Hindi pa kasya sa akin ang maliit na sukat, kaya hahanapin ko ang mas malaking sukat.

Filipino often puts the predicate first, not the subject.

So in:

Hindi pa kasya sa akin ang maliit na sukat

the part Hindi pa kasya sa akin comes first, and ang maliit na sukat comes later.

A very literal breakdown is something like:

• Hindi pa = not yet
• kasya = fit / be the right size / have enough room
• sa akin = for me / on me
• ang maliit na sukat = the small size

So the sentence structure is normal Filipino word order: predicate first, then the ang-phrase.

Kasya usually means to fit, to have enough room, or to be the right size.

In clothing contexts, it means something like:

• fit me
• be the right size for me
• have enough room for me

So Hindi pa kasya sa akin ang maliit na sukat means the small size still does not fit the speaker.

You may also hear kasya in other situations, for example:

• Kasya ba ang limang tao sa kotse?
  = Can five people fit in the car?
• Hindi kasya ang pera ko.
  = My money is not enough.

So kasya has a broader idea of enough space / enough size / enough capacity.

Pa here means still or yet, depending on the translation.

So:

• Hindi kasya = does not fit
• Hindi pa kasya = does not fit yet / still does not fit

It adds the idea that the situation continues up to now.

This is very common in Filipino:

• Hindi pa ako kumakain. = I haven’t eaten yet.
• Wala pa siya. = He/She isn’t here yet.
• Hindi pa tapos. = It’s not finished yet.

In your sentence, pa suggests the speaker has tried the small size, and it still is not right.

Sa akin is used because kasya takes an oblique phrase with sa for the person affected.

So Filipino says:

• Kasya sa akin = fits me
• Kasya sa iyo = fits you
• Kasya sa kanya = fits him/her

This is more natural than using ako here.

Compare:

• Ako = I / me as a subject-like pronoun
• Sa akin = to me / for me / on me

With kasya, the usual pattern is:

kasya + sa + person

Examples:

• Kasya sa akin ang damit. = The clothes fit me.
• Hindi kasya sa kanya ang sapatos. = The shoes do not fit him/her.

Ang maliit na sukat is the ang-marked phrase, which is the focused noun phrase in the sentence.

It means the small size.

Breakdown:

• ang = marker for the focused noun phrase
• maliit = small
• na = linker
• sukat = size

So:

• maliit na sukat = small size

In this sentence, that whole phrase is the thing being talked about as the item that does not fit.

The na / -ng linker connects modifiers and the words they describe.

Here, maliit and malaki are adjectives modifying sukat.

So:

• maliit na sukat = small size
• malaking sukat = big/large size

Why does one use na and the other use -ng?

• If the first word ends in a consonant, use na
  
  • maliit na sukat
• If the first word ends in a vowel, n, or ng, use -ng attached to the first word
  
  • malaking sukat

More examples:

• magandang bahay = beautiful house
• mabait na bata = kind child

They do the same grammatical job.

Here kaya means so, therefore, or that’s why.

It connects the two ideas:

1. The small size does not fit yet.
2. Therefore, the speaker will look for a bigger size.

So:

Hindi pa kasya sa akin ang maliit na sukat, kaya hahanapin ko ang mas malaking sukat.

= The small size still doesn’t fit me, so I’ll look for a bigger size.

Be careful: kaya can mean different things in different contexts. For example:

• Kaya ko. = I can do it.
• kaya as a connector = so / therefore

In your sentence, it is the connector meaning.

Hahanapin is the future aspect of hanapin.

Root verb:

• hanap = search/look for

Verb form here:

• hanapin = look for something
• hahanapin = will look for something

This form focuses on the thing being looked for.

So:

• Hahanapin ko ang mas malaking sukat.
  = I will look for the bigger size.

This is an object-focus form. The thing being sought is ang mas malaking sukat.

Compare:

• Maghahanap ako ng mas malaking sukat.
  = I will look for a bigger size.

That version is also natural, but the grammar focus is a bit different.

It comes from the root hanap.

A simplified way to see it:

• root: hanap
• object-focus infinitive/base form: hanapin
• future: hahanapin

The future aspect is formed by reduplicating the first syllable of the root:

• ha
  • hanapin → hahanapin

Similar patterns:

• bili → bibilhin = will buy
• kuha → kukunin = will get/take
• basa → babasahin = will read

So hahanapin ko means I will look for it or I will look for [something].

Ko is a short pronoun meaning I / my / me, depending on the structure.

In this sentence:

Hahanapin ko ang mas malaking sukat

• hahanapin = will look for
• ko = by me / I
• ang mas malaking sukat = the bigger size

So ko marks the actor here, while ang mas malaking sukat is the focused noun phrase.

Short pronouns like ko, mo, niya often appear early in the clause, usually after the verb or predicate.

That is why ko comes right after hahanapin.

Mas is used for comparison. It means more.

So:

• malaki = big / large
• mas malaki = bigger / larger
• mas malaking sukat = a bigger size / the bigger size

In natural English, we say bigger, but Filipino often uses mas + adjective instead of changing the adjective itself.

Examples:

• mas maliit = smaller
• mas maganda = more beautiful / prettier
• mas mabilis = faster

So ang mas malaking sukat literally means the more large size, but naturally it means the bigger size.

Because the comparison is understood from the context.

The speaker has already mentioned:

• ang maliit na sukat = the small size

Then in the next clause they say:

• ang mas malaking sukat = the bigger size

So Filipino does not need to say than the small size explicitly here. The listener naturally understands that the speaker wants a size bigger than the small one.

If you wanted to make a comparison more explicit in other contexts, Filipino can use structures with kaysa:

• Mas malaki ito kaysa roon.
  = This is bigger than that.

But in your sentence, mas malaking sukat is enough.

Sukat means size or measurement, and it is commonly used for clothing size.

Examples:

• Anong sukat mo? = What’s your size?
• Maliit na sukat = small size
• Malaking sukat = large size

But sukat can also refer more generally to measurements or dimensions, depending on context.

In clothing stores, though, sukat is a very natural word.

Sometimes laki can refer to size in a general sense, but for clothing or product sizes, sukat is usually the clearer and more natural choice.

Compare:

• malaking sukat = larger size
• malaki ang laki is not how you would normally say this

For shopping, clothes, shoes, and similar items, sukat is the better word.

Because both clauses are built with verbs/predicates that naturally take an ang-marked focused noun phrase.

First clause:

• Hindi pa kasya sa akin ang maliit na sukat.

Second clause:

• Hahanapin ko ang mas malaking sukat.

In the second clause, hahanapin is object-focus, so the thing being looked for is marked with ang.

If you changed the verb to an actor-focus form like maghahanap, then you would usually use ng instead:

• Maghahanap ako ng mas malaking sukat.

Both are correct, but the verb form and the case marker change together.

Yes. Even though the meaning is already known, it helps to know that several English translations are possible.

Possible natural translations include:

• The small size still doesn’t fit me, so I’ll look for a bigger size.
• The small size isn’t big enough for me yet, so I’ll look for a larger size.
• The small size doesn’t fit me, so I’m going to find a bigger one.

This shows that Filipino expressions do not always match English word-for-word. For example:

• kasya may become fit, be enough, or have room
• mas malaking sukat may become bigger size or larger size

It sounds natural and standard. It is perfectly fine in everyday speech.

That said, in casual spoken Filipino, people might also say something simpler like:

• Hindi pa kasya sa akin ang small, kaya maghahanap ako ng mas malaking size.

This mixes English loanwords like small and size, which is very common in real conversation.

Your original sentence is more fully Filipino and is still completely natural.