Straight from Stadium2, all the info to find which POKéMON you want in POKéMON Red.
Bulbasaur
Gotten from Prof. Oak.
Level 5
One per game.
Ivysaur
Evolved from a Bulbasaur.
Venusaur
Evolved from an Ivysaur.
Charmander
Gotten from Prof. Oak.
Level 5
One per game.
Charmeleon
Evolved from a Charmander.
Charizard
Evolved from a Charmeleon.
Squirtle
Gotten from Prof. Oak.
Level 5
One per game.
Wartortle
Evolved from a Squirtle.
Blastoise
Evolved from a Wartortle.
Caterpie
Viridian Forest
Level 3
Rarely
Route 25
Level 8
Maybe
Metapod
Viridian Forest
Level 4
Rarely
Route 25
Level 7
Rarely
Butterfree
Evolved from a Metapod.
Weedle
Route 2
Level 3 to 5
Sometimes
Viridian Forest
Level 3 to 5
Often
Route 24
Level 7
Sometimes
Route 25
Level 8
Sometimes
Kakuna
Viridian Forest
Level 4 to 6
Usually
Route 24
Level 8
Sometimes
Route 25
Level 9
Sometimes
Beedrill
Evolved from a Kakuna.
Pidgey
Route 1
Level 2 to 5
Often
Route 2
Level 3 to 5
Often
Route 3
Level 6 to 8
Often
Route 5 and 6
Level 13 to 16
Usually
Route 7
Level 19 to 22
Usually
Route 8
Levels 18 to 20
Usually
Route 12
Level 23 to 27
Usually
Route 13
Level 25 to 27
Usually
Route 14
Level 26
Sometimes
Route 15
Level 23
Sometimes
Route 21
Level 21 to 23
Usually
Route 24
Level 12 to 13
Sometimes
Route 25
Level 13
Sometimes
Pidgeotto
Route 14 and 15
Level 28 to 30
Rarely
Route 21
Level 30 to 32
Sometimes
Pidgeot
Evolved from a Pidgeotto.
Rattata
Route 1 and 22
Level 2 to 4
Often
Route 2
Level 2 to 5
Usually
Route 4
Level 8 to 12
Usually
Route 9
Level 14 to 17
Usually
Route 16
Level 18 to 22
Usually
Route 21
Level 21 to 23
Usually
Raticate
Route 16
Level 23 to 25
Rarely
Route 17
Level 25 to 29
Usually
Route 18
Level 25 to 29
Sometimes
Route 21
Level 30
Sometimes
Spearow
Route 3
Level 5 to 8
Often
Route 4
Level 8 to 12
Usually
Route 9, 10, and 11
Level 13 to 17
Usually
Route 16, 17, and 18
Level 20 to 22
Usually
Route 22
Level 3 to 5
Not Often
Route 23
Level 26
Sometimes
Fearow
Route 17
Level 25 to 27
Rarely
Route 18
Level 25 to 29
Sometimes
Route 23
Level 38 to 43
Usually
Ekans
Route 4
Level 6 to 12
Usually
Route 8
Level 17 to 19
Sometimes
Route 9 and 10
Level 11 to 17
Usually
Route 11
Level 12 to 15
Usually
Route 23
Level 26
Sometimes
Arbok
Route 23
Level 41
Rarely
Cerulean Cave
1F
Level 52
Not often
B1F
Level 57
Rarely
Pikachu
Viridian Forest
Level 3 to 5
Rarely
Power Plant
Level 20 to 24
Usually
Raichu
Cerulean Cave
1F
Level 53
Rarely
B1F
Level 64
Not Often
Sandshrew
None available in-game.
Sandslash
None available in-game.
Nidoran(f)
Route 22
Level 3 to 4
Rarely
Safari Zone
Area 1
Level 24
Rarely
Area 3
Level 25
Rarely
Nidorina
Celadon City Game Corner (1200 coins needed)
Level 17
Safari Zone
Center Area
Level 31
Rarely
Area 2
Level 30
Rarely
Nidoqueen
Evolved from a Nidorina with a Moon Stone.
