Ritengo utile questo piano.

Ritengo is the first-person singular present tense of ritenere.

In this sentence, it means something like:

• I consider
• I deem
• I find

So Ritengo utile questo piano means I consider this plan useful.

Compared with penso (I think) or credo (I believe), ritengo sounds a bit more formal and deliberate.

Italian often drops subject pronouns when they are not needed.

The ending -o in ritengo already tells you the subject is I.

So:

• Ritengo utile questo piano = normal
• Io ritengo utile questo piano = possible, but adds emphasis, contrast, or formality

For example, io might be used if you want to stress my opinion in contrast with someone else’s.

It is the present indicative.

Here it usually means:

• I consider
• I think
• I find

Depending on context, the present tense can describe a current opinion or a general stance.

Utile is an adjective meaning useful.

It agrees with the noun it refers to, but in the singular, its form is the same for both masculine and feminine:

• un piano utile = a useful plan
• una soluzione utile = a useful solution

In the plural, it becomes:

• utili

So:

• piano utile
• soluzione utile
• piani utili
• soluzioni utili

In your sentence, utile refers to questo piano.

In this sentence, utile is not simply part of a noun phrase like a useful plan. It is functioning as a predicate adjective after ritengo, expressing the judgment made about questo piano.

So the structure is roughly:

ritengo + utile + questo piano
= I consider + useful + this plan

Italian also allows:

Ritengo questo piano utile.

That version is also correct and may feel clearer to learners because the object comes before the adjective.

The version you were given, Ritengo utile questo piano, is perfectly natural and puts slightly more focus on utile.

Yes. Questo piano is the direct object of ritengo.

What is being considered useful?
Questo piano.

Meanwhile, utile is the quality assigned to that object.

So the sentence works like:

• object: questo piano
• judgment about it: utile

Because in Italian, demonstratives like questo usually already do the job that the article would do.

So you say:

• questo piano = this plan
• not il questo piano

That is normal Italian.

Yes, ritenere is somewhat formal or elevated, especially compared with everyday alternatives.

Some less formal or more common alternatives are:

• Trovo utile questo piano. = I find this plan useful.
• Penso che questo piano sia utile. = I think this plan is useful.
• Credo che questo piano sia utile. = I believe this plan is useful.

So ritengo is common, but it sounds especially at home in:

• professional language
• academic writing
• formal speech
• careful argumentation

Yes, absolutely.

That version uses a full clause:

• Ritengo utile questo piano
• Ritengo che questo piano sia utile

Both are correct.

The difference is mainly stylistic:

• Ritengo utile questo piano is more compact and direct.
• Ritengo che questo piano sia utile is more explicit and clause-based.

After ritenere che, standard Italian normally uses the subjunctive, so sia is the expected form.

No, not in this structure.

You say:

• ritenere qualcosa utile
• ritenere qualcuno capace
• ritenere che...

So there is no preposition before utile or before questo piano here.

Yes.

You can say:

• Lo ritengo utile.

Here, lo replaces questo piano.

This is very common in Italian. Notice that the direct object pronoun goes before the verb:

• Lo ritengo utile
• not Ritengo lo utile

Because piano is a masculine singular noun in this meaning.

So you get:

• questo piano

If the noun were feminine singular, you would use questa:

• questa idea
• questa soluzione

So questo helps show the gender and number of piano.

Yes, very often.

You could say:

• Considero utile questo piano.

This is very close in meaning to Ritengo utile questo piano.

In many contexts, considerare may feel a little more straightforward for English speakers because it looks like consider.
However, Italian ritenere is also very common and often sounds slightly more formal or thoughtful.