How is a Tyre Pressure Gauge Calibrated?

If you are a driver or a car owner, then you have probably heard about a tyre pressure gauge or might have had to use one. A tyre pressure gauge is a type of pressure gauge used to measure the pressure of tyres on a vehicle. Car tyres have been designed in such a way that the the pressure within the walls of the tyre can be set to an optimum level, whereby exceeding this value the tyre will be susceptible over-inflation and lead to a higher risk of damage.

Additionally, all tyres- whether used on mega trucks or on small cars- have been rated to carry specific loads at certain pressure hence its always important to know the amount of pressure your tyres are rated to hold when pumped to maximum pressure.

Most Pressure gauges have been calibrated in Kilopascals (kPa). However, there are some you might see calibrated in Pound (force) per square inch (psi) or bars. Check the units of the pressure gauge before you begin calibration. Generally you will find manufacturers will use PSI when referring to pressure measurements.

Importance of calibrating a gauge

Basically, the purpose of calibration is to maintain accuracy of measurement and ensure that your gauge is working well. However, if you fail to calibrate the gauge then you may get errors when using them, which could lead to you driving on an under or over inflated tyre with the associated risks.

One of the common problems that pressure gauges can experience is that the accuracy will drift over time and so there is a reall need for regular re-calibration. As mentioned earlier using the wrong pressure reading of the car tyres means you will likely leave it under-inflated or end up over-inflating it.

Over inflating a car tyre can lead to the bulging of the sidewalls and treads, making a tyre stiff hence reducing the traction and general performance . Additionally, an over inflated tyre will react less to road hazard such as bumps and potholes.

On the other hand, an under-inflated tyre is very flexible hence there will be an excess heat buildup during driving leading to a higher risk of tyre failure and a heavier tread wear.

To reduce the risk of this happening you need to check tyre pressure at least once a month. The cost of calibrating your gauge is insignificant as compared to the cost of having to replace or repair a damaged tyre.

How do you know if your pressure gauge is accurate?

It’s not easy to note that there is an error with your pressure gauge and especially if there is a slight inaccuracies. All gauges have been assigned some calibration interval by the manufacturer and so you must at all times follow the set limits. There are two methods that one may use to check the accuracy of a pressure gauge and rule out the inaccuracies.

The first way, which is more precise, is taking your gauge to a technician where they can test your unit a laboratory environment. Sometimes you can take the gauge to be tested at a local tyre fitters who may have equipment such as a master gauge they use to test gauges. Master gauge is a normal pressure gauge, similar to your pressure gauge, but they have been designed to be always accurate. The two readings will be compared for discrepancies.

The second way is by taking the suspected pressure gauge and measuring a tyre pressure then recording down the readings. Check the same tyre pressure with another gauge and compare both readings. If you get a pressure difference of more than 4 psi, then either one of the pressure gauges is faulty or both gauges are inaccurate. If you get 1 to 2 psi difference in reading then your gauge is accurate.

Steps to re-calibrate

The best way to get your gauge re-calibrated is to send it off to a certified service center or laboratory. They will have specialist equipment to check the calibration before and after re-calibration is completed.

If this is not a option for you then you can try to re-calibrate the gauge at home. We found this following technique discussed on other websites and forums. Before you get too happy its not as easy as you think.

You will need to have the manufacturers instructions on re-calibrating the unit if this method shows that the gauge needs re-calibrating. You will also need the following materials.

  • Water
  • A tape measure of at least 25 metres in length or a length of cable that measures a metre (preferably the tape measure)
  • Flexible pipe such as hose pipe that’s at least 25 metres long.
  • Marker pen
  • An assistant

Once you have gathered all these items and hopefully some to help the next thing you will need to do is find a tall building that you can use to elevate the pipe. The elevation point should be 25 metres above the ground.

1 – Marking intervals on pipe

Unravel the pipe and place it on a flat surface. Place a tape measure beside the pipe and using the marker pen, mark the pipe at a distance interval of one meter i.e. at every one meter point in the tape measure, the markings should correspond the marks on the pipe. If you could not get a tape measure use the 1 metre length of cable to mark the intervals.

2 – Elevate the pipe

Now you have to get to a high elevation point where you can hold the pipe freely. This is where having an assistant will really help. If they can secure the pipe at the elevation point ensuring that the pipe does not touch the ground. At this point you would need to connect the tyre pressure gauge onto the hanging end at ground level.

3 – Check the Accuracy

To make sure your gauge is well calibrated get your assistant to slowly pour water into the flexible pipe. Have them stop pouring once the water reaches the one metre mark, this will be difficult to get right the first time so you will have to give it a few goes before you get it right on the 1 metre mark. With the pipe filled to the one metre mark, an accurate gauge should read 1.4223 psi. If your gauge reads this value, then it does not need re-calibration. To ensure it wasn’t just luck you can also check the gauge readings with the pipe filled with water at 10m, 20m and 25m with respective readings of 14.2, 28.4 and 35.5 psi.

4 – Re-calibration

If you get different reading than 1.4223 psi at one metre mark, then your gauge is inaccurate and needs re-calibration. To do this, re-calibrate your gauge using the manufacturers instructions. To check if the re-calibration has worked your will need to repeat step 2 and 3 till you get the accurate readings. However, if you try the re-calibration several times and the readings fail to match, it will be high time you acquire a new pressure gauge.

As you can probably tell this DIY method of checking your gauge is accurate takes a lot of work and you will need an extra pair of hands to get it done, so its not going to be possible for everyone.

You may decide you can do this type of test using a shorter pipe but you will find that the results you get will not be that accurate.

How often should you calibrate your pressure gauge?

If the gauge is to be installed somewhere, then calibration accuracy should be checked before installation and there after once in a year. If you have your gauge stored in a safe and secure place where it’s not disturbed a lot, then you can do calibration on a regular schedule between three to six months. However, if your gauge falls, then you need to check if accuracy has been altered.

Are cheap tyre gauges accurate?

Price should not be a determining factor since accuracy is the key factor. A gauge may be very expensive but still can be inaccurate.

If you are considering buying a pressure gauge to check tyre pressure then look at the various features available such as accuracy, readability and PSI range. No matter the price go for a gauge that has features that meet your requirements. Most expensive gauges have additional features such as flashlight and thus the choice is yours.


Knowing whether your gauge is accurate and what to do if its not is important. It can help you avoid the expenses incurred during the repair of damaged tyres as a result of it going flat or wearing out due to improper pressure balance.


Calibration – Wikipedia

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