Nidoran(m)
Route 22
Level 2 to 4
Usually
Safari Zone
Center Area
Level 22
Sometimes
Area 1
Level 24
Sometimes
Area 2
Level 22
Sometimes
Area 3
Level 25
Sometimes
Nidorino
Safari Zone
Center Area
Level 31
Not Often
Area 1
Level 33
Not Often
Area 2
Level 30
Not Often
Area 3
Level 33
Not Often
Nidoking
Evolved from a Nidorino with a Moon Stone.
Clefairy
Mt. Moon
1F
Level 8
Maybe
B1F
Level 9
Rarely
B2F
Level 10 to 12
Not Often
Celadon City Game Corner (500 coins needed)
Level 8
Clefable
Evolved from a Clefairy with a Moon Stone.
Vulpix
None available in-game.
Ninetails
Evolved from a Vulpix with a Fire Stone.
Jigglypuff
Route 3
Level 3 to 7
Not Often
Wigglytuff
Cerulean Cave
2F
Level 54
Rarely
Zubat
Mt. Moon
1F
Level 6 to 11
Often
B1F
Level 7 to 11
Often
B2F
Level 9 to 12
Often
Rock Tunnel
B1F
Level 15 to 18
Often
B2F
Level 16 to 18
Often
Seafoam Islands
1F
Level 21
Not Often
Victory Road
1F and 3F
Level 22
Sometimes
2F
Level 26
Sometimes
Golbat
Seafoam Islands
1F
Level 29
Rarely
B2F
Level 30
Rarely
B4F
Level 32
Maybe
Victory Road
1F and 3F
Level 41
Rarely
2F
Level 40
Rarely
Cerulean Cave
1F
Level 46
Sometimes
Oddish
Route 5 and 6
Level 13 to 16
Usually
Route 7
Level 19 to 22
Usually
Route 12, 13, 14, and 15
Level 22 to 26
Usually
Route 24 and 25
Level 12 to 14
Usually
Gloom
Route 12 and 13
Level 28 to 30
Rarely
Route 14 and 15
Level 30
Rarely
Vileplume
Evolved from a Gloom with a Leaf Stone.
Paras
Mt. Moon
1F
Level 8
Rarely
B1F
Level 10
Not Often
B2F
Level 10 to 12
Sometimes
Safari Zone
Area 1
Level 22
Sometimes
Area 2
Level 23
Sometimes
Parasect
Safari Zone
Center Area
Level 30
Rarely
Area 1
Level 25
Rarely
Cerulean Cave
1F
Level 52
Rarely
B1F
Level 64
Not Often
Venonat
Route 12, 13, and 14
Level 24 to 26
Sometimes
Route 15
Level 26 to 28
Sometimes
Safari Zone
Center Area
Level 22
Sometimes
Area 3
Level 23
Sometimes
Venomoth
Safari Zone
Area 2
Level 32
Rarely
Area 3
Level 31
Rarely
Victory Road
Level 40
Not Often
Cerulean Cave
2F
Level 51
Sometimes
1F
Level 49
Not Often
Diglett
Diglett's Cave
Level 15 to 22
Abundant
Dugtrio
Diglett's Cave
Level 29 to 31
Rarely
Meowth
None available in-game.
Persian
Evolved from a Meowth.
Psyduck
Route 24 and 25
Super Rod
Level 15
Usually
Safari Zone
Center Area, Area 1, 2, and 3
Super Rod
Level 15
Usually
Seafoam Islands
1F
Level 28
Rarely
Cerulean City
Super Rod
Level 15
Usually
Golduck
Seafoam Islands
1F
Level 38
Maybe
Mankey
Route 5 and 6
Level 10 to 16
Usually
Route 7
Level 17 to 20
Usually
Route 8
Level 18 to 20
Usually
Primeape
Evolved from Mankey.
Growlithe
Route 7
Level 18 to 20
Not Often
Route 8
Level 15 to 18
Sometimes
POKéMON Mansion
1F
Level 34
Not Often
2F
Level 32
Sometimes
3F
Level 33
Sometimes
B1F
Level 35
Sometimes
Arcanine
Evolved from a Growlithe with a Fire Stone.
