Balloon Calculator
Find out how many balloons a helium tank will fill and what each one costs.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Helium tanks are rated in cubic feet, and a standard 11 inch latex balloon holds about half a cubic foot of gas. That single number is what lets you compare the price of a tank against buying pre-inflated balloons, which is where the real saving usually is.
Worked example
calculated with the default values below
Helium tank size 14.9 cu ft (medium) · Balloon size 11 inch · Cost of the tank 45 $ · Balloons per pack 50 · Cost per balloon pack 12 $ Balloons per tank 29 · Total to fill one tank 57.00 $ · Helium per balloon 0.500 cu ft · Cost per filled balloon 1.966 $ · Balloon packs needed 1
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
v = 0.5 × (s ÷ 11)³; N = ⌊V ÷ v⌋
- s
- Balloon size, in
- v
- Helium per balloon, ft³
- V
- Tank capacity, ft³
- N
- Balloons per tank
An 11-inch balloon needs 0.5 ft³ as the baseline; tank capacity and per-balloon volume use the same units.
Frequently asked questions
Why does the model assign 0.5 cubic foot of helium to an 11-inch balloon?
The calculator assumes 0.5 cubic foot for an 11-inch balloon and scales that volume by (diameter ÷ 11)^3. On this assumption, a 16-inch balloon uses about 1.54 cubic feet, so the same tank fills fewer large balloons. Actual fill volume varies with balloon shape and how fully it is inflated; 0.5 cubic foot is a model input, not an exact physical requirement.