How to calculate number of balloons for a balloon drop

I need to fill a net with the following dimensions: 10 meters long by 5 meters wide, and 1 meter deep. How many 11 inch balloons do I need? Is there a formula to use for filling a balloon net?

ANSWER

I found an example calculation from filling a room with balloons. It's probably not a 100% correct, but close enough...

(Volume of room) / (volume of balloon) * 1/2

So, in your case...

Volume of net in cubic feet: 1765
Volume of a fully inflated 11 inch balloon in cubic feet: 0.41

(1765*0.41)*0.5 = 2152

So you'd need roughly 2150 balloons to fill your net.

That's also about the same number I deducted from looking at this large balloon drop net.

The cylindrical net has a volume of about 358 cubic feet and holds 500 x 11 inch balloons. Your net's volume is almost 5 times as big.
(The image I uploaded shows such a cylindrical balloon drop net.)

So you need about 5 times as many balloons (= 2500).

Depending on how tight you want to pack your net, and whether you want to under inflate your balloons slightly to prevent them from popping, you'd need between 2200 and 2400 balloons.