Я взял рулетку, чтобы измерить длину стены и ширину окна.

Взял is the perfective past form of взять. It presents the action as a single completed event: the speaker took/picked up the tape measure.

Брал would be imperfective and would sound more like:

• he was taking it,
• he used to take it,
• or the action is being described without focusing on completion.

In this sentence, the idea is: first he took the tape measure, then he used it for a purpose. So взял is the natural choice.

Here рулетка means a tape measure.

This is a very common Russian word for the retractable measuring tape used in construction or around the house.

Be aware that рулетка can also mean roulette in some contexts, but in this sentence, because of измерить длину стены и ширину окна, it clearly means a measuring tape.

Чтобы introduces a purpose clause. It means something like:

• so that
• in order to

So:

Я взял рулетку, чтобы измерить...
= I took a tape measure in order to measure...

This is one of the most common ways in Russian to express purpose.

Измерить is the perfective infinitive. It means to measure completely / to get the measurement.

That fits the sentence well, because the goal is to finish the measuring:

• measure the wall’s length,
• measure the window’s width.

If you used измерять, that would be the imperfective infinitive, which focuses more on the process or repeated activity. In a purpose clause like this, Russian often prefers the perfective when the goal is a completed result.

So:

• чтобы измерить = in order to measure (and get the result)
• чтобы измерять = more like in order to be measuring / to measure regularly, which does not fit as well here

They are in the accusative because they are the direct objects of измерить.

You measure what?

• длину
• ширину

Base forms:

• длина → длину
• ширина → ширину

Both are feminine nouns, so their accusative singular ends in -у.

Because they are not the direct objects of the verb.

The direct objects are:

• длину
• ширину

Then стены and окна depend on those nouns:

• длина стены = the length of the wall
• ширина окна = the width of the window

So стены and окна are in the genitive case, because Russian commonly uses:

• длина чего? = the length of what?
• ширина чего? = the width of what?

This is a very important pattern in Russian:

• цвет машины = the color of the car
• конец фильма = the end of the film
• ширина дороги = the width of the road

Not if you want the same meaning.

Измерить стену и окно would mean measure the wall and the window, but it would be less specific about what dimension is being measured.

The original sentence says specifically:

• the length of the wall
• the width of the window

Russian often expresses this with:

• измерить длину чего-либо
• измерить ширину чего-либо
• измерить высоту чего-либо

So the sentence is more precise than just измерить стену и окно.

Because one verb can govern both objects:

измерить длину стены и ширину окна

This is exactly like English:

• to measure the length of the wall and the width of the window

Russian does not need to repeat the verb unless the speaker wants extra emphasis or clarity.

Yes, Russian word order is fairly flexible, though the given sentence is the most neutral and natural.

The original order: Я взял рулетку, чтобы измерить длину стены и ширину окна.

This is neutral: action first, purpose second.

You could also say: Чтобы измерить длину стены и ширину окна, я взял рулетку.

That puts more focus on the purpose: In order to measure the length of the wall and the width of the window, I took a tape measure.

Both are grammatical. The difference is mainly emphasis and style.

Russian has no articles like the or a/an.

So Russian simply says:

• стена = wall / the wall / a wall
• окно = window / the window / a window

The exact meaning depends on context. In this sentence, English naturally uses the wall and the window, but Russian does not need separate words for that.

Yes, very often.

Померить is a common, everyday verb meaning to measure. In casual speech, many Russians would say:

Я взял рулетку, чтобы померить длину стены и ширину окна.

Difference in tone:

• измерить = a bit more neutral, standard, sometimes slightly more formal or technical
• померить = more conversational

Both are correct here.

Because the sentence is talking about:

• the length of one wall
• the width of one window

So Russian uses singular genitive:

• стены = of the wall
• окна = of the window

If it were plural, you would get different forms, for example:

• длину стен = the length of the walls
• ширину окон = the width of the windows

By itself, я взял mainly tells you that the action of taking happened and was completed.

Whether the speaker still has the tape measure depends on context. In this sentence, the likely meaning is:

• he took/picked up the tape measure for immediate use.

So the focus is on the completed action of grabbing it, not necessarily on the continuing possession.