To convert propane pressure from PSI to inches of water column (in. w.c.), multiply the PSI value by 27.6799. In practical propane work, I usually round that to 27.7 inches w.c. per PSI. So 1 PSI is about 27.7 inches w.c., 0.5 PSI is about 13.84 inches w.c., and the common propane appliance supply pressure of 11 inches w.c. is only about 0.397 PSI. The conversion itself is simple, but you also need to know where the pressure is being measured because tank pressure, first-stage pressure, and appliance pressure are very different.
Quick answer: PSI × 27.6799 = inches of water column. To go the other direction, inches w.c. × 0.0361273 = PSI. For field estimates, I use 27.7 in. w.c. = 1 PSI.
Propane PSI to Inches of Water Column Conversion Formula
When I convert propane pressure, I start with the standard pressure conversion published by the National Institute of Standards and Technology (NIST). NIST lists 1 PSI as 27.67990 inches of water and 1 inch of water as 0.0361273 PSI. That gives us two formulas that cover nearly every propane pressure conversion you are likely to make.
| Conversion | Formula | Field Shortcut |
|---|---|---|
| PSI to inches w.c. | PSI × 27.6799 | PSI × 27.7 |
| Inches w.c. to PSI | Inches w.c. × 0.0361273 | Inches w.c. ÷ 27.7 |
| 1 PSI | 27.6799 in. w.c. | 27.7 in. w.c. |
| 1 in. w.c. | 0.0361273 PSI | 0.036 PSI |
The exact conversion is useful when I am checking a specification sheet or doing a calculation. For quick troubleshooting in the field, 27.7 is normally accurate enough. I would not use a rounded estimate, however, to override an appliance manufacturer’s required inlet or manifold pressure. The appliance data plate and service instructions always take priority.
Quick Propane PSI to Inches Water Column Chart
If you are working with propane regulators, you will often move between PSI and inches w.c. Instead of doing the math every time, I use a conversion chart like this.
| Pressure (PSI) | Inches Water Column | Approximate Propane Context |
|---|---|---|
| 0.10 PSI | 2.77 in. w.c. | Very low gas pressure |
| 0.25 PSI | 6.92 in. w.c. | Low-pressure range |
| 0.36 PSI | 9.96 in. w.c. | About 10 in. w.c. |
| 0.397 PSI | 10.99 in. w.c. | About 11 in. w.c. |
| 0.50 PSI | 13.84 in. w.c. | About 14 in. w.c. |
| 1 PSI | 27.68 in. w.c. | Higher than typical appliance supply pressure |
| 2 PSI | 55.36 in. w.c. | 2-PSI distribution system pressure |
| 5 PSI | 138.40 in. w.c. | Intermediate pressure |
| 10 PSI | 276.80 in. w.c. | Common first-stage regulator outlet range |
| 15 PSI | 415.20 in. w.c. | High compared with appliance pressure |
| 100 PSI | 2,767.99 in. w.c. | Tank-side pressure magnitude, not appliance pressure |
The biggest thing I want you to notice is how small normal appliance pressure is when expressed in PSI. Eleven inches w.c. sounds substantial, but it is only about 0.4 PSI. That is why a standard tire-pressure gauge is not suitable for checking low-pressure propane appliance supply. You need an instrument designed to resolve low gas pressures, such as an appropriate manometer or digital pressure gauge.
Example: How Do I Convert 0.4 PSI to Inches of Water Column?
Suppose your propane pressure reading is 0.4 PSI and you want to know what that means in inches w.c. I multiply 0.4 by 27.6799.
| Step | Calculation | Result |
|---|---|---|
| Starting pressure | 0.4 PSI | 0.4 PSI |
| Conversion factor | 27.6799 in. w.c. per PSI | 27.6799 |
| Calculation | 0.4 × 27.6799 | 11.07196 in. w.c. |
| Rounded result | 11.07196 | 11.07 in. w.c. |
So a gauge pressure of 0.4 PSI is approximately 11.07 inches w.c. That is very close to the 11-inch-w.c. setting commonly associated with propane second-stage and integral two-stage regulators. If you want a deeper explanation of that number, see my guide on what 11 inches water column means for propane.
