How does the catch rate formula work in Pokemon Gold and Silver?

Original Gold and Silver use the Generation II catch formula: start from the species catch rate, apply the ball multiplier, then for most balls compute floor((3×MaxHP − 2×CurrentHP) × rate / (3×MaxHP)), add sleep/freeze (+10), clamp to 255, and succeed if a random 0–255 roll is less than or equal to that value.

Do burn, poison, and paralysis help catch rates in Gold and Silver?

They were intended to add +5, but a cartridge bug means only sleep and freeze add +10. Burn, poison, and paralysis give no catch bonus on original Gold and Silver.

Do Moon Ball and Fast Ball work as described?

No. Moon Ball is bugged and never multiplies. Fast Ball only multiplies for Magnemite, Grimer, and Tangela (the first three SometimesFleeMons entries), not all flee species. Love Ball boosts same-species same-gender pairs instead of opposite gender.

Does Level Ball use HP or status in Gen 2?

Level Ball multiplies the base catch rate by 2, 4, or 8 from the level comparison, then skips the HP and status steps entirely. Chip damage and sleep do not improve Level Ball odds on original Gold and Silver.

Pokemon Gold and Silver Catch Rate Calculator - Gen 2 Ball Odds Tool

Gen 2 catch math · Original GBC · not HGSS

Pokemon Gold & Silver catch rate calculator

Estimate real cartridge odds for every ball in original Gold and Silver: species catch rate, HP factor, sleep/freeze, Ultra/Great, and Kurt specials with the famous Gen 2 bugs called out. Presets jump to Ho-Oh, Lugia, roaming beasts, Red Gyarados, and Snorlax.

Gen 2 cartridge formula Sleep / freeze +10 Burn / PSN / PAR buggy +0 251 species Kurt ball bugs modeled Not HGSS

Fast answer

Chip HP → sleep → best ball → throw

For legendaries with catch rate 3, Ultra Ball + sleep at ~1 HP is the standard plan on original GBC. Kurt’s Level Ball can beat Ultra when your lead is much higher level—but it ignores HP and status. Heavy Ball helps Snorlax and other heavy mon. Open the presets, then jump to the matching catch guide and Catch checklist to log the entry.

—Final catch a

—Per-ball chance

—Expected balls

—Wobble outlook

Interactive tool

Catch odds workbench

Mark caught Craft Kurt balls

Search species Wild Pokémon

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Wild level Your lead level

HP DV (for max HP) HP Stat Exp

Current HP % (10%)

Current HP Max HP

Lock current/max HP (stop auto from % and level) Ball Status Fishing battle (Lure Ball ×3) Love Ball same-species same gender (bugged boost)

Chance per throw

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Final catch value a

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Notes

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Ball comparison (same HP & status)

Open species in Pokédex Log on Catch checklist

Ball reference

Shop balls & Kurt specials on original G/S

Items · Ultra Ball Apricorn trees

Ball	Modifier	On original Gold/Silver	Best use
Master Ball	Always catches	Works	Roamers if you want zero risk
Ultra Ball	×2 catch rate	Works	Default legendary ball
Great Ball / Park Ball	×1.5	Works	Mid-game / Bug Contest
Poke Ball / Friend Ball	×1 (Friend sets friendship 200)	Works	Friend Ball for happiness evolutions
Level Ball	×2 / ×4 / ×8 by level gap; skips HP & status	Works	Overleveled lead vs weak wilds
Lure Ball	×3 on fishing battles	Works	Rod lines · Dratini / Magikarp
Heavy Ball	−20 / +0 / +20 / +30 / +40 by weight	Works	Snorlax, Gyarados, Steelix-tier weight
Fast Ball	Intended ×4 on flee mons	Bugged · Magnemite / Grimer / Tangela only	Almost never worth farming for roamers
Moon Ball	Intended ×4 Moon Stone lines	Bugged · always ×1	Collection only
Love Ball	Intended opposite gender	Bugged · same gender ×8	Niche breeding setups

