Nitrogen gas cylinder pressure, sizes and usable gas volume calculation

How Much Gas Is in a Nitrogen Cylinder? Pressure, Sizes and Real Usable Volume

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Introduction

Nitrogen cylinders are everywhere in industry: purging pipelines, pressure and leak testing, food packaging, laser cutting, laboratories and maintenance shops. Yet many buyers do not know how much nitrogen they actually get in a cylinder, how much of it they can really use, or what each cubic metre costs them.

This guide explains nitrogen cylinder pressure and sizes, shows how to calculate the gas inside, explains why the usable amount is lower than the label suggests, and compares the cost with on-site nitrogen generation.

Nitrogen Cylinder Pressure

In India, industrial nitrogen cylinders are commonly filled to about 150 bar (about 150 kg/cm², or roughly 2,200 psi) (1). Some newer cylinders are rated for higher pressures such as 200 bar; the working pressure is always stamped on the cylinder shoulder. Never fill or use a cylinder above its stamped working pressure.

Process pressure is a different thing. The pressure your application needs (for example, 6–8 bar for purging or packaging, or much higher for laser cutting) is set by the regulator, not by the cylinder. Our guide to nitrogen pressure by application covers this (2).

How to Calculate the Gas in a Nitrogen Cylinder

You need two numbers, both stamped on the cylinder: the water capacity (internal volume in litres) and the filling pressure (bar). Then (1):

Volume of gas (litres) = Water capacity (litres) × Pressure (bar)

For the common 46.7-litre cylinder filled to 150 bar:

46.7 L × 150 bar = 7,005 litres ≈ 7 m³ of nitrogen

That is why one standard nitrogen cylinder is usually quoted as “about 7 m³” (3). The formula treats nitrogen as an ideal gas, which is close enough for nitrogen at normal cylinder pressures.

Gas content at different pressures

Gauge Pressure (bar) 46.7 L Cylinder: Gas (litres) 46.7 L Cylinder: Gas (m³) 10.2 L Cylinder: Gas (litres)
200 9,340 9.3 2,040
150 7,005 7.0 1,530
140 6,538 6.5 1,428
130 6,071 6.1 1,326
120 5,604 5.6 1,224
110 5,137 5.1 1,122
100 4,670 4.7 1,020

Table 1: Nitrogen in a cylinder at different pressures (200 bar applies only to cylinders rated for it)

The gas content falls in direct proportion to the pressure. A cylinder delivered at 130 bar instead of 150 bar holds about 13% less nitrogen for the same price, so check the gauge when cylinders arrive.

The Real Usable Volume

You never get all 7 m³ out of a cylinder. Three things reduce what you actually use:

  1. Residual pressure. Cylinders are returned with some pressure left inside, both because regulators stop delivering steady flow at low pressure and to keep moisture and dirt out. If a 46.7 L cylinder goes back at 10 bar, 467 litres (about 7%) goes back with it: you used 6,538 litres, not 7,005.
  2. Process minimum pressure. If your process needs, say, 20 bar at the regulator outlet, the cylinder becomes “empty” for you well before it reaches zero. Returned at 20 bar, a 46.7 L cylinder leaves 934 litres (about 13%) unused.
  3. Under-filling. As above, a cylinder filled to 130 bar instead of 150 bar is already 13% short before you start.
Cylinder Returned At Nitrogen Used (litres) Nitrogen Returned Unused Real Cost per Nm³ (₹700 per Cylinder)
0 bar (theoretical) 7,005 0% ₹100
10 bar 6,538 7% ₹107
20 bar 6,071 13% ₹115
30 bar 5,604 20% ₹125

Table 2: Usable nitrogen and real cost per Nm³ for a 46.7 L cylinder filled to 150 bar

What Cylinder Nitrogen Really Costs

Cylinder nitrogen in India typically costs ₹70–150 per Nm³, depending on location (3). On top of the gas, you pay for cylinder rent, transport and the people who receive, change and track cylinders. Compare that with on-site PSA nitrogen at ₹1.76–10.56 per Nm³, depending on purity (3)(4).

