Pressure Gauge Range Selection Guide: How to Choose the Right Range

To choose a pressure gauge range, take your normal operating pressure and divide it by 0.75 for a steady load, or by about 0.66 for a pulsating load, then pick the next standard range above that figure. A line that runs steadily at 8 bar suits a 0 to 16 bar gauge, and a line that pulses up to 7 bar suits a 0 to 16 bar gauge as well. Getting this right protects the gauge from overpressure, keeps readings accurate and gives the pointer room to work in the most readable part of the dial. This guide shows the full method with a selection chart, unit conversions and worked examples.

Why the range matters

A gauge range does three jobs at once. It sets how much overpressure the gauge can tolerate, it determines how finely you can read the dial, and it sets the size of the permitted error. Accuracy on an analogue gauge is stated as a percentage of full scale, so a 0 to 100 bar gauge with 1.0% accuracy can be wrong by 1 bar anywhere on the scale. If you use that gauge on a line that normally runs at 5 bar, the 1 bar error is 20% of what you are trying to read.

Too small a range is a different problem. A gauge that runs near or above its full scale is stressed continuously. The Bourdon tube takes a permanent set, the pointer stops returning to zero and the gauge reads low. That is dangerous on a system where a low reading hides a real overpressure.

The rule of thumb for steady and fluctuating pressure

Selection guidance in EN 837-2, the companion to the gauge standard EN 837-1, recommends limiting how much of the scale you use in normal service:

• Steady pressure: keep the working pressure to about three quarters (75%) of full scale or less.
• Fluctuating or pulsating pressure: keep the maximum to roughly two thirds of full scale or less.
• Short-term peaks: a gauge can usually see full scale briefly, but not as a regular working value.

Treat these as starting points and always check the datasheet of the gauge you plan to use. Some of our gauges state their own overpressure protection. The AD-D-2 stainless steel gauge, for example, lists protection of 125% of full scale up to 10,000 kPa, with lower percentages for higher ranges.

Standard ranges

Gauges are not made in every possible range. Metric gauges follow a series of preferred values, repeated in decades. In bar, the common series is 0.6, 1, 1.6, 2.5, 4, 6, 10, 16, 25, 40, 60, 100, 160, 250, 400, 600 and 1,000. Each step is roughly 1.6 times the one before, which keeps the choices manageable while giving a sensible fit for most applications. Gauges that use kPa follow a similar pattern, as in the L63 and L100 ranges that run from -100/0 kPa up to 0/4,000 kPa.

Selection chart: from working pressure to gauge range

The percentage in brackets shows how much of the scale your working pressure occupies. Work out your own numbers with the same method: divide the working pressure by 0.75 (steady) or 0.66 (pulsating), then round up to the next standard range.

Worked examples

Example 1: workshop compressed air at 8 bar

The line is steady, so 8 divided by 0.75 gives about 10.7 bar. The next standard range above that is 0 to 16 bar. The working pressure sits at 50% of the scale, which is a comfortable position for reading.

Example 2: hydraulic pump with pulsation at 210 bar

The pressure pulses with every pump stroke, so divide 210 by 0.66, which gives about 318 bar. The next standard range is 0 to 400 bar, and the working pressure occupies about 53%. A liquid filled gauge or a snubber will help damp the pulsation. Read more in our guide to liquid filled vs dry pressure gauges.

Example 3: low pressure air at 30 kPa

For very low pressure gas and air, a standard Bourdon gauge is not sensitive enough. A capsule gauge is a better fit. Our KPCh low pressure gauge reads from 0 to 2.5 kPa up to 0 to 60 kPa, so a 0 to 60 kPa range would suit a 30 kPa working pressure. The KPCh is for air and gas only, and it is not suitable for liquids.

Gauge pressure, absolute pressure and vacuum

Most pressure gauges read gauge pressure. That means zero is atmospheric pressure, and the gauge shows how much the process is above it. Absolute pressure is measured from a perfect vacuum, so atmospheric pressure at sea level reads about 101.3 kPa absolute.

