How Many Pokémon Can You Get with Only Pokémon Silver?
Assuming you do not use any glitches, the answer is 199. The Professor Oak challenge guide for Silver can be found here, although I've made a shorter list of encounters below in case anything happens to the external guide.
It is possible to obtain evolutionary stones via Mystery Gift, making it technically possible to get all Pokémon that evolve with Leaf, Water, Fire, and Thunderstones. However, receiving an evolutionary stone this way is extremely unlikely.
The list of Pokémon you cannot get without trading, which equals 52 species, is as follows:
- Two Starters (6) - 6 total
- As you can only select one starter Pokémon, the other two starters, and their evolutions, are unavailable; this totals 6 Pokémon.
- Trade Evolutions (10) - 16 total
- Alakazam, Machamp, Golem, Gengar, Politoed, Slowking, Steelix, Scizor, Kingdra, and Porygon2 evolve by trade. Without the ability to trade, they are unobtainable.
- Version Exclusives (10) - 26 total
- The following Pokémon cannot be obtained without the use of glitches or trading: Spinarak, Ariados, Growlithe, Arcanine, Mankey, Primeape, Gligar, Teddiursa, Ursaring, and Mantine.
- Leaf Stone Pokémon (2) - 28 total
- As only one Leaf Stone is obtainable, only one of Victreebel, Vileplume, or Exeggutor is obtainable.
- Water Stone Pokémon (3) - 31 total
- As only one Water Stone is obtainable, only one of Poliwrath, Starmie, Cloyster, or Vaporeon is obtainable.
- Fire Stone Pokémon (1) - 32 total
- As only one Fire Stone is obtainable, only one of Ninetales or Flareon is obtainable.
- Thunderstone Pokémon (1) - 33 total
- As only one Thunderstone is obtainable, only one of Raichu or Jolteon is obtainable.
- Red, Green, Blue, or Yellow Pokémon (17) - 50 total
- Bulbasaur, Ivysaur, Venusaur, Charmander, Charmeleon, Charizard, Squirtle, Wartortle, Blastoise, Omanyte, Omastar, Kabuto, Kabutops, Articuno, Zapdos, Moltres, and Mewtwo can only be obtained from Red, Green, Blue, or Yellow.
- Mythical/Event (2) - 52 total
- Outside of glitches, Mew and Celebi were only obtainable via events that are no longer active.
Professor Oak Challenge Notes
Pre-Badge 1 (Falkner) - 33 Total Pokémon
It is possible to get a Moon Stone to evolve Jigglypuff before defeating Falkner by storing all money with the player's mom, selling all items, and acquiring enough daily Berries to sell to give her more money.
- Gift in New Bark Town: One starter & its evolutions (3 total)
- Walking on Route 29: Pidgey, Pidgeotto, Pidgeot (6 total)
- Walking on Route 29: Sentret, Furret (8 total)
- Walking on Route 29: Hoothoot, Noctowl (10 total)
- Walking on Route 29: Rattata, Raticate (12 total)
- Walking on Route 46: Geodude, Graveler (14 total)
- Walking on Route 46: Jigglypuff, Wigglytuff (16 total)
- Walking on Route 46: Spearow, Fearow (18 total)
- Walking on Route 30: Weedle, Kakuna, Beedrill (21 total)
- Walking on Route 30: Ledyba, Ledian (23 total)
- Walking on Route 31: Bellsprout, Weepinbell (25 total)
- Walking in Dark Cave (Route 31/46 side): Zubat, Golbat, Crobat (28 total)
- Walking in Dark Cave (Route 31/46 side): Dunsparce (29 total)
- In-game Trade in Violet City: Onix: Trade your Bellsprout (30 total)
- Walking in Sprout Tower: Gastly, Haunter (32 total)
- Walking in Ruins of Alph Inside: Unown (33 total)
Badge 1 through Badge 2 (Bugsy) - 67 Total Pokémon
To use Headbutt here before being able to use Cut, you will need to use Slowpoke, who learns Headbutt at level 34.