Poliwag
Pallet Town, Viridian City, and Route 22
Good Rod
Level 10
Often
Super Rod
Level 15
Often
Cerulean City, Vermilion City, S.S. Anne, Celadon City, Fuchsia City, Safari Zone, Seafoam Islands B3F, B4F, Cinnabar Town, Cerulean Cave, Route 6, 10, 11, 12, 13, 17, 18, 19, 20, 21, 23, 24, and 25
Good Rod
Level 10
Often
Poliwhirl
Route 10 and Celadon City
Super Rod
Level 23
Often
Poliwrath
Evolved Poliwhirl with a Water Stone.
Abra
Route 24
Level 8 to 12
Sometimes
Route 25
Level 10 to 12
Sometimes
Celadon City Game Corner (180 coins needed)
Kadabra
Cerulean Cave
2F
Level 51
Sometimes
1F
Level 49
Rarely
Alakazam
Gotten through trading a Kadabra to/from any version.
Machop
Rock Tunnel
B1F and B2F
Level 15 to 17
Sometimes
Victory Road
1F and 3F
Level 24
Sometimes
2F
Level 22
Sometimes
Machoke
Victory Road
1F
Level 42
Rarely
2F
Level 41
Rarely
3F
Level 42 to 45
Rarely
Machamp
Gotten through trading a Machoke to/from any version.
Bellsprout
Not available in-game.
Weepinbell
Evolved from Bellsprout.
Victreebel
Evolved from a Weepinbell with a Leaf Stone
Tentacool
Pallet Town, Viridian City, Route 12, 13, 17, and 18
Super Rod
Level 15
Often
Route 19, 20, and 21
Surfing
Level 5 to 40
Always
Tentacruel
Evolved from a Tentacool.
Geodude
Mt. Moon
1F
Level 8 to 10
Sometimes
B1F
Level 7 to 9
Usually
B2F
Level 9 to 10
Usually
Rock Tunnel
B1F
Level 16 to 17
Usually
B2F
Level 16 to 18
Usually
Victory Road
1F and 3F
Level 26
Sometimes
2F
Level 24
Sometimes
Graveler
Victory Road
1F
Level 41
Rarely
2F
Level 43
Maybe
3F
Level 43
Rarely
Golem
Gotten through trading a Graveler to/from any version.
Ponyta
POKéMON Mansion
1F
Level 28 to 34
Usually
2F
Level 28 to 32
Usually
3F
Level 32 to 36
Usually
B1F
Level 32 to 34
Sometimes
Rapidash
Evolved from a Ponyta.
Slowpoke
Route 10, Celadon City, and Safari Zone
Super Rod
Level 15
Usually
Seafoam Islands
1F
Level 30
Sometimes
B1F
Level 28 to 30
Sometimes
B2F
Level 30 to 32
Usually
B3F
Level 31 to 33
Usually
B4F
Level 29 to 31
Sometimes
Slowbro
Seafoam Islands
B2F
Level 37
Maybe
B4F
Level 39
Rarely
Route 23, Cerulean Cave
Super Rod
Level 23
Usually
Magnemite
Power Plant
Level 21 to 23
Usually
Magneton
Power Plant
Level 32 to 35
Not Often
Cerulean Cave
1F
Level 46
Sometimes
Farfetch'd
Gotten through an in-game trade.
