Lo siento, ahora mismo estoy ocupado.

Literally, lo siento means I feel it:

• lo = it
• siento = I feel / I am sorry (from sentir)

In practice, Spanish uses lo siento as a standard way to say I’m sorry. You do not need to translate it word for word when learning the phrase.

Because siento comes from the verb sentir (to feel), not ser (to be).

• sentir → siento = I feel
• ser → soy = I am

So lo siento is an idiomatic expression based on feeling, not on being.

Ahora mismo means right now or at this very moment.

• ahora = now
• mismo adds emphasis, like right in right now

So compared with just ahora, ahora mismo sounds a bit more immediate.

Yes. Ahora estoy ocupado is perfectly correct and natural.

The difference is mainly emphasis:

• ahora = now
• ahora mismo = right now, at the moment

So ahora mismo makes it sound a little more specific or immediate.

Because Spanish uses estar for temporary states or conditions, and being busy is normally treated as temporary.

• estoy ocupado = I’m busy / I’m occupied
• soy ocupado would sound wrong in this context

As a rule of thumb, use estar for how someone is at the moment, and ser for more permanent identity or defining traits.

In this sentence, ocupado means busy.

Although ocupado is related to English occupied, the natural translation here is:

• estoy ocupado = I’m busy

Spanish often uses ocupado/ocupada where English would normally say busy.

Because Spanish often leaves out subject pronouns when the verb already shows who the subject is.

• estoy already means I am
• so yo estoy ocupado and estoy ocupado both mean I’m busy

Usually, Spanish omits yo unless you want emphasis, contrast, or clarity.

Because adjectives in Spanish usually agree with the gender of the person speaking.

• A man would usually say estoy ocupado
• A woman would usually say estoy ocupada

So the sentence changes depending on who is speaking.

In this sentence, Lo siento, ahora mismo estoy ocupado is completely natural.

Spanish word order is fairly flexible, so you may also hear:

• Lo siento, estoy ocupado ahora mismo

Both are correct. The version with ahora mismo earlier can sound slightly more immediate or frame the situation sooner.

Yes, it is polite and natural.

• Lo siento softens the message
• ahora mismo estoy ocupado explains the reason

It sounds like a courteous way to say you cannot do something at the moment. If you want to sound even softer, you could add something like pero luego te ayudo or ¿te parece si hablamos después?

Yes. It is neutral and works in both.

The sentence itself does not include tú or usted, so nothing in it makes it specifically informal or formal. It can be said to a friend, coworker, customer, or stranger depending on context.

A simple pronunciation guide is:

oh-koo-PAH-thoh

In much of Spain, the c before a is a normal k sound, and the d between vowels is often softened. Also, in most of Spain, the z sound appears only with z or c before e/i, so here there is no special th sound except if someone is giving a very approximate guide for the final do, which is better thought of as a soft doh.

A clearer learner-friendly breakdown is:

• o = like o in not for many accents
• cu = koo
• pa = PAH (this is the stressed syllable)
• do = doh

So: o-cu-PA-do.

Yes, but the tone changes slightly.

• Lo siento = I’m sorry
• Perdón = sorry / pardon me
• Disculpa = sorry / excuse me (informal singular)
• Disculpe = formal singular

Lo siento often sounds more like genuine regret.
Perdón and disculpa/disculpe can sound more like excuse me or a lighter apology, depending on context.