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Balloon quantity calculator
How many balloons it takes to fill a room — or a car — comes down to volume: your space times a 0.9 fill factor, divided by the helium each balloon holds. An 11-inch latex balloon takes about 0.5 cubic feet of helium, a 9-inch about 0.3, and a 36-inch giant about 7.5. Pick the space, set the three dimensions, choose the balloon size and your tank, and the calculator returns a balloon count, the helium it consumes, and how many tanks that takes — disposable tanks fill roughly 30 eleven-inch balloons each, so anything past a few dozen points you at a rental cylinder. Float time is built into the note: latex runs 10–12 hours indoors untreated, so inflation timing matters as much as the count.
Live calculator
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Your estimate
Results
Usable box × 0.9 fill factor; packing gaps can swing the real count ±15%.
Partner pick
Balloon pumpCounts done — a pump fills garlands and arches fast, no helium needed.Check current price ↗As an Amazon Associate, CalcForged earns from qualifying purchases.The math, plainly
How it works
- 01
The usable space is your length × width × height, times a 0.9 fill factor for the corners and odd volumes the tidy box leaves out.
- 02
Each balloon size has a known helium appetite — about 0.5 cu ft for an 11-inch latex — and the count is usable volume divided by that number.
- 03
Helium volume divides by your tank size and rounds up, because a tank that dies two balloons short ruins the reveal; float times come from standard latex charts.
Try a real scenario
Fill a sedan with 11-inch balloons
InputsCar interior 4 × 5 × 3 ft, 11 in balloons, 14.9 cu ft disposable tank
ResultAbout 108 balloons — 54 cu ft of helium, or 4 disposable tanks (one 55 cu ft rental covers it).
Gear for the job
Tools & materials people actually buy
Balloon pump
A hand or electric pump fills arches and garlands in minutes — air-filled ones never float anyway.
Arch strip kit
The plastic strip and glue dots that turn loose balloons into a professional arch or garland.
Helium regulator
A good regulator and nozzle save helium and fingers on every fill.
As an Amazon Associate, CalcForged earns from qualifying purchases made through these links.