Doduo
Route 16
Level 18 to 22
Usually
Route 16 and 17
Level 24 to 28
Usually
Safari Zone
Area 1 and 3
Level 26
Sometimes
Dodrio
Cerulean Cave
2F
Level 51
Sometimes
1F
Level 49
Not Often
Seel
Seafoam Islands
1F
Level 30
Sometimes
B1F
Level 28 to 30
Sometimes
B2F
Level 30 to 32
Usually
B3F
Level 31 to 33
Usually
B4F
Level 29 to 31
Sometimes
Dewgong
Seafoam Islands
B1F
Level 38
Rarely
B3F
Level 37
Maybe
Grimer
POKéMON Mansion
1F and 2F
Level 30
Rarely
3F
Level 34
Rarely
B1F
Level 35
Rarely
Muk
POKéMON Mansion
1F
Level 39
Maybe
2F
Level 37
Maybe
3F and B1F
Level 42
Maybe
Shellder
Vermilion City, S.S. Anne, Cinnibar Town, Route 6, and 11
Super Rod
Level 15
Often
Route 19, 20, and 21
Super Rod
Level 15
Usually
Seafoam Islands
1F
Level 28 to 30
Sometimes
B1F
Level 32
Sometimes
B2F
Level 28
Rarely
B3F
Level 29 to 31
Sometimes
Super Rod
Level 15
Usually
B4F
Level 31 to 33
Usually
Super Rod
Level 15
Usually
Cloyster
Evolved from a Shellder with a Water Stone.
Ghastly
POKéMON Tower
3F, 4F, and 5F
Level 18 to 24
Abundant
6F
Level 19 to 24
Abundant
7F
Level 20 to 24
Often
Haunter
POKéMON Tower
3F
Level 25
Maybe
4F and 5F
Level 25
Rarely
6F
Level 26 to 28
Not Often
7F
Level 28 to 30
Sometimes
Gengar
Gotten through trading a Haunter to/from any version.
Onix
Rock Tunnel
B1F
Level 13 to 15
Rarely
B2F
Level 13 to 17
Not Often
Victory Road
1F and 2F
Level 36 to 42
Usually
3F
Level 42 to 45
Sometimes
Drowzee
Route 11
Level 9 to 15
Usually
Hypno
Cerulean Cave
1F
Level 46
Sometimes
Krabby
Cerulean City, Fuchsia City, Safari Zone, Route 12, 13, 17, 18, 24, and 25
Super Rod
Level 15
Usually
Vermilion City, S.S. Anne, Route 6, and 11
Super Rod
Level 15
Often
Kingler
Route 23, Cerulean Cave 1F and B1F
Super Rod
Level 23
Usually
Voltorb
Route 10
Level 14 to 17
Usually
Power Plant
Level 21 to 23
Usually
Electrode
Cerulean Cave
2F
Level 52
Not Often
B1F
Level 55
Sometimes
Exeggcute
Safari Zone
Center Area
Level 24 to 25
Sometimes
Area 1
Level 23 to 25
Sometimes
Area 2
Level 25 to 27
Sometimes
Area 3
Level 24 to 26
Sometimes
Exeggutor
Evolvled from an Exeggcute with a Leaf Stone
Cubone
POKéMON Tower
3F, 4F, and 5F
Level 20 to 22
Not Often
6F and 7F
Level 22 to 24
Not Often
Marowak
Victory Road
1F
Level 43
Maybe
2F
Level 40
Rarely
Cerulean Cave
2F
Level 52
Not Often
B1F
Level 55
Sometimes
Hitmonlee
Gotten from the fighting gym master.
Level 20
One per game.
Hitmonchan
Gotten from the fighting gym master.
Level 20
One per game.
Lickitung
Gotten through an in-game trade.
