This depends on the size (shape, too) and weight of the balloons. A good rule of thumb is that a liter of Helium will lift around a gram – or 1000 liters of gaseous Helium to lift a kilogram. (This is calculated subtracting the helium density from the air density of 1.204 g/L – 0.179 g/L) = 1.025 g/L net lift.
Estimating a not-to-small party balloon (11-inches in diameter) to hold about the same net lifting helium (Except for the weight of the balloon) as a 10-inch sphere of standard pressure (1 atm): It will lift about 8.6 grams since the volume of a sphere this size is about 8.6 liters. A 100-pack of my inexpensive commercial 11-inch party ballons weigh very close to 12 ounces which comes out to about 3.4 grams each.
So the net lift of one 11-party balloon is the helium lift minus the balloon’s weight:
8.6g-3.4g = 5.2 grams.
Let’s call it 5 grams even as you will probably have things like string or a tape of some sort to tie or connect things to the balloon. A kilogram is 1000 grams, so 1000/5 = 200 balloons will be required to lift the kilogram.
If you use bigger balloons the weight of the balloons and strings which in this example consumes nearly 42% of the helium’s lift can be cut down to only about 10-15% loss. But those would be 5 or 6 foot ballons which cost up to $15 each. With 100-200 of those filled with helium, a full grown man, his lawn chair, and many gallons of water can float up to nearly 15,000 feet and possibly the next state/country, as Kent Couch of Oregon has demonstrated. That is a 75-100 kilogram payload. Each ballon has a net lift of between 1 kilogram and 2 1/2 kilograms depending on the optimal fill amount.
to lift a 150 lb person ~
If you were using an average Amusement Park balloon containing approximately 14 liters of helium, you would need about 4852 balloons…Thats a lot of balloons!
How many helium balloons does it take to lift a 5 stone person ~
1 stone = 14lbs
5 stone = 70 pounds.
80 balloons lifts 1 lb
5600 balloons needed!
How Many Helium Balloons Would It Take To Lift An Average Person Off The Ground…?
6,000 to 7,000 ballons according to the Mythbusters show on the discovery channel.
Tip _ Someone accually did it !!! Read all about it !!
True Story ~~ Legacy of Lawnchair Larry !! ~~
Kent Couch of Oregon flew 193 miles on a lawn chair attached to helium balloons, emulating the startling 1982 flight over San Pedro by the late Larry Walters. Here’s the AP story on Couch, and an old Daily Breeze story on Walters. His experience was marked by mishaps, like dropping the pellet gun he needed to shoot balloons to descend, but Walters reached 16,000 feet and was spotted by airline pilots before landing in power lines in Long Beach. He paid a $1,500 fine to the FAA, and when asked why he did it quipped, “A man can’t just sit around.” Walters committed suicide in 1993.