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 2 to be safe — 2 if everyone is prepared

At level 40, a party of Mega Tatsugiri's top six counters needs 1.30 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 1.66 (round up: 2). The raid timer is 300 seconds and one prepared trainer alone would take 6:03. No level in this range makes it soloable with a prepared party. A duo works from level 25.

Mega Tatsugiri · Mega

dragonwater

Weak to

dragonfairy

Boss CP: 41,299
Boss HP: 9,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Mega Tatsugiri 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	2(1.83)	3(2.06)	3(2.53)	9:34	6.0
Level 25	2(1.27)	2(1.79)	3(2.22)	8:18	6.0
Level 30	2(1.16)	2(1.46)	2(1.83)	6:48	5.9
Level 35	2(1.09)	2(1.35)	2(1.74)	6:15	5.8
Level 40	2(1.07)	2(1.30)	2(1.66)	6:03	5.7
Level 45	2(1.00)	2(1.27)	2(1.60)	5:53	5.5
Level 50	2(1.00)	2(1.22)	2(1.52)	5:40	5.4

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.

2 trainers at level 40

Eternatus1.07

A prepared party

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

2 trainers at level 40

Eternatus1.07
Palkia (Origin)1.30
Baxcalibur1.33
Rayquaza1.35
Kyurem (Black)1.38
Dialga (Origin)1.39

A mixed local group

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

2 trainers at level 40

Kyurem (White)1.56
Haxorus1.58
Dialga1.60
Zacian (Crowned Sword)1.63
Zekrom1.67
Kyurem1.67

The party these numbers assume

1. Eternatus

Dragon Tail + Dynamax Cannon

2. Palkia (Origin)

Dragon Tail + Spacial Rend

3. Baxcalibur

Dragon Breath + Glaive Rush

4. Rayquaza

Dragon Tail + Breaking Swipe

5. Kyurem (Black)

Dragon Tail + Freeze Shock

6. Dialga (Origin)

Dragon Breath + Roar of Time

See the full ranked counter list for Mega Tatsugiri · 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.