Why Propane Pressure Is Often Measured in Inches of Water Column
I get this question a lot because PSI is familiar from tires, compressors, hydraulic equipment, and many other pressure systems. Propane appliances are different. After regulation, the gas pressure supplied to an appliance is low enough that PSI becomes an awkward unit.
For example, it is much easier to discuss a reading of 11 inches w.c. than 0.3974 PSI. Inches of water column gives technicians a larger, easier-to-read number for small pressure changes. A change from 11 inches w.c. to 9 inches w.c. is obvious on a manometer. Expressed in PSI, that same change is only from about 0.397 PSI to about 0.325 PSI.
| Pressure | PSI Equivalent | Why Inches w.c. Is Easier |
|---|---|---|
| 9 in. w.c. | 0.325 PSI | Easy to distinguish as a gas-pressure reading |
| 10 in. w.c. | 0.361 PSI | Simple whole-number reference |
| 11 in. w.c. | 0.397 PSI | Common propane regulator reference |
| 12 in. w.c. | 0.434 PSI | Clearly shows a 1-inch change from 11 |
| 14 in. w.c. | 0.506 PSI | Still only about one-half PSI |
An inch of water column is literally a pressure unit based on the pressure needed to support a one-inch column of water under defined conditions. You do not need to build a one-inch water tube to use the unit; modern digital manometers can display inches w.c. directly.
Where PSI and Inches Water Column Appear in a Propane System
This is where conversion becomes more than a math exercise. I do not treat every propane pressure reading as interchangeable. Different parts of a propane installation operate at very different pressure levels.
The pressure inside a propane container is vapor pressure, and it varies substantially with propane temperature. The regulator then reduces that pressure in stages. Marshall Excelsior’s LP-Gas service handbook explains that a regulator may have to deal with tank pressure ranging roughly from 6 PSIG to 240 PSIG while delivering approximately 11 inches w.c. to operating appliances. The exact operating conditions depend on the system, temperature, load, regulator design, and equipment specifications.
| Location in Propane System | Typical Unit Used | Representative Pressure | Equivalent Inches w.c. |
|---|---|---|---|
| Propane container vapor space | PSIG | Variable; can range widely | Not normally expressed in inches w.c. |
| First-stage regulator outlet | PSIG | Often about 10 PSI | About 276.8 in. w.c. |
| 2-PSI distribution system | PSIG | 2 PSI | About 55.36 in. w.c. |
| Second-stage regulator outlet | Inches w.c. | Often set around 11 in. w.c. | 11 in. w.c. = about 0.397 PSI |
| Appliance inlet/manifold | Inches w.c. | Manufacturer-specific | Check appliance data plate/service manual |
For example, Marshall Excelsior describes second-stage regulators that reduce a first-stage pressure that is normally around 10 PSI down to 11 inches w.c. for domestic installations. Its current regulator catalog also lists models with an 11-inch-w.c. outlet set point and adjustment ranges around that value. That is a useful illustration of why you might see PSI on one side of a propane regulator and inches w.c. on the other.
How Do You Convert 10 PSI Propane Pressure to Inches Water Column?
This is a common conversion because approximately 10 PSI is associated with many first-stage propane regulator systems. The math is straightforward:
| Input | Formula | Converted Pressure |
|---|---|---|
| 10 PSI | 10 × 27.6799 | 276.799 in. w.c. |
| Rounded value | 276.799 ≈ 276.8 | 276.8 in. w.c. |
But I would not interpret that as meaning an appliance should receive 276.8 inches w.c. A 10-PSI first-stage outlet is normally reduced again before standard low-pressure appliances. Converting the number helps you compare units; it does not tell you the correct pressure for the next component.
How Do You Convert 2 PSI to Inches Water Column?
Some propane installations use a 2-PSI distribution system, with additional regulation nearer the appliances. To convert 2 PSI:
| Input | Calculation | Result |
|---|---|---|
| 2 PSI | 2 × 27.6799 | 55.3598 in. w.c. |
| Rounded result | 55.3598 ≈ 55.36 | 55.36 in. w.c. |
Again, that does not make 55 inches w.c. an appropriate appliance manifold pressure. It simply means 2 PSI and approximately 55.36 inches w.c. represent the same pressure.
How Do You Convert Inches of Water Column Back to PSI?