Koffing
POKéMON Mansion
1F
Level 30 to 32
Usually
2F
Level 30 to 34
Often
3F
Level 31 to 35
Usually
B1F
Level 31 to 33
Often
Weezing
POKéMON Mansion
1F
Level 37
Rarely
2F
Level 39
Rarely
3F
Level 38 to 40
Sometimes
B1F
Level 40 to 42
Sometimes
Rhyhorn
Safari Zone
Center Area
Level 25
Sometimes
Area 2
Level 26
Sometimes
Rhydon
Cerulean Cave
2F
Level 52
Not Often
B1F
Level 55
Sometimes
Chansey
Safari Zone
Center Area
Level 23
Maybe
Area 2
Level 26
Rarely
Cerulean Cave
2F
Level 56
Rarely
B1F
Level 64
Not Often
Tangela
Route 21
Level 28 to 32
Not Often
Kangaskhan
Safari Zone
Area 1
Level 25
Rarely
Area 3
Level 28
Maybe
Horsea
Cinnibar Town, Route 19, 20, and 21
Super Rod
Level 15
Usually
Seafoam Islands
1F
Level 28 to 30
Sometimes
B1F
Level 30 to 32
Usually
B2F
Level 28 to 30
Sometimes
B3F
Level 29 to 31
Sometimes
Super Rod
Level 15
Usually
B4F
Level 31 to 33
Usually
Super Rod
Level 15
Usually
Seadra
Seafoam Islands
B1F
Level 37
Maybe
B3F
Level 39
Rarely
Route 23
Super Rod
Level 23
Usually
Cerulean Cave
1F and B1F
Level 23
Usually
Goldeen
Pallet Town, Viridian City, Vermilion City, S.S. Anne, Celadon City, Safari Zone, Cerulean Cave, Route 6, 10, 11, and 23
Good Rod
Level 10
Often
Cerulean City, Seafoam Islands B3F, B4F, Cinnibar Town, Route 12, 13, 17, 18, 19, 20, 21, 24, and 25
Good Rod
Level 10
Often
Super Rod
Level 15
Usually
Route 22
Good Rod
Level 10
Often
Super Rod
Level 15
Often
Seaking
Fuchsia City, Cerulean Cave, and Route 23
Super Rod
Level 23
Usually
Staryu
Cinnibar Town, Route 19, 20, and 21
Super Rod
Level 15
Usually
Seafoam Islands
B1F
Level 30
Sometimes
B2F
Level 30
Not Often
B3F and B4F
Super Rod
Level 15
Usually
Starmie
Evolved from a Staryu with a Water Stone.
Mr. Mime
Gotten through an in-game trade.
Scyther
Celadon City Game Corner (5500 coins needed)
Level 25
Safari Zone
Center Area
Level 23
Rarely
Area 1
Level 28
Maybe
Jynx
Gotten through an in-game trade.
Electabuzz
Power Plant
Level 33 to 36
Rarely
Magmar
Not available in-game.
Pinsir
Not available in-game.
Tauros
Safari Zone
Area 2
Level 28
Maybe
Area 3
Level 26
Rarely
Magikarp
Pallet Town, Viridian City, Cerulean City, Vermilion City, S.S. Anne, Celadon City, Safari Zone, Seafoam Islands, Cinnibar Town, Cerulean Cave, Route 6, 10, 11, 19, 20, 21, 22, 23, 24, and 25
Old Rod
Level 5
Always
Fuchsia City, 12, 13, 17, and 18
Old Rod
Level 5
Always
Super Rod
Level 15
Usually
Gyarados
Evolved from a Magikarp.
Lapras
Gotten from a man in the Silph Co. building.
Level 15
One per game.
Ditto
Route 13
Level 25
Rarely
Route 14
Level 23
Sometimes
Route 15
Level 26
Sometimes
Route 23
Level 33 to 43
Usually
Cerulean Cave
2F
Level 55 to 60
Rarely
1F
Level 53
Maybe
B1F
Level 63 to 67
Not Often
Eevee
Gotten from a man in the Celadon Manison.
One per game.
Vaporeon
Evolved from an Eevee with a Water Stone.
Jolteon
Evolved from an Eevee with a Thunder Stone.
Flareon
Evolved from an Eevee with a Fire Stone.
Porygon
Celadon City Game Corner (9999 coins needed)
Level 26
Omanyte
Cinnibar Island Lab (Helix Fossil needed)
Level 30
One per game.
Omastar
Evolved from a Omanyte.
Kabuto
Cinnibar Island Lab (Dome Fossil needed)
Level 30
One per game.
Kabutops
Evolved from a Kabuto.
Aerodactyl
Cinnibar Island Lab (Old Amber needed)
Level 30
One per game.
Snorlax
Route 11
Level 30
Two per game.
Articuno
Seafoam Islands
B4F
Level 50
One per game.
Zapdos
Power Plant
Level 50
One per game.
Moltres
Victory Road
2F
Level 50
One per game.
Dratini
Celadon City Game Corner (2800 coins needed)
Level 18
Safari Zone
Area 1, 2, 3, and Center Area
Super Rod
Level 15
Usually