Vacuum packing for travel: how much space do you really save?

Vacuum bags have lived in wardrobes for years, storing winter duvets. The travel version is newer: a smaller bag that goes in your suitcase, and a pump small enough to come with you, so you can compress again for the trip home. The promise is that your clothes take up half the space. Here is what that means in practice.

Why clothes compress at all

Much of the volume of a folded jumper is air trapped between the fibres. Remove the air and the fabric itself takes very little room. That is why soft, fluffy items shrink dramatically and dense items barely change.

What compresses well

• Puffer and down jackets: the biggest win, because they are mostly air.
• Hoodies, fleeces and knitwear: large savings.
• T-shirts, underwear and socks: moderate savings each, but they add up because you pack so many.

What does not compress much

• Jeans and heavy cotton trousers: dense fabric with little air in it.
• Shoes, toiletries and electronics: these should never go in a vacuum bag.
• Structured clothes: blazers and stiff-collared shirts come out creased. More on that in does vacuum packing damage clothes.

So how much do you save?

With a typical mix of travel clothes, expect the packed bag to shrink to about half its volume. The bag in the Airlock Travel Kit holds about 20 litres: roughly 10 T-shirts, or 6 light jackets, or 4 hoodies, or 2 puffer jackets. A bag full of puffers shrinks more than that, a bag full of jeans less.

In a cabin-size suitcase, that can be the difference between a week of clothes and room left for an extra pair of shoes, or between paying for a checked bag and not.

How to pack a compression bag properly

1. Fold flat or roll tightly. Loose, bulky folds trap air and leave creases.
2. Do not overfill. An overstuffed bag strains the zip and will not seal well.
3. Close the zip fully. Run your fingers along it twice. A small gap is the most common reason a bag will not hold its vacuum.
4. Pump through the valve. With the Airlock pump, place it on the valve and press once. Its 5000 Pa of suction does the rest.
5. Smooth it as it shrinks. Flatten the bag with your hands while the pump runs so it compresses evenly into a flat block.

Packing for the return trip

This is where a travel kit beats roll-up bags that you squeeze by hand. On the way home your clothes are worn, often bulkier, and you may have bought something. A rechargeable pump lets you compress just as well in a hotel room as at home. The Airlock pump lasts about 14 trips per charge, so you will not need to bring a charger on a normal holiday.

The catch: volume, not weight

A compressed bag takes less space but weighs exactly the same. If you fill the space you saved, your suitcase gets heavier. How to stay within airline limits is covered in vacuum bags and airline weight limits.