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 Chesnaught's top six counters needs 1.13 trainers (round up: 2), and a mixed lobby of ranks 13-24 needs 1.43 (round up: 2). The raid timer is 300 seconds and one prepared trainer alone would take 5:15. No level in this range makes it soloable with a prepared party. A duo works from level 20.

Mega Chesnaught · Mega

grassfighting

Weak to

flyingpoisonfirepsychicicefairy

Boss CP: 42,017
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 Chesnaught 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(1.36)	2(1.70)	3(2.12)	7:54	6.0
Level 25	2(1.18)	2(1.40)	2(1.81)	6:30	6.0
Level 30	2(1.05)	2(1.24)	2(1.60)	5:46	6.0
Level 35	2(1.01)	2(1.18)	2(1.52)	5:28	5.9
Level 40	1(0.97)	2(1.13)	2(1.43)	5:15	5.9
Level 45	1(0.91)	2(1.09)	2(1.38)	5:03	5.9
Level 50	1(0.88)	2(1.05)	2(1.33)	4:53	5.8

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.

1 trainer at level 40

Rayquaza0.97

A prepared party

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

2 trainers at level 40

Rayquaza0.97
Moltres1.14
Yveltal1.14
Enamorus (Incarnate)1.16
Toucannon1.18
Galarian Articuno1.18

A mixed local group

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

2 trainers at level 40

Honchkrow1.34
Lugia1.33
Galarian Moltres1.39
Galarian Zapdos1.44
Flamigo1.43
Tornadus (Incarnate)1.44

The party these numbers assume

1. Rayquaza

Air Slash + Dragon Ascent

2. Moltres

Wing Attack + Fly

3. Yveltal

Gust + Oblivion Wing

4. Enamorus (Incarnate)

Fairy Wind + Fly

5. Toucannon

Peck + Beak Blast

6. Galarian Articuno

Psycho Cut + Fly

See the full ranked counter list for Mega Chesnaught · 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.