Legalább egy füldugó kell.

Legalább means at least.

It is placed first here because Hungarian word order often puts the most important or contrastive information early. In this sentence, the speaker is emphasizing the minimum requirement: at least one earplug.

So:

• Legalább egy füldugó kell. = The minimum needed is one earplug.

You could move legalább in some contexts, but the version given is very natural and puts clear focus on the minimum amount.

Egy can mean both a/an and one, depending on context.

Here it clearly means one, because it is modified by legalább:

• legalább egy = at least one

Without legalább, egy füldugó could sometimes be understood more like an earplug, depending on context. But in this sentence, the number sense is strong.

Because Hungarian is counting one item:

• egy füldugó = one earplug

After a numeral like egy, the noun stays in the singular in Hungarian. This is normal:

• egy könyv = one book
• két könyv = two books
• három füldugó = three earplugs

So even after numbers greater than one, Hungarian usually keeps the noun in the singular form.

Also, Hungarian is treating füldugó as one item. In real life, earplugs often come as a pair, but grammatically this sentence is just talking about one unit.

Kell means is needed, is necessary, or must be depending on context.

In this sentence:

• egy füldugó kell = one earplug is needed

Hungarian often uses kell in a very compact way where English might use need, be necessary, or be required.

So this sentence is not missing anything. It is a complete sentence.

A few similar examples:

• Pénz kell. = Money is needed.
• Idő kell. = Time is needed.
• Csend kell. = Silence is needed.

Because Hungarian does not always use an explicit verb corresponding to English is in the present tense.

Also, in this sentence the main verb is already kell, so there is no need for another verb.

English says:

• At least one earplug is needed.

Hungarian says:

• Legalább egy füldugó kell.

The idea of is needed is expressed by kell alone.

By itself, Legalább egy füldugó kell. is impersonal or general. It means something like:

• At least one earplug is needed
• You need at least one earplug
• At least one earplug is required

The person is not stated.

If you want to say who needs it, Hungarian often adds a dative pronoun:

• Nekem legalább egy füldugó kell. = I need at least one earplug.
• Neked legalább egy füldugó kell. = You need at least one earplug.
• Neki legalább egy füldugó kell. = He/she needs at least one earplug.

So the basic sentence is general, and the person can be added if needed.

Hungarian word order is fairly flexible, but different orders change the emphasis.

The given sentence:

• Legalább egy füldugó kell.

puts focus on the minimum amount.

Other versions may be possible in the right context, for example:

• Egy füldugó kell legalább.
• Füldugó kell legalább egy. — much less natural in ordinary speech
• Legalább egy füldugóra van szükség. — a different structure, more formal

So yes, word order can change, but the original version is natural and clear.

Yes. Füldugó is a compound noun:

• fül = ear
• dugó = plug, stopper

So füldugó literally means something like ear-plug.

Hungarian forms many everyday nouns this way. Learning to spot compounds is very helpful.

Yes. A common alternative is:

• Legalább egy füldugóra van szükség.

This also means At least one earplug is needed or There is need for at least one earplug.

The difference is mainly style and structure:

• Legalább egy füldugó kell. = shorter, very common, direct
• Legalább egy füldugóra van szükség. = slightly more formal or explicit

Notice that with szükség van, the noun takes the -ra/-re ending:

• füldugó → füldugóra

Because it is functioning as the thing that is needed, and with kell that noun often appears in the basic dictionary form, with no extra case ending.

Compare:

• Füldugó kell. = An earplug is needed.
• Pénz kell. = Money is needed.
• Segítség kell. = Help is needed.

But if you use a different structure, the noun may take a case ending:

• Füldugóra van szükség. = There is need for an earplug.

So the lack of an ending is normal for this kell pattern.

It is natural Hungarian.

Depending on context, it could mean:

• At least one earplug is needed.
• You need at least one earplug.
• At least one earplug is required.

It would sound normal in situations like instructions, shopping, travel, concerts, sleeping, or safety advice.

If the speaker wants to sound more specific, they might add who needs it or what it is for, but the sentence itself is perfectly natural.