You should evolve Nidorino into Nidoking in FireRed as soon as you have a Moon Stone, with most guides suggesting doing it before around level 23 so you do not miss any useful early‑game moves or power spikes.

Quick Scoop: Best Time to Evolve Nidorino in FireRed

In PokĂ©mon FireRed, Nidoran♂ evolves into Nidorino at level 16 automatically.

After that, Nidorino evolves into Nidoking with a Moon Stone, and level itself does not matter for the evolution.

Most modern guides and forum-style discussions agree on this simple rule:

  • Evolve Nidoran♂ into Nidorino at level 16 (don’t delay this).
  • Evolve Nidorino into Nidoking as soon as you get a Moon Stone , typically well before level 23.

Once it becomes Nidoking, you get a large stat boost and far better use of TMs like Earthquake, Thunderbolt, Ice Beam, and Flamethrower compared with keeping it as a Nidorino for many levels.

Many older suggestions to “wait until level 43 for Horn Drill” are now considered overkill, since Nidoking’s higher stats and TM coverage are more valuable than a late one-hit KO move in regular FireRed playthroughs.

Simple example strategy

  1. Catch Nidoran♂ early on.
  2. Let it evolve into Nidorino at level 16.
  3. Grab your first Moon Stone (for example from the hidden rock in Cinnabar’s PokĂ©mon Mansion in FireRed) and evolve Nidorino immediately to Nidoking.
  1. Build its moveset with strong TMs as you progress.

This way, your Nidoking carries you through most of the game instead of waiting with a weaker Nidorino.

Information gathered from public forums or data available on the internet and portrayed here.