The first thing you need from our balloon arch calculator is the formula for calculating the required length of line, as this determines the number of balloons you'll need for your arch.
You can also use these instructions when you want to know how many balloons you'll need for a balloon garland.
To figure out the size of the balloon arch you want to build, measure the height and width of the area where it will be displayed.
Use the following calculations to work out the approximate total length of your arch line or frame.
To make an arch that's wider than it is tall:
width + height = approximate total length.
For an arch that has the same height and width:
(1.5 x height) + width = approximate total length.
For an arch that's taller than it is wide:
(2 x height) + width = approximate total length.
Next, you want to calculate how many balloons you need. This depends on the type of balloon arch or garland you have in mind and the size of the balloons.
For a 'String of Pearls' arch (i.e a floating arch with a single row of balloons) you'll need about 3 x 11" balloons per meter (this translates into 0.91 x 11" balloons per foot).
Example: Let's say your arch is 6m (20') wide and 6.7m (22') high. As your arch is taller than wide, formula 3 from above applies to calculate the arch length:
(2 x 6.7m) + 6.0m = 13.4m + 6.0m = 19.4 m
So your arch is roughly 20m long, which means you need 60 x 11" balloons (20m x 3 balloons per meter).
If the length of the balloon arch or garland and the diameter of balloons are in the same units (both in ft, in, m, cm, mm ) you can use this formula for an arch with clusters of 4 balloons:
Divide the diameter of the balloon into the length of the arch and multiple by 4.8 to get the number of balloons needed (thanks to Sean O'Kelly from balloondecor.com.au who shared this formula with our readers).
Length of arch (unit)
-------------------------------- x 4.8 = number of balloons
Diameter of balloon (same unit)
You want to make an arch that is 6.1m (20') wide and 3.7m (12') high. You plan to use 11" balloons (28cm diameter). As your arch is wider than tall, formula 1 from above applies. We'll calculate everything in cm to stay with the same unit.
Arch length: 610cm + 370cm = 980cm
Number of balloons: 980cm / 28cm * 4.8 = 168 balloons
Number of 4 balloon clusters: 168 / 4 = 42
If you calculate everything in feet and inches, here's an easier way to estimate the number of balloons you need for a 4 balloon per cluster arch...
Is your head spinning from all these numbers and formulas? Fear not. I've calculated the number of balloons for various arch or garland lengths for you.
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