How Much Helium Do You Need for Balloons?

September 7, 2026

The answer depends on two things: the size of your balloons and how long you need them to float. A 9in latex balloon takes about half a cubic foot of helium, a 12in takes roughly a cubic foot, and an 18in foil balloon takes about the same again.

Tanks in the UK are sold by cubic feet of gas, so once you know the balloon size the maths is straightforward. Below are the numbers for the tank sizes you can actually buy or hire here, plus float times and rough costs.

Worth saying before you spend anything: helium is only necessary for balloons that need to rise. Arches, garlands and table clusters are all air-filled and last far longer.

How many balloons each tank fills

Finding the right cylinder size suits anyone organising a home party or a larger venue celebration. Use these capacities to match your guest list and venue size, ensuring you do not run out of gas halfway through decorating. A helpful tip is to choose a slightly larger tank than you think you need, as a little helium always escapes during the learning curve of filling your first few balloons.

Small disposable tank (about 8 cu ft): 20 to 30 x 9in latex, or 10 to 12 x 18in foil.
Medium disposable tank (about 14 cu ft): 40 to 50 x 9in latex, or 20 x 18in foil.
Large disposable tank (about 30 cu ft): 80 to 100 x 9in latex.
Hired D-size cylinder (about 110 cu ft): around 250 x 9in latex.
Hired E-size cylinder (about 200 cu ft): around 450 x 9in latex.
Rule of thumb: 9in latex needs 0.4 cu ft, 11in needs 0.5, 12in needs 0.8, 18in foil needs 0.5.

How long helium balloons float

This guide suits early-bird party planners who want to get ahead with their decorating schedule. Understanding these timings helps you decide when to inflate your balloons so they look fresh for the arrival of your guests. As a practical tip, always store your filled balloons in a room with a steady, moderate temperature, avoiding cold garages and hot conservatories to maximise their float times.

9in latex: 5 to 7 hours. Fine for an evening, not for a whole day.
11in latex: 12 to 20 hours.
12in latex: up to 24 hours.
18in foil: 3 to 5 days, sometimes a week.
Latex treated with Hi-Float: 2 to 4 days for about 5p a balloon.
Cold rooms shorten float time; a warm car on the way to the venue shortens it badly.

What it costs in the UK

This financial breakdown suits budget-conscious party hosts who are deciding between doing it themselves and hiring professional help. Use these average prices to compare your options when planning a birthday party, wedding, or anniversary celebration. Our practical tip is to check whether your local card shop offers an inflation service, as this can sometimes be more cost-effective than buying a disposable cylinder for small gatherings.

Small disposable tank: £25 to £35, including the balloons in most kits.
Medium disposable tank: £40 to £50.
Large disposable tank: £60 to £75.
Hired cylinder: £40 to £70 for the gas plus a deposit, usually a week's hire.
Pre-inflated balloons from a shop: £2 to £4 each for latex, £6 to £12 for a large foil.
Air-filled arch instead: about £25 for 130 balloons, strip and glue dots.

When you don't need helium at all

This alternative approach suits creative decorators looking to save money and create displays that last for days. Use air-filled designs when you are decorating a large space or setting up your venue the day before. A practical tip is to invest in a cheap hand pump and some balloon tape, which makes constructing impressive structures surprisingly quick and simple without any expensive gas.

Balloon arches and garlands — always air-filled, they hold shape better.
Table clusters on weighted sticks, which look neater than floating bunches anyway.
Balloon walls and backdrops behind a photo corner.
Letter and number foils on a wall rather than floating.
Outdoor decorations, where floating balloons blow into hedges within the hour.
Anything you're building the day before — air stays put, helium doesn't.

Key things to remember

Inflate latex on the day, foils the night before.
Buy 10% more gas than the calculation says — you'll over-inflate a few.
If nothing needs to float, skip helium entirely and go air-filled.

Frequently asked questions

How much helium do you need for 50 balloons?

For 50 x 9in latex balloons you need about 20 cubic feet, so a large disposable tank or a hired cylinder. A medium 14 cu ft tank will only get you to around 40.

How many balloons does a small helium tank fill?

A standard small disposable tank holds about 8 cubic feet, which fills 20 to 30 x 9in latex balloons or 10 to 12 x 18in foil balloons.

How long do helium balloons last?

9in latex floats for 5 to 7 hours, 12in for up to 24, and 18in foil balloons for 3 to 5 days. Treating latex with Hi-Float extends it to 2 to 4 days.

How much does helium cost in the UK?

£25 to £35 for a small disposable tank, £60 to £75 for a large one, or £40 to £70 plus a deposit to hire a cylinder for a week.

Should you inflate helium balloons the day before?

Only foil balloons. Standard 9in latex will have sunk before the party starts, so inflate latex on the day — ideally within a few hours of guests arriving.

Is there an alternative to helium balloons?

Yes, and it's usually better. Air-filled garlands, arches, balloon walls and weighted table clusters cost a fraction as much, last for days and don't escape to the ceiling.

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