Sometimes you need to work backward. If a regulator, appliance, or manometer gives you a pressure in inches w.c. and you want PSI, multiply by 0.0361273. You can also divide by 27.6799.
| Inches w.c. | Calculation | PSI |
|---|---|---|
| 5 in. w.c. | 5 × 0.0361273 | 0.181 PSI |
| 7 in. w.c. | 7 × 0.0361273 | 0.253 PSI |
| 10 in. w.c. | 10 × 0.0361273 | 0.361 PSI |
| 11 in. w.c. | 11 × 0.0361273 | 0.397 PSI |
| 12 in. w.c. | 12 × 0.0361273 | 0.434 PSI |
| 14 in. w.c. | 14 × 0.0361273 | 0.506 PSI |
| 27.68 in. w.c. | 27.68 × 0.0361273 | About 1 PSI |
Why 11 Inches Water Column Is So Common in Propane
Eleven inches w.c. appears repeatedly in propane literature because it is a common outlet setting for low-pressure propane regulators. RegO’s regulator coding information identifies 11 inches w.c. as a standard outlet-pressure designation on certain regulator families. Marshall Excelsior likewise lists domestic second-stage and integral two-stage regulators designed to deliver 11 inches w.c.
That does not mean every propane appliance requires exactly 11 inches w.c. at its manifold. There can be an inlet-pressure requirement and a separate manifold or burner pressure. Appliance regulators can reduce pressure further. This is why I always distinguish regulator outlet pressure, appliance inlet pressure, and manifold pressure.
If you are diagnosing a pressure problem, my guide on how to check propane regulator pressure explains the basic measurement process, while my article on propane regulator valve problems covers common regulator-related symptoms.
Static Pressure vs. Flowing Pressure
A conversion formula cannot tell you whether a propane system is operating correctly. Pressure also changes with gas flow. You can have a reasonable pressure reading with every appliance off, then see the pressure fall when a furnace, water heater, generator, or other load starts.
I think of the two readings this way: static pressure tells me what the system is doing with little or no gas flowing, while flowing or load pressure tells me how well the regulator and piping maintain pressure when gas is actually being consumed.
| Reading Type | Condition | What It Can Tell You |
|---|---|---|
| Static pressure | Little or no downstream gas flow | Basic regulator lock-up/resting pressure condition |
| Flowing pressure | One or more appliances operating | Whether pressure is maintained under demand |
| Pressure drop | Compare upstream/downstream or static/load readings | Can help identify undersizing, restrictions, regulator issues, or excessive demand |
This is also why I do not diagnose a propane system from a converted number alone. A reading may convert perfectly from PSI to inches w.c. and still be wrong for the specific operating condition.
Can I Use a Regular PSI Gauge for 11 Inches Water Column?
Usually, a typical general-purpose PSI gauge is a poor choice for low-pressure propane work. Eleven inches w.c. is only about 0.397 PSI. If your gauge has a 0–100 PSI range, 0.4 PSI is less than one-half of one percent of full scale. You will not get the resolution you need to evaluate small changes accurately.
| Instrument Range | 11 in. w.c. as PSI | Practical Usefulness |
|---|---|---|
| 0–100 PSI gauge | 0.397 PSI | Poor resolution for low-pressure gas work |
| 0–15 PSI gauge | 0.397 PSI | Better, but still not ideal for fine appliance checks |
| Low-pressure manometer | Reads directly in in. w.c. | Appropriate when its range and rating match the job |
| Digital gas pressure gauge | May display in. w.c., PSI, mbar, or kPa | Useful when rated and calibrated for the required range |
I recommend using a pressure-measuring instrument intended for gas service and for the pressure range you are testing. Follow the instrument instructions, the appliance manufacturer’s service procedure, and applicable gas-safety rules.
Common Conversion Mistakes I See
Using 28 Instead of 27.6799 Without Knowing It Is an Approximation
For rough field math, 28 inches w.c. per PSI is close. But if I am writing a specification, comparing a test result, or building a table, I prefer 27.6799. At low pressures the difference may be small, but being clear about rounding prevents confusion.
Assuming 11 Inches w.c. Equals 11 PSI
This is a major error. Eleven inches w.c. is only about 0.397 PSI. Eleven PSI would equal roughly 304.48 inches w.c., which is dramatically higher than normal low-pressure appliance supply.
| Value | Correct Equivalent |
|---|---|
| 11 in. w.c. | About 0.397 PSI |
| 11 PSI | About 304.48 in. w.c. |
Confusing Tank Pressure with Appliance Pressure
The pressure inside a propane cylinder or tank is not supposed to be 11 inches w.c. Tank vapor pressure is much higher and changes with temperature. The regulator’s job is to reduce that pressure to a controlled downstream pressure.