If your system can fall below atmospheric pressure, choose a range that includes vacuum:

• Vacuum range: reads from 0 down to -100 kPa (roughly -1 bar).
• Compound range: reads both vacuum and positive pressure, for example -100 to 0 kPa on a gauge that also covers positive values, or -1 to 2 bar on the PDK PDR100 digital gauge.

Pumps with suction lines, filters and condensers are typical places where a compound gauge is useful.

Unit conversions you will need

Many analogue gauges carry a dual scale to save you the arithmetic. The L63, L100 and the stainless steel AD-D-2, AL-F-2 and AL-H-2 gauges all show kPa in black and psi in red on a white dial. Digital gauges go a step further. The PDK range lets you switch between units such as bar, MPa, psi and kPa at the push of a button.

Other things that affect the right range

Accuracy at the low end

Because accuracy is a percentage of full scale, the relative error grows as the reading falls. If you must read both low and high values on the same line, consider two gauges, or a digital gauge with a finer resolution.

Overpressure and surges

Water hammer, pump start-up and valve closure can send short spikes well above working pressure. If these happen, choose a higher range or a gauge with better overpressure protection, such as a solid front design with blowout protection. The Solfrunt 1981 offers full rear blowout protection and an optional high point indicator to show the highest pressure reached.

Temperature

Our datasheets give a working temperature of up to 60 degrees Celsius and recommend a pigtail siphon for hotter media, such as steam. Temperature changes can also shift the reading, so follow the manufacturer’s guidance.

Test pressure

If the system is hydrostatically tested at a higher pressure than normal, either isolate the gauge during the test or choose a range that covers it. Never expose a gauge to more than its stated limits.

Digital gauges and range selection

The same rules apply to digital gauges, but you have more flexibility because accuracy is better and resolution is finer. The PDK PDR250 is offered in ranges including 0 to 10, 0 to 20, 0 to 35, 0 to 100, 0 to 200, 0 to 250, 0 to 400 and 0 to 700 bar. Our digital pressure gauge buying guide explains how to pair accuracy and range, and the digital hydraulic pressure gauge guide shows how range choice works on real hydraulic circuits.

Checklist before you order

1. Write down the normal working pressure and the highest likely pressure, including surges.
2. Decide whether the load is steady or pulsating.
3. Divide by 0.75 or 0.66 and round up to the next standard range.
4. Check whether you need vacuum or a compound range.
5. Confirm units, dial size and the connection. See our guide to pressure gauge connection types and thread sizes.
6. Match the wetted material to the media.
7. Plan for calibration. See pressure gauge calibration.

Common range selection mistakes

Four mistakes cause most problems. The first is choosing a range because it matches the pressure exactly, which leaves no headroom and overstresses the tube. The second is choosing a range far too high, which makes the gauge hard to read and magnifies the error. The third is forgetting about spikes from pump start-up or valve closure. The fourth is ignoring vacuum on suction lines. Write down the highest pressure the system could see, not only the normal value, and check it against the overpressure rating on the datasheet before you order.

Frequently asked questions

What happens if I choose a range that is too high?

The gauge will be safe but harder to read, and the absolute error grows. A pointer that sits in the bottom 10% of the dial is hard to interpret accurately.

What happens if the range is too low?

The gauge can be overstressed, lose accuracy and eventually fail. Avoid running a gauge continuously at or above full scale.

Is 0 to 10 bar the same as 0 to 1,000 kPa?

Yes. One bar equals 100 kPa, so 10 bar is 1,000 kPa or 1 MPa.

Do I need a different range for water and for air?

The method is the same. The difference lies in the surge risk, which is much higher on water lines because the liquid cannot be compressed.

Can I use one gauge for several pressures?

Only if all pressures fall within the sensible part of its range. Otherwise, use separate gauges or a digital gauge with the right resolution.

Need help picking a range?

Send us your working pressure, media, temperature and connection through our contact page, or browse the pressure gauges and digital pressure gauges categories.