Learn Hardcore Spanish (Spain): Estoy contentísimo con mi nuevo portátil.

In Spanish, estar is used for temporary states, emotions, and conditions, while ser is used for more permanent characteristics, identity, and origin.

Being contentísimo (extremely happy) is an emotional state, not a permanent trait, so you use estar:

Estoy contento = I am (feeling) happy.
Soy feliz = I am (a) happy (person) – suggests a more general trait.

So Estoy contentísimo is correct because you are talking about how you feel right now about your new laptop, not about what you are like as a person.

What exactly does contentísimo mean compared to contento or muy contento?

All three express happiness, but at different intensities:

Estoy contento = I’m happy.
Estoy muy contento = I’m very happy.
Estoy contentísimo = I’m extremely / super / really, really happy.

-ísimo is a suffix that adds the sense of “very, extremely”. It usually sounds a bit more expressive or emphatic than muy contento, and sometimes a little more informal or enthusiastic, depending on tone and context.

How is contentísimo formed? Are there rules for adding -ísimo?