How much helium do you need for balloons?

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

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

How long helium balloons float

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

What it costs in the UK

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

When you don't need helium at all

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

Birthday cards to go with the party

Designed in house, printed and posted in the UK.

Milestone birthday cards

The big-number designs for the guest of honour.

How to write it so it lands

• 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.

Where to shop next

• Happy birthday banners
• Cake toppers
• Table confetti
• Party bag fillers
• Buy party supplies
• Balloon arch ideas
• How to use a balloon arch kit
• How to make bunting
• How to hang bunting
• Party bag ideas for kids
• What to put in a party bag
• Birthday party ideas
• Milestone birthday cards
• Buy a birthday card online
• All birthday cards
• How to make a balloon arch
• Photo booth prop ideas
• Party bag ideas for adults

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.