Learn Hardcore Portuguese (Portugal): Se eu tivesse mais paciência, teria explicado tudo com mais calma. - If I had more patience, I would have explained everything more calmly.

Tivesse is the imperfect subjunctive of ter, and it’s the standard form used in Portuguese in hypothetical / unreal "if" clauses about the past or about situations that are not real.

Se eu tivesse mais paciência...
= If I had more patience (but I didn’t / don’t).

If you said:

Se eu tinha mais paciência...

this would sound wrong or very odd in standard European Portuguese in this kind of hypothetical sentence. You normally need the subjunctive (here: tivesse) after se when you’re expressing an unreal or contrary‑to‑fact condition.

What tense is teria explicado, and how is it formed?

Teria explicado is the conditional perfect (also called past conditional).

It’s formed with:

ter in the conditional (teria, terias, teria, teríamos, teriam)
the past participle of the main verb (explicado)

So:

teria explicado = would have explained
teria feito = would have done
teria dito = would have said

In this sentence, teria explicado refers to an unreal action in the past: explaining that did not happen (or did not happen in that calmer way).

What kind of conditional sentence is Se eu tivesse mais paciência, teria explicado tudo com mais calma?

It’s a counterfactual conditional about the past:

Condition (unreal): Se eu tivesse mais paciência
Result (unreal past result): teria explicado tudo com mais calma

In English this corresponds to:

If I had had more patience, I would have explained everything more calmly.

It talks about something that did not happen (you didn’t have enough patience, and you didn’t explain things calmly).

Can I reverse the order of the two clauses?

Yes. You can say:

Se eu tivesse mais paciência, teria explicado tudo com mais calma.
Teria explicado tudo com mais calma se eu tivesse mais paciência.

Both are correct. The meaning is the same.
When the if‑clause (se‑clause) comes first, it’s standard to put a comma after it. When it comes second, the comma is usually omitted:

Se eu tivesse mais paciência, teria explicado tudo com mais calma.
Teria explicado tudo com mais calma se eu tivesse mais paciência.

Why is there a comma after Se eu tivesse mais paciência?

In Portuguese, when a dependent clause (like a conditional clause with se) comes before the main clause, it’s normally separated by a comma:

Se eu tivesse mais paciência, teria explicado tudo com mais calma.
Quando eu cheguei, ele já tinha saído.
Se chover, não vamos sair.

If you invert the order and put the main clause first, the comma is usually not used:

Teria explicado tudo com mais calma se eu tivesse mais paciência.
Não vamos sair se chover.

Could I say Se eu tivesse mais paciência, explicaria tudo com mais calma instead?

Yes, that’s also correct, but it slightly changes the time reference and nuance.

Se eu tivesse mais paciência, explicaria tudo com mais calma.
→ More like: If I had more patience, I would explain everything more calmly (in general / now / habitually).
Se eu tivesse mais paciência, teria explicado tudo com mais calma.
→ More like: If I had had more patience (in that specific situation), I would have explained everything more calmly.

So:

explicaria (simple conditional) often refers to a present or general unreal situation.
teria explicado (conditional perfect) refers to a past unreal situation.

What’s the difference between Se eu tivesse mais paciência and Se eu tivesse tido mais paciência?

Both can be correct, but there’s a nuance:

Se eu tivesse mais paciência, teria explicado tudo com mais calma.
- Focus on a general quality: If I were a more patient person / if I had more patience (as a trait), I would have explained…
Se eu tivesse tido mais paciência, teria explicado tudo com mais calma.
- Focus on that particular moment or episode: If I had had more patience (then, at that time), I would have explained…

So tivesse can suggest a more general lack of patience, while tivesse tido zooms in on a specific situation in the past.

Why is paciência a noun ("patience") but in English we say "If I had been more patient"?

Portuguese often uses nouns where English prefers adjectives:

ter paciência = to have patience
ter mais paciência = to have more patience / be more patient

So:

Se eu tivesse mais paciência…
~ If I had more patience / If I had been more patient…

You could technically use the adjective paciente:

Se eu fosse mais paciente…

This is also correct and close to English: If I were more patient…
But ter (mais) paciência is extremely common and very idiomatic.

What exactly does com mais calma mean, grammatically?

Com mais calma is a prepositional phrase used adverbially to describe how the explaining would be done:

com = with
mais = more
calma = calm / calmness

Literally: with more calm(ness)
Functionally: more calmly.

So:

teria explicado tudo com mais calma
≈ would have explained everything more calmly.

It’s very natural in Portuguese to use com + noun as an adverbial phrase:

falar com cuidado = to speak carefully
agir com pressa = to act in a hurry
responder com calma = to answer calmly

Could I say teria explicado tudo mais calmamente instead of com mais calma?

Yes, mais calmamente is also grammatically correct:

Teria explicado tudo mais calmamente.

However, in everyday European Portuguese, com mais calma sounds more natural and idiomatic than mais calmamente, which is a bit more formal or bookish.

So both are possible, but:

com mais calma → more common in speech and informal writing
mais calmamente → correct, but less frequent in casual conversation

Does se always require the subjunctive, like tivesse, in Portuguese?

No, se does not always require the subjunctive. It depends on the type of condition:

Real / likely condition (indicative)
- Se tiver tempo, ligo‑te.
  If I have time, I’ll call you.
- Se chove, não saio.
  If it rains, I don’t go out.
Unreal / hypothetical condition (subjunctive)
- Se eu tivesse tempo, ligava‑te.
  If I had time, I would call you.
- Se eu tivesse mais paciência, teria explicado tudo com mais calma.
  If I had had more patience, I would have explained everything more calmly.

In your sentence, the situation is unreal / contrary to fact, so Portuguese uses the imperfect subjunctive (tivesse).

Is there a more colloquial European Portuguese version of this sentence?

Yes. In informal European Portuguese, people often mix se + imperfect subjunctive with a compound past in the indicative instead of a conditional perfect, for example:

Se eu tivesse mais paciência, tinha explicado tudo com mais calma.

Formally, grammar books prefer:

Se eu tivesse mais paciência, teria explicado tudo com mais calma.

But in everyday speech in Portugal, tinha explicado (or tinha explicado tudo com mais calma) is very common in this type of conditional, even though it’s not the "textbook" form.