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Propane tank and cylinder sizing

Enter appliance input, the container type and the coldest temperature at the site. The calculator estimates how much vapor each container can deliver, how many you need and how long they last.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

Pre-sizing
Demand

HD-5 propane is at least 90% propane. Heating value on an HHV basis (21,548 Btu/lb), as appliance ratings.

Containers and site

Minimum pressure: the lowest inlet pressure at which the first-stage regulator still holds its outlet setting (10 psig is typical).

—Containers required
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Vaporization of the containers in service versus temperature

Vaporizing capacity of the containers in service at the design level, compared with the demand.

Tap the chart to see the values.

Vaporization of one container versus liquid level

At the lowest temperature entered. Below the design level, the container no longer meets its share of the demand.

Tap the chart to see the values.

Safety separation distances

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Method, assumptions and references

Equations used

Demand: ṁ = input × diversity ÷ heating value [kg/h = kW × 3.6 ÷ (MJ/kg)]
Vaporization per container: ṁv = Aw · (1.876 + 0.02651 · (Ta − ΔT)) × fr [kg/h; Aw = wetted area in m²; Ta in °C]
fr = 1 (intermittent) or 0.25 (continuous); ΔT = bubble point of the mix at the minimum pressure − bubble point of propane at 10 psig
Wetted area: vertical cylinder π·D·H·level + bottom; horizontal tank D·L·θ + 2 segments, θ = arccos(1 − 2·level)
Containers in service: N = round up(ṁ ÷ ṁv); autonomy = N · capacity · (1 − level ÷ fill) ÷ ṁ

Assumptions and limits

  • The vaporization correlation was fitted to Table 4 of the Emerson/Fisher LP-Gas Serviceman’s Handbook (LP-10): 150 to 1,000 gal ASME tanks, half full, 70% relative humidity, intermittent draw. It reproduces that table within ±13% and the 100-lb cylinder table within ±16%. For continuous draw the handbook multiplies by 0.25.
  • Butane blends: temperature is shifted by the difference between the bubble point of the mix at the minimum pressure and that of propane at 10 psig (Raoult’s law, Clausius–Clapeyron vapor pressures). Container dimensions are approximate; use manufacturer dimensions and your supplier’s vaporization chart when available.
  • No sun, rain, snow or ground contact; frosted containers vaporize less. Separation distances for containers of 125 gal or more follow NFPA 58 Table 6.4.1.1 (aboveground); other rules are not evaluated.

Standards and technical documents

  • Emerson (Fisher Regulators): LP-Gas Serviceman’s Handbook (LP-10), vaporization tables for ASME tanks and DOT cylinders
  • NPGA / Propane Education & Research Council: Propane Exchange and Cylinder Safety training materials
  • GPA Standard 2140 and ASTM D1835: Specifications for liquefied petroleum (LP) gases
  • NIST Chemistry WebBook: vapor pressure of propane and n-butane

U.S. regulations

  • NFPA 58: Liquefied Petroleum Gas Code (container location and separation distances, Table 6.4.1.1; installation of cylinders and tanks)
  • OSHA 29 CFR 1910.110: Storage and handling of liquefied petroleum gases
  • International Fire Code, Chapter 61: LP-gas
  • DOT 49 CFR Parts 178 and 180: cylinder specifications and requalification

Frequently asked questions

How much propane does an appliance burn per hour?

Divide input by heating value: a 400,000 Btu/h appliance burns about 18.6 lb/h (21,548 Btu/lb), or 4.4 gal/h at 91,500 Btu/gal.

How much vapor can a 500 gal tank supply?

Per the LP-10 handbook, a half-full 500 gal tank supplies about 360,000 Btu/h at 20 °F with intermittent draw, and about a quarter of that with continuous draw. At 30% liquid, about 270,000 Btu/h.

Why size at a low liquid level?

Vaporization depends on the tank wall wetted by liquid. Just before a refill, the level is lowest and so is the capacity; the system must still work then.

How far must a propane tank be from a building?

NFPA 58 Table 6.4.1.1 sets 10 ft for aboveground tanks of 125 to 500 gal water capacity and 25 ft from 501 to 2,000 gal, with exceptions. Cylinders under 125 gal have other location rules.