- Gift (Egg) in Violet City: Togepi, Togetic (35 total)
- Walking on Route 32: Mareep, Flaaffy, Ampharos (38 total)
- Walking on Route 32: Hoppip, Skiploom, Jumpluff (41 total)
- Walking on Route 32: Wooper, Quagsire (43 total)
- Walking on Route 32: Ekans, Arbok (45 total)
- Fishing (Old Rod) in New Bark Town: Magikarp, Gyarados (47 total)
- Fishing (Old Rod) in New Bark Town: Tentacool, Tentacruel (49 total)
- Fishing (Old Rod) in Cherrygrove City: Krabby, Kingler (51 total)
- Fishing (Old Rod) on Route 30: Poliwag, Poliwhirl (53 total)
- Fishing (Old Rod) in Dark Cave (Route 31/46 side): Goldeen, Seaking (55 total)
- Fishing (Old Rod) on Route 32: Qwilfish (56 total)
- Walking in Slowpoke Well 1F: Slowpoke, Slowbro (58 total)
- Walking in Ilex Forest: Oddish, Gloom (60 total)
- Walking in Ilex Forest: Paras, Parasect (62 total)
- Headbutt (Common, Rare) on Route 29: Aipom (63 total)
- Headbutt (Rare) on Route 29: Heracross (64 total)
- Headbutt (Common, Rare) in Ilex Forest: Exeggcute (65 total)
- Headbutt (Rare) in Ilex Forest: Pineco, Forretress (67 total)
Badge 2 through Badge 3 (Whitney) - 97 Total Pokémon
- Walking on Route 34: Drowzee, Hypno (69 total)
- Walking on Route 34: Abra, Kadabra (71 total)
- Walking on Route 34: Ditto (72 total)
- Route 34: Breed Jigglypuff or Wigglytuff to get Igglybuff (73 total)
- Purchase in Goldenrod Game Corner: Sandshrew, Sandslash (75 total)
- Purchase in Goldenrod Game Corner: Dratini, Dragonair, Dragonite (78 total)
- In-game Trade in Goldenrod Department Store 5F: Machop, Machoke: Trade your Drowzee (80 total)
- Walking on Route 35: Nidoran♀, Nidorina (82 total)
- Walking on Route 35: Nidoran♂, Nidorino (84 total)
- Walking on Route 35: Yanma (85 total)
- Walking in National Park: Sunkern (86 total)
- Walking in the Bug-Catching Contest: Scyther (87 total)
- Walking in the Bug-Catching Contest: Pinsir (88 total)
- Walking in the Bug-Catching Contest: Caterpie, Metapod, Butterfree (91 total)
- Walking in the Bug-Catching Contest: Venonat, Venomoth (93 total)
- Evolve Gloom and Sunkern with Sun Stones from the Bug-Catching Contest: Vileplume, Sunflora (95 total)
- Walking on Route 36: Vulpix (96 total)
- Walking on Route 36: Stantler (97 total)
Badge 3 through Badge 4 (Morty) - 128 Total Pokémon
- Static encounter on Route 36: Sudowoodo (98 total)
- Gift in Goldenrod City: Eevee, Espeon (100 total)
- Route 34: Breed Espeon to get Eevee, and evolve it into Umbreon (101 total)
- Walking in the Burned Tower 1F: Koffing, Weezing (103 total)
- Walking in the Burned Tower B1F: Magmar (104 total)
- Route 34: Breed Magmar to get Magby (105 total)
- Walking on Route 38: Magnemite, Magneton (107 total)
- Walking on Route 38: Farfetch'd (108 total)
- Walking on Route 38: Miltank (109 total)
- Walking on Route 38: Tauros (110 total)
- Walking on Route 38: Snubbull, Granbull (112 total)
- Walking on Route 38: Meowth, Persian (114 total)
- In-game Trade in Olivine City: Voltorb, Electrode: Trade your Krabby (116 total)
- Rock Smash on Route 40: Shuckle (117 total)
- Fishing (Good Rod) in Olivine City: Corsola (118 total)
- Fishing (Good Rod) in Olivine City: Staryu (119 total)
- Fishing (Good Rod) in Olivine Harbor: Shellder (120 total)
- Fishing (Good Rod) in Olivine Harbor: Chinchou, Lanturn (122 total)
- Walking in Mt. Mortar 1F: Marill, Azumarill (124 total)