Worked example: 20 cylinders a day

We ran a typical case through the free Absstem ROI calculator (PSA vs Cylinders): 20 nitrogen cylinders a day of 7 m³, at ₹700 per cylinder, 24 hours a day, 30 days a month, with the process needing 99.9% purity.

PSA vs cylinders calculator inputs
Figure 1: PSA vs Cylinders calculator inputs: nitrogen, 20 cylinders
a day, 7 m³, 99.9% purity, ₹700 per cylinder.
PSA nitrogen generator versus cylinder cost calculator results
Figure 2: Calculator result: cylinders cost ₹100 per m³ and ₹52.8 lakh a year; a PSA nitrogen generator costs about ₹2.70 per m³ and ₹3.8 lakh a year.
Nitrogen Cylinders PSA Nitrogen Generator
Nitrogen per day 20 × 7 = 140 m³ 140 m³ (about 5.8 m³/hr)
Cost per m³ ₹700 ÷ 7 = ₹100 About ₹2.70
Total cost per year (calculator) ₹52,80,000 ₹3,81,624

Table 3: 20 cylinders a day – cylinders vs PSA nitrogen generator (Absstem ROI calculator; cylinder cost includes operator and rental)

In this example, a small on-site generator saves about ₹49 lakh a year, before counting the unused gas returned in every cylinder. Run your own numbers in your proprietary Absstem ROI Savings calculator here.

Purity: Paying for More Than You Need

Cylinder nitrogen is usually supplied at a very high purity, typically 99.999% or more (3). Many applications, such as purging, blanketing, food packaging and pressure testing, need far less. An on-site PSA generator lets you choose the purity your process needs, and lower purity means a lower cost per Nm³. See our guide to nitrogen purity grades (5).

When Cylinders Still Make Sense

  • Very low or occasional use, such as a few cylinders a month
  • Portable work at different sites
  • Backup supply for an on-site generator

For anything more than occasional use, an on-site PSA nitrogen generator usually pays for itself quickly, with no deliveries, no empty cylinders to return and no gas sent back unused.

Safety Reminders

  • Store cylinders upright and chained; keep valve caps on during transport.
  • Always use a pressure regulator rated for the cylinder pressure.
  • Use nitrogen only in well-ventilated areas: nitrogen displaces oxygen and can cause asphyxiation without warning.
  • Check the hydrostatic test date stamped on the cylinder before use.

Internal Resources – Next Steps

If you have completed your PESO research and are now ready to evaluate PSA oxygen plant options for your filling station:

Consult Us

For high-purity oxygen generation systems contact us:

References

  1. Absstem Technologies. (2024). Calculation of Volume of Gas Stored in a High-Pressure Cylinder
  2. Absstem Technologies. (2025). Nitrogen Pressure Required for Different Industrial Applications
  3. Absstem Technologies. (2025). Comparison of the Cost of Nitrogen Gas from Different Sources
  4. Absstem Technologies. (2024). Understanding Nitrogen Purity in PSA Nitrogen Generators
  5. Absstem Technologies. (2026). Nitrogen Purity Grades Explained: N2.0 to N6.0 and What Each Is Used For

Frequently Asked Questions

What is the pressure in a nitrogen cylinder?

A full industrial nitrogen cylinder in India is usually filled to about 150 bar (around 150 kg/cm² or 2,200 psi). Some cylinders are rated for higher pressures; check the stamp on the cylinder.

How much nitrogen is in a cylinder?

A standard 46.7-litre cylinder at 150 bar holds about 7,000 litres, or about 7 m³, of nitrogen.

How do I calculate the gas in a cylinder?

Multiply the water capacity in litres by the pressure in bar. For example, 46.7 × 150 = 7,005 litres.

How much of the nitrogen in a cylinder can I actually use?

Usually 85–95%, depending on the pressure at which you return the cylinder. Returned at 10 bar, about 7% of the gas goes back unused.

Is a nitrogen generator cheaper than cylinders?

For regular use, yes. Cylinder nitrogen typically costs ₹70–150 per Nm³; PSA nitrogen costs ₹1.76–10.56 per Nm³ depending on purity.

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