Formula

What the cartridge actually does

Core pipeline

rate = species catch rate rate = ball_multiplier(rate) if ball ≠ Level Ball: load 16-bit 3M and 2H if 3M > 255: shift both right twice keep the low byte of each term numerator = (low8(3M) − low8(2H)) mod 256 a = low8(floor(rate × numerator / low8(3M))) if a = 0: a = 1 if sleep/freeze: a += 10 else: a = rate // no HP, no status status overflow saturates a to 255 catch if Random(0–255) ≤ a

Chance is exactly (a + 1) / 256. The low-byte path is why Max HP above 341 can produce broken, non-monotonic odds; a zero divisor can lock the cartridge routine. Master Ball short-circuits to a guaranteed catch.

Status bug (real G/S)

Sleep or freeze: +10 after the HP step.
Burn / poison / paralysis: intended +5, but the status check is buggy—+0 on cart.
This tool models the buggy cartridge by default.

Heavy Ball weights

< 102.4 kg: rate −20 (floor 1)
< 204.8 kg: +0
< 307.2 kg: +20
< 409.6 kg: +30
≥ 409.6 kg: +40

Snorlax (~460 kg) gets the full +40 before the HP formula.

Level Ball boundaries

The engine compares the wild level against floor(lead/2) and then floor(lead/4). Odd lead levels therefore do not behave like a simple “lead > 2× / 4× wild” floating-point test. The calculator uses the cartridge’s integer shifts.

Save before the encounterEspecially Red Gyarados, statics, and roamers. Prefer sleep or freeze+10 that actually works on G/S. Chip without KOFalse swipe / chip to low HP when you can. Stock Ultra BallsDefault for rate-3 legendaries. Check Kurt optionsLevel / Heavy / Lure when conditions fit. Log the catchUse Catch checklist + Progress planner.

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Play tips

Using odds on a real Gold/Silver run

Ho-Oh & Lugia (rate 3)

Expect long Ultra Ball + sleep sessions even at 1 HP. Master Ball is valid if you saved it. Full path: legendary guide.

Roaming beasts

Raikou / Entei / Suicune also rate 3 and can flee. Mean Turn / trapping moves and mean Ultra stock matter more than Fast Ball (bugged). Track routes in Mechanics Lab.

Red Gyarados

Rate 45 at Lv.30—much friendlier than legendaries. Still save first; it is a one-shot shiny moment. Lake of Rage guide.

Snorlax & Heavy Ball

At ~460 kg, Heavy Ball’s +40 is huge before the HP step. Pair with sleep after the Poké Flute wake sequence. Snorlax guide.

Sudowoodo

One static on Route 36 after SquirtBottle. Rate 65—Great Balls are fine, but do not KO if you want the Rock body. SquirtBottle path.

Friend Ball + happiness

Catch rate is only ×1, but friendship starts at 200—excellent for Espeon/Umbreon and Crobat paths. See friendship checker.

FAQ

Common catch questions

Is this the HeartGold / SoulSilver formula?

No. This page models original Game Boy Color Gold and Silver only. Remakes change some ball behavior and encounter setups—keep HGSS guides separate.

Why do my Ultra + sleep odds still look low on Ho-Oh?

Catch rate 3 is intentionally brutal. Even with Ultra (×2 → 6), full chip, and +10 sleep, final a sits in the teens—roughly mid-single-digit percent per ball. That is correct, not a tool error.

Should I use Fast Ball on Raikou?

Not for catch rate. Fast Ball’s boost only applies to Magnemite, Grimer, and Tangela on original G/S. Roamers need Ultra / Master strategies and the roaming tracker in Mechanics Lab.

Where do I get more Ultra Balls?

Department stores and late Johto/Kanto marts stock them. Check the shops tool and Ultra Ball item page.

How do I log progress after a catch?

Use the Catch checklist for Seen/Caught flags and the Progress planner for story gates. Species pages live under Pokédex.

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