Ignoring the Appliance Specification
A conversion tells you equivalent units, not the required setting. If your appliance calls for a specific inlet or manifold pressure, use that requirement. Do not adjust a regulator just because a general propane article says 11 inches w.c. is common.
Adjusting a Regulator Based Only on a Single Reading
Regulators are safety-critical components. If pressure is outside specification, there may be a regulator problem, piping restriction, incorrect sizing, low vaporization capacity, excess load, or another system issue. If you smell propane, suspect a leak, or are not trained to perform gas-pressure tests, stop and have a qualified propane professional inspect the system.
Propane PSI to Inches Water Column Calculator Method
You can do the conversion on any basic calculator. I use this simple sequence:
| What You Know | What You Want | Calculator Entry |
|---|---|---|
| PSI | Inches w.c. | PSI × 27.6799 |
| Inches w.c. | PSI | Inches w.c. ÷ 27.6799 |
| Inches w.c. | PSI | Inches w.c. × 0.0361273 |
For example, if you have 0.35 PSI, enter 0.35 × 27.6799. The answer is about 9.69 inches w.c. If you have 12 inches w.c., enter 12 ÷ 27.6799. The answer is about 0.434 PSI.
Frequently Asked Questions
How many inches of water column are in 1 PSI?
One PSI equals approximately 27.6799 inches of water column. I normally round that to 27.7 inches w.c. for quick calculations.
How much PSI is 11 inches water column?
Eleven inches w.c. equals approximately 0.397 PSI. That is why low-pressure propane systems are normally discussed in inches w.c. instead of PSI.
How much PSI is 14 inches water column?
Fourteen inches w.c. equals approximately 0.506 PSI. Even a 14-inch-w.c. gas pressure is only about one-half PSI.
How many inches water column is 2 PSI propane?
Two PSI equals approximately 55.36 inches w.c. A 2-PSI propane distribution system therefore operates at a much higher pressure than a typical 11-inch-w.c. low-pressure appliance supply.
How many inches water column is 10 PSI propane?
Ten PSI equals approximately 276.8 inches w.c. A first-stage regulator may supply pressure in this range, but that pressure is normally reduced again before reaching standard low-pressure appliances.
Is 11 inches water column the same as propane tank pressure?
No. Eleven inches w.c. is a common regulated downstream pressure. Propane tank vapor pressure is much higher and varies with temperature. Never use an 11-inch-w.c. appliance specification as a target tank pressure.
Should I adjust my propane regulator to exactly 11 inches w.c.?
Not automatically. Some regulators are factory-set around 11 inches w.c., but the correct setting depends on the regulator, system design, appliance requirements, load conditions, and manufacturer’s instructions. I would verify the actual specification before any adjustment.
Bottom Line
When you need to convert propane PSI to inches of water column, multiply PSI by 27.6799. For quick field math, multiplying by 27.7 is usually close enough. Going the other direction, multiply inches w.c. by 0.0361273 or divide by 27.6799.
The math is easy, but the context matters. A value such as 10 PSI may be normal on the intermediate-pressure side of a propane system, while 11 inches w.c.—only about 0.397 PSI—is common on the low-pressure side. Before you decide that a pressure reading is correct or incorrect, identify where you are measuring, whether the system is under load, and what the regulator or appliance manufacturer specifies.
If your reading is unstable, drops sharply when another appliance starts, or falls outside the equipment specification, do not rely on conversion alone to diagnose the problem. Use the correct gas-pressure test procedure or have a qualified propane technician check the system.
Technical Sources
I based the conversion factors and regulator examples in this guide on technical information from the National Institute of Standards and Technology (NIST), RegO, and Marshall Excelsior. Always use the current instructions and specifications for the regulator and appliance you are servicing.
Mike is an experienced propane technician with over 15 years of professional experience in the field. He has dedicated his career to helping customers with their propane needs, from installation to maintenance and repair. Together with Jeremy, he co-founded this website to provide useful information and guidance to customers seeking reliable propane services.
