Kontraktor memperkirakan biaya tenaga kerja dan biaya bahan bangunan.

Indonesian does not use articles like a, an, or the.

So kontraktor can mean:

• a contractor
• the contractor
• contractors in some contexts

The exact meaning depends on context. In this sentence, English might naturally translate it as The contractor estimates... or A contractor estimates... depending on the situation.

Memperkirakan means to estimate, to predict, or to approximate, depending on context.

In this sentence, because it is followed by costs, the most natural meaning is to estimate:

• Kontraktor memperkirakan biaya... = The contractor estimates the cost...

It comes from the root kira, which is related to estimating, guessing, or thinking approximately.

This is a very common learner question, because Indonesian often adds prefixes and suffixes to a root word.

Here, the core root is:

• kira = estimate, guess, reckon

Then it becomes:

• perkiraan = an estimate / estimation
• memperkirakan = to estimate

You do not need to fully analyze every affix at the beginning, but it helps to recognize that Indonesian often builds verbs this way. In practice, it is best to learn memperkirakan as a whole verb meaning to estimate.

Word by word:

• biaya = cost, expense
• tenaga kerja = labor, workforce

So:

• biaya tenaga kerja = labor cost or labor costs

A more literal breakdown of tenaga kerja is:

• tenaga = energy, power, labor force
• kerja = work

But together, tenaga kerja is a fixed expression meaning labor or workforce.

This means building material cost or cost of building materials.

Breakdown:

• biaya = cost
• bahan = material, ingredient
• bangunan = building
• bahan bangunan = building materials / construction materials

So:

• biaya bahan bangunan = the cost of building materials

This is a noun phrase where one noun modifies another, which is very common in Indonesian.

Good question. Indonesian often repeats a noun to make the structure clearer and more balanced.

So:

• biaya tenaga kerja dan biaya bahan bangunan

clearly means:

• labor costs and building material costs

If you say:

• biaya tenaga kerja dan bahan bangunan

it could still be understood, but it sounds less parallel and may suggest:

• the cost of labor and building materials

That version is also possible in some contexts, but repeating biaya makes it extra clear that there are two categories of costs.

In Indonesian noun phrases, the main noun usually comes first, and the describing noun comes after it.

So:

• biaya tenaga kerja = cost [of] labor
• bahan bangunan = materials [for] building / building materials

This is the opposite of typical English order, where the describing noun often comes first:

• labor cost
• building materials

A useful pattern to remember is:

• head noun + modifier

Examples:

• rumah sakit = hospital
• buku pelajaran = textbook
• biaya sekolah = school costs

Indonesian nouns usually do not change form for singular and plural.

So biaya can mean:

• cost
• costs
• expense
• expenses

Context tells you which one sounds best in English.

In this sentence, English often uses the plural:

• labor costs and building material costs

But depending on style, you might also translate it as:

• the cost of labor and building materials

Both are reasonable.

Indonesian often connects nouns directly without needing a separate word like of.

So:

• biaya tenaga kerja literally looks like cost labor
• but it means cost of labor

Likewise:

• bahan bangunan = materials for building / building materials

English often needs words like of, for, or a noun used adjectivally, but Indonesian usually just places the nouns together.

Yes. Dan is the standard word for and.

In this sentence, it joins two noun phrases:

• biaya tenaga kerja
• biaya bahan bangunan

So the structure is:

• Kontraktor = subject
• memperkirakan = verb
• biaya tenaga kerja dan biaya bahan bangunan = object

Yes. Because Indonesian is often less specific than English about articles and number, several translations are possible:

• The contractor estimates labor costs and building material costs.
• A contractor estimates labor and building material costs.
• The contractor estimates the cost of labor and building materials.

All of these can fit the Indonesian sentence, depending on context.

A very natural shorter version would be:

• Kontraktor memperkirakan biaya tenaga kerja dan bahan bangunan.

This often means:

• The contractor estimates labor and building material costs.

The original sentence with biaya repeated is not wrong at all. It is just a little more explicit and symmetrical. That can be especially useful in formal or technical contexts.