Electric damage, with 36 power.

And for your copy/pasting pleasure:

21 HP; 30/8 Physical; 5/5 Special; 10 Speed

or start over