- Walking on Route 43: Girafarig (125 total)
- Roaming Legends: Raikou, Entei, Suicune (128 total)
Badge 4 through Badge 5 (Pryce) - 136 Total Pokémon
- Evolve a Moon Stone Pokémon with a Moon Stone from Tohjo Falls (129 total)
- Walking in Dark Cave (Route 46 side): Wobbuffet (130 total)
- Walking in the Ruins of Alph Outside: Natu, Xatu (132 total)
- Walking in the Ruins of Alph Outside: Smeargle (133 total)
- Static encounter in Union Cave B2F: Lapras (134 total)
- Surfing in Ilex Forest: Psyduck, Golduck (136 total)
Badges 5 through Badge 7 (Chuck) - 140 Total Pokémon
Badge 7 through Badge 8 (Clair) - 155 Total Pokémon
- Static encounter in Whirl Islands B3F: Lugia (141 total)
- Walking on Route 44: Lickitung (142 total)
- Walking on Route 44: Tangela (143 total)
- Fishing on Route 44: Remoraid, Octillery (145 total)
- Walking in the Ice Path: Jynx (146 total)
- Walking in the Ice Path: Delibird (147 total)
- Walking in the Ice Path: Swinub, Piloswine (149 total)
- In-game Trade in Blackthorn City: Rhydon: Trade your female Dragonair (150 total)
- Route 34: Breed Jynx to get Smoochum (151 total)
- Route 34: Breed Rhydon to get Rhyhorn (152 total)
- Walking on Route 45: Phanpy, Donphan (154 total)
- Walking on Route 45: Skarmory (155 total)
Badge 8 through Elite Four - 163 Total Pokémon
- Gift in Mt. Mortar B1F: Tyrogue & one evolution (157 total)
- Route 34: Breed Tyrogue's evolution to get two Tyrogue, and evolve them into the other two evolutions (159 total)
- Walking on Route 27: Doduo, Dodrio (161 total)
- Walking on Route 27: Ponyta, Rapidash (163 total)
Elite Four through Badge 16 - 194 Total Pokémon
- Walking on Route 10: Electabuzz (164 total)
- Walking in Rock Tunnel 1F: Cubone, Marowak (166 total)
- Walking in Rock Tunnel B1F: Kangaskhan (167 total)
- Walking on Route 7: Houndour, Houndoom (169 total)
- Walking on Route 7: Murkrow (170 total)
- Walking on Route 16: Grimer, Muk (172 total)
- Walking on Route 16: Slugma, Magcargo (174 total)
- Purchase in Celadon Game Corner: Porygon (175 total)
- Walking on Route 14: Chansey, Blissey (177 total)
- In-game Trade on Route 14: Aerodactyl: Trade your Chansey (178 total)
- Static encounter in Vermilion City: Snorlax (179 total)
- Walking in Diglett's Cave: Diglett, Dugtrio (181 total)
- Walking on Route 2: Pikachu (182 total)
- Walking in Mt. Moon: Clefairy (183 total)
- Evolve two Moon Stone Pokémon with Moon Stones from the Clefairy event in Mt. Moon (185 total)
- Walking on Route 21: Mr. Mime (186 total)
- Route 34: Breed Electabuzz to get Elekid (187 total)
- Route 34: Breed Pikachu to get Pichu (188 total)
- Route 34: Breed Clefairy or Clefable to get Cleffa (189 total)
- Static encounter on Bell Tower 10F: Ho-Oh (190 total)
- Evolve a Leaf Stone Pokémon with a Leaf Stone from Bill's grandfather on Route 25 (191 total)
- Evolve a Water Stone Pokémon with a Water Stone from Bill's grandfather on Route 25 (192 total)
- Evolve a Fire Stone Pokémon with a Fire Stone from Bill's grandfather on Route 25 (193 total)
- Evolve a Thunderstone Pokémon with a Thunderstone from Bill's grandfather on Route 25 (194 total)
Badge 16 through defeating Red - 199 Total Pokémon
- Walking on Route 28: Sneasel (195 total)
- Walking in Mt. Silver 2F and item rooms: Misdreavus (196 total)
- Walking in Mt. Silver 1F, 2F, Summit, and item rooms: Larvitar, Pupitar, Tyranitar (199 total)