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 5 to be safe — 4 if everyone is prepared

At level 40, a party of Tornadus (Therian)'s top six counters needs 3.36 trainers (round up: 4), and a mixed lobby of ranks 13-24 needs 4.31 (round up: 5). The raid timer is 300 seconds and one prepared trainer alone would take 15:29. No level in this range makes it soloable with a prepared party.

Tornadus (Therian) · Elite

flying

Weak to

rockelectricice

Boss CP: 51,103
Boss HP: 20,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Tornadus (Therian) 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	5(4.67)	6(5.41)	7(6.65)	24:53	6.0
Level 25	5(4.10)	5(4.41)	6(5.43)	20:18	6.0
Level 30	4(3.57)	4(3.88)	5(4.79)	17:52	6.0
Level 35	4(3.20)	4(3.58)	5(4.54)	16:30	6.0
Level 40	3(2.98)	4(3.36)	5(4.31)	15:29	6.0
Level 45	3(2.83)	4(3.22)	5(4.12)	14:49	6.0
Level 50	3(2.71)	4(3.09)	4(3.94)	14:13	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

Kyurem (White)2.98

A prepared party

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

4 trainers at level 40

Kyurem (White)2.98
Kyurem (Black)3.26
Zeraora3.35
Xurkitree3.45
Thundurus (Therian)3.56
Zekrom3.58

A mixed local group

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

5 trainers at level 40

Rhyperior4.04
Rampardos4.05
Necrozma (Dawn Wings)4.11
Necrozma (Dusk Mane)4.13
Electivire4.15
Zacian (Crowned Sword)4.22

The party these numbers assume

1. Kyurem (White)

Ice Fang + Ice Burn

2. Kyurem (Black)

Dragon Tail + Freeze Shock

3. Zeraora

Spark + Plasma Fists

4. Xurkitree

Thunder Shock + Discharge

5. Thundurus (Therian)

Volt Switch + Wildbolt Storm

6. Zekrom

Charge Beam + Fusion Bolt

See the full ranked counter list for Tornadus (Therian) · 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.