fill up

make something completely full, or become completely full

A2

What does "fill sth up" mean?

Fill up means to make something completely full, or for something to become completely full on its own. You can use it for containers like bottles, glasses, and tanks, or for spaces like rooms and car parks when they get crowded. It is also very common in British English when talking about putting fuel in a car — for example, stopping at a petrol station to fill up. The idea is always about reaching full capacity, whether you are adding water to a jug or watching a café get busy.

Examples

How to use it

fill up + container/space

The most common pattern — use it when something or someone fills a container or space completely.

Can you fill up the water bottle before we leave?

fill + object + up

The object can go between 'fill' and 'up', which is very natural with short nouns.

She filled the glass up and put it on the table.

fill + pronoun + up

When the object is a pronoun, it must go between 'fill' and 'up' — never after 'up'.

The tank is empty — can you fill it up?

subject + fill up (no object)

Use this pattern when you want to say a place or container becomes full by itself, without saying what fills it.

The car park fills up very quickly on weekday mornings.

fill up on + food

Use 'fill up on' to say someone eats a lot of a particular food.

We filled up on sandwiches before the long drive.

Common Collocations

fill up the carfill up the tankfill up a glassfill up the roomfill up with petrolfill up on food

Common Mistakes

Pronoun in the wrong place

When the object is a pronoun like 'it' or 'them', it must go between 'fill' and 'up'. Putting it after 'up' is incorrect.

✗ Can you fill up it before we go?
✓ Can you fill it up before we go?
Confusing 'fill up' with 'fill in'

'Fill in' is used for completing forms or blank spaces. 'Fill up' is about making something completely full with a substance or people — not for forms.

✗ Please fill up the application form.
✓ Please fill in the application form.

Usage

In British English, 'fill up' is the everyday expression for putting fuel in a car. It can be used without an object when the meaning is clear from context: 'I stopped to fill up on the way.'

Frequently Asked Questions

Can I say 'fill up' without saying what I'm filling?

Yes! 'Fill up' is often used without an object when the meaning is clear from the situation. For example, a driver might say 'I need to stop and fill up' without mentioning petrol. This is very natural in everyday spoken English.

Is 'fill up' used the same way in British and American English?

Both use 'fill up', but there is a small difference with cars. British speakers say 'fill up with petrol', while American speakers say 'fill up with gas'. For other contexts like bottles, rooms, or tanks, both varieties use it in the same way.

Can 'fill up' be used in the passive?

Yes, the passive is natural, especially when talking about containers, vehicles, or spaces. For example: 'The tank was filled up before the trip' or 'All the seats were filled up by noon'.

Does 'fill up' only work with liquids?

No — you can use 'fill up' with liquids, fuel, food, and even people in a space. You might fill up a tank with petrol, fill up a plate with food, or say that a room filled up with guests. The key idea is simply reaching full capacity.

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