Pokémon Database

Pokémon Red, Blue and Yellow Catch Rate Calculator

Exact catch chance for every ball and status in Kanto. Generation I capture formula.

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Kanto's original games use the oldest and strangest catch system in the series. Instead of one formula, a throw has to get past two separate random checks, and the ball you pick changes how large the first roll is. This calculator walks through every possible first roll to give you the exact chance for any of the 151 Pokémon.

Select Pokémon

#025PikachuelectricPikachu

Catch rate and max HP start from the species data and a typical stat spread. Edit either one if you know your target's real value.

Battle Conditions

Results — Per Throw

Catch Probability37.9%
Visual
Decent
X value (internal)129
Ball multipliern/a
Current HP65 / 65
Ball roll range0 – 255
Status allowance0
Throws for 50%2
Throws for 95%7

Cumulative Catch Probability

1 throw
37.9%
3 throws
76.0%
5 throws
90.8%
10 throws
99.1%
20 throws
100%
50 throws
100%

How catching works in Generation I

Generation I uses two separate checks instead of one formula. First the game rolls a random number whose range depends on the ball: 0 to 255 for a Poké Ball, 0 to 200 for a Great Ball and 0 to 150 for an Ultra Ball. Sleep and freeze subtract 25 from that roll and the other status conditions subtract 12. If the result is below zero the Pokémon is caught on the spot, and if it is above the species' catch rate the throw fails.

Throws that pass the first check face an HP check. The game works out F as the target's max HP times 255, divided by 8 (12 for a Great Ball), divided by a quarter of its current HP, capped at 255. A second roll from 0 to 255 must not exceed F. Lower HP raises F, so weakening the target helps, but only on the second check.

Tips for Catching Pokémon in Pokémon Red, Blue and Yellow

  • Sleep and freeze are worth far more here than any later game. They remove 25 from the first roll, so a sleeping target can be caught outright on roughly one throw in ten before HP even matters.
  • A Great Ball rolls from 0 to 200 and an Ultra Ball from 0 to 150, which makes the first check easier to pass. The Great Ball also divides by 12 instead of 8 in the HP check, which slightly weakens that second check.
  • Dropping a target to the red zone matters because the HP check divides by a quarter of current HP. Getting to single-digit HP is the single biggest swing after status.
  • The Safari Zone uses different rules (bait, rocks and Safari Balls) and is not modeled here.

Ball Reference (Pokémon Red, Blue and Yellow)

Poké Ball
1×. No bonus.
Great Ball
1.5×. Reliable early upgrade.
Ultra Ball
2×. Best general-purpose ball.
Master Ball
Always catches.

Frequently Asked Questions

Why is the Master Ball the only guaranteed catch?

Every other ball can lose either the ball roll or the HP check. The Master Ball skips both and always succeeds.

Are Generation I catch rates the same as later games?

For most Pokémon yes, but a few differ. If you know the Red/Blue value for a species, type it into the catch rate box and the odds will update.

Does this work for Yellow too?

Yes. Red, Blue and Yellow share the same catching code, so the results are identical across all three versions.

More Catch Rate Calculators

Planning a playthrough? Read our Pokémon Red, Blue and Yellow guide.

Results are exact for the formula shown, to within the game's own rounding. Species catch rates are the current values and a few differ in older games, so edit the catch rate if you know yours.