About the Balloon Arch and Garland Calculator
This balloon calculator works out how many balloons you need for a party arch or garland and how much helium a set of floating balloons will take. Enter the garland length — or the width and height of an arch — choose a classic cluster arch or a loose organic garland, and it returns the balloon count with a spare allowance for pops.
It is made for parents planning a birthday, event planners quoting a balloon wall, and DIY decorators buying a garland kit who want to know whether 100 balloons is really enough. For helium, enter how many 11-inch latex and 18-inch foil balloons will float and the size of your tank to see how many tanks to buy.
Arch length is measured along the curve, treating the arch as a half-ellipse from ground to ground. Cluster spacing and garland density are typical decorator figures; real counts vary with how big you inflate each balloon, so build in the spare allowance. Arches and garlands are normally air-filled — only the floating balloons need helium.
With the default inputs, the balloons to buy for the arch/garland is 159. Change any value above to recalculate instantly.
How to use the balloon arch and garland calculator
- 1Choose a garland or an arch and enter its length, or width and height.
- 2Pick an organic garland or a classic cluster arch.
- 3Adjust fullness or cluster spacing to match the look you want.
- 4Keep a 10% spare allowance for pops.
- 5Enter any helium floaters and your tank size to see how many tanks to buy.
Formula and method
For an arch, the balloons follow the curve, so the calculator measures the length of a half-ellipse whose base is the arch width and whose height is the arch height, using Ramanujan’s perimeter approximation. A garland length is used as entered.
A classic arch is built from identical clusters (usually four 11-inch balloons) placed about one balloon-width apart, so the count is the length in inches divided by the spacing, rounded up, times balloons per cluster. Organic garlands mix sizes and are estimated per foot (about 8, 12 or 16 balloons per foot). A spare allowance covers pops and uneven sizing. Helium assumes about 0.5 cu ft per 11-inch latex and per 18-inch foil balloon.
- W, H
- Arch base width and height (ft)
- spacing
- Distance between cluster centres (in)
- spare
- Extra allowance for pops (%)
Worked examples
12 ft organic garland with a few floaters
At a standard 12 balloons per foot, a 12 ft garland needs 144 balloons; adding 10% spare gives 159. Twelve 11-inch floaters and three 18-inch foils need about 7.5 cu ft of helium — one 14.9 cu ft tank.
Classic 8 × 8 ft arch with quad clusters
An 8 ft wide, 8 ft tall arch is about 19.4 ft (232.5 in) along the curve. With a cluster every 10 inches that is 24 clusters of 4, or 96 balloons; 10% spare makes 106. No helium is needed for an air-filled arch.
20 ft quint-cluster garland plus 60 helium balloons
Twenty feet is 240 inches; at 9-inch spacing that rounds up to 27 clusters of 5, or 135 balloons, and 142 with 5% spare. Fifty latex and ten foil floaters need about 30 cu ft of helium, just over two 14.9 cu ft tanks — so buy three.
Frequently asked questions
How many balloons do I need for a balloon arch?+
A typical 8 ft wide by 8 ft tall classic arch is about 19 ft along the curve and needs around 100 eleven-inch balloons in clusters of four. An organic arch of the same size uses roughly 150–250 mixed balloons depending on fullness.
How many balloons per foot for a garland?+
Organic garlands use about 8 balloons per foot for a light, airy look, around 12 for a standard look and 15–18 for a lush, full garland. Classic quad-cluster garlands with 11-inch balloons use about 5 per foot.
How much helium does an 11-inch balloon need?+
An 11-inch latex balloon takes roughly 0.5 cubic feet of helium, as does an 18-inch foil balloon. A 14.9 cu ft disposable tank therefore fills about 30 eleven-inch balloons.
Do balloon arches need helium?+
No. Most arches and garlands are filled with air and attached to a frame, a strip or a wall, which is cheaper and lasts days instead of hours. Only freestanding floating balloons need helium.
How long do helium balloons float?+
Untreated 11-inch latex balloons usually float for around 8–12 hours, while foil balloons can float for several days. A liquid sealant inside latex balloons can extend float time considerably.