Group size estimator

How many trainers do I need to invite?

The Estimator is already "trainers of this attacker needed to finish inside the timer", so this page does not invent a number: it reads it off the boss's own ranked counter list for three realistic parties and re-simulates each of them at every level from 20 to 50.

Raid bossTierIVsWeatherFriendshipDodgingShadow attackersMega attackersLegendary attackers

Invite 4 to be safe — 3 if everyone is prepared

At level 40, a party of Gyarados's top six counters needs 2.37 trainers (round up: 3), and a mixed lobby of ranks 13-24 needs 3.25 (round up: 4). The raid timer is 300 seconds and one prepared trainer alone would take 11:13. No level in this range makes it soloable with a prepared party.

Gyarados · Shadow Tier 5

waterflying

Weak to

electricrock

Boss CP: 43,756
Boss HP: 15,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Gyarados at each attacker level
Attacker level	Six of the best counter	A prepared party	A mixed local group	Prepared solo time	Faints per timer
Level 20	4(3.68)	4(3.86)	6(5.05)	18:15	6.0
Level 25	4(3.05)	4(3.20)	5(4.27)	15:07	6.0
Level 30	3(2.55)	3(2.72)	4(3.72)	12:51	6.0
Level 35	3(2.38)	3(2.54)	4(3.50)	11:59	6.0
Level 40	3(2.24)	3(2.37)	4(3.25)	11:13	6.0
Level 45	3(2.11)	3(2.27)	4(3.13)	10:44	6.0
Level 50	3(2.04)	3(2.17)	4(3.01)	10:15	6.0

Whole trainers in bold, the raw estimator in brackets — 2.04 means two trainers is right on the line and three is comfortable.

Six of the best counter

Every trainer brings six copies of the single best counter — the theoretical floor.

3 trainers at level 40

Zeraora2.24

A prepared party

Each trainer brings the boss's top six counters, powered up and correctly TM'd.

3 trainers at level 40

Zeraora2.24
Thundurus (Therian)2.35
Zekrom2.36
Regieleki2.33
Xurkitree2.39
Raikou2.58

A mixed local group

Ranks 13-24: reasonable but unoptimised parties, which is what a public lobby usually is.

4 trainers at level 40

Thundurus (Incarnate)2.97
Vikavolt3.10
Jolteon3.11
Mewtwo3.09
Kyurem (Black)3.14
Toxtricity3.16

The party these numbers assume

1. Zeraora

Volt Switch + Plasma Fists

2. Thundurus (Therian)

Volt Switch + Wildbolt Storm

3. Zekrom

Charge Beam + Fusion Bolt

4. Regieleki

Thunder Shock + Thunder Cage

5. Xurkitree

Thunder Shock + Discharge

6. Raikou

Thunder Shock + Wild Charge

See the full ranked counter list for Gyarados · check a real lobby (win chance, who brings what) · make a share card of the top six

How this is worked out

The boss is ranked once at level 40 with rankCached (the same memoised call /raids makes), then the three bands — rank 1, ranks 1-6, ranks 13-24 — are re-simulated at each attacker level with an 8-run Monte Carlo each. Holding the party fixed and moving only its level is deliberate: it answers "what if my party were level 20" rather than "what would a level-20 player's completely different party be", and it is about ten times cheaper than re-ranking every attacker seven times. The Estimator itself is Pokebattler's definition, time to win including rejoin time divided by the raid timer.