Datamined BaseCaptureRates for every Pokemon GO Pokemon currently obtainable in game. The numbers are base, meaning before you throw any Pokeballs or use any items such as Razz Berries. As reported by The_Desert_Rain (/r/TheSilphRoad), his tests yielded these results for the capture rates and capture rates per level. Check this link for more details and in depth analysis.

It’s currently unclear how and at what % does Nice/Great/Excellent throw affect these numbers. The general formula that’s used to determine the average capture rate is the following: Capture Rate = 0.5 * Base Capture Rate / CP MultiplierOverall, even the basic evolutions are not a good choice for capture farming and are prone to lose a lot of PokeBalls.

Base Capture Rate Unevolved 1st, Evolution 2nd, Evolution
56% Magikarp
48% Oddish
40% Caterpie, Weedle, Pidgey, Rattata, Spearow, Ekans, Sandshrew, Nidoran♀, Nidoran♂, Jigglypuff, Zubat, Venonat, Diglett, Meowth, Psyduck, Mankey, Poliwag, Abra, Machop, Bellsprout, Tentacool, Geodude, Slowpoke, Magnemite, Doduo, Seel, Grimer, Shellder, Drowzee, Krabby, Voltorb, Exeggcute, Koffing, Rhyhorn, Horsea, Goldeen, Staryu
32% Paras, Ponyta, Gastly, Cubone, Tangela, Eevee, Porygon, Omanyte, Kabuto, Dratini
24% Clefairy, Vulpix, Gloom, Growlithe, Farfetch’d, Mr., Mime, Scyther, Jynx, Electabuzz, Magmar, Pinsir, Tauros
20% Metapod, Kakuna, Pidgeotto, Nidorina, Nidorino, Poliwhirl, Kadabra, Machoke, Weepinbell, Graveler
16% Bulbasaur, Charmander, Squirtle, Pikachu, Hitmonlee, Hitmonchan, Lickitung, Chansey, Lapras, Ditto, Aerodactyl, Snorlax Raticate, Fearow, Arbok, Sandslash, Wigglytuff, Golbat, Parasect, Venomoth, Dugtrio, Persian, Golduck, Primeape, Tentacruel, Slowbro, Magneton, Dodrio, Dewgong, Muk, Cloyster, Haunter, Onix, Hypno, Kingler, Electrode, Exeggutor, Weezing, Kangaskhan, Rhydon, Seadra, Seaking, Starmie
12% Vileplume, Rapidash, Marowak, Vaporeon, Jolteon, Flareon, Omastar, Kabutops
10% Butterfree, Beedrill, Pidgeot, Nidoqueen, Nidoking, Poliwrath, Alakazam, Machamp, Victreebel, Golem
8% Ivysaur, Charmeleon, Wartortle, Raichu, Clefable, Ninetales, Arcanine, Gyarados, Dragonair Gengar
4% Venusaur, Charizard, Blastoise, Dragonite
0% Articuno, Zapdos, Moltres, Mewtwo, Mew