Checking a car
Thickness gauge readings: what the number on the screen means
The gauge shows 240. Is that a lot or is it normal? Let’s see which values count as factory, where the spread between makes comes from, and why the conclusion comes from comparing panels rather than from the figure itself.
9 min read
There is no single correct number
The commonest question about a thickness gauge is what it should show. The short answer: there is no one figure for every car. Factory coating sits roughly between 60 and 200 µm depending on where and when the car was built, and a “normal” 120 µm on one car already means a repair on another.
What works is not the value but the comparison: symmetrical panels against each other, neighbouring panels against each other, and all of them against the roof. The gauge supplies figures; the conclusion is drawn by a person.
The scale: three bands are enough for a conclusion
The reference points for reading the screen. The boundaries are approximate — this is a frame for comparison, not a standard.
Set your own value
The reading on the gauge screen
120µm
Within the factory range
An ordinary factory coating for most cars. That still does not mean “never painted”: check whether the figure matches the symmetrical panel and the roof.
Factory figures by origin
Average factory values differ noticeably — which is exactly why a single “norm” does not work.
| Origin | Factory coating |
|---|---|
| European | 90–180 µm |
| Japanese | 80–160 µm |
| Korean | 70–140 µm |
| Russian | 60–150 µm |
| Chinese | 90–200 µm |
| American | 90–190 µm |
The table is a guide, not a passport: even at one plant the layer differs from batch to batch, and on a single car the bonnet and the roof can differ by a couple of dozen microns. For something closer, use the reference by make and generation.
Factory thickness reference: 599 entries by make and model →
The main rule: compare panels, not figures
Start with the roof. It is painted least often and sets what factory coating looks like on this particular car. Every other panel is then compared with it and with its own pair: left wing with right, left door with right.
A difference of a few or a few dozen microns is ordinary. A difference of one and a half to two times is a reason to look at the panel more closely and take a few more points on it.
What a micron is and why 1 µm resolution matters
A micron (µm) is a thousandth of a millimetre. A factory coating of 120 µm is 0.12 mm — about a sheet of office paper. The difference between a factory layer and a respray is around a tenth of a millimetre, so a gauge has to resolve single microns rather than tens of them.
Hence the 1 µm resolution: CARSYS gauges show the measured value instead of rounding it to something tidy. A gauge that returns exactly 120 over and over on a real body is more likely adjusting the result than measuring precisely: real measurement always has a small spread — and it is that spread that reveals the edge of a repair.
Colour indication: a verdict without reading numbers
The AVTOPODBOR line has a colour helper: green for factory coating, amber for thickening, red for a likely repair. On a walk-around of fifteen-odd points that saves attention — the result is visible out of the corner of your eye, without looking away from the body.
The numbers do not go anywhere. Colour is a quick pointer; the decision still comes from comparing panels with each other.
When a gauge shows the wrong thing
- Dirt, ice and waterAnything lying on the body adds to the result. Before measuring, the body must be clean and dry, otherwise an inflated figure appears where there is no repair.
- Measuring on an edgeAt the edge of a panel and on a rib the measuring spot runs off the metal and the value drifts. Step back from the edge.
- Tilting the gaugeThe sensor must sit perpendicular to the surface. On a round pillar or a curved panel a spring-loaded probe and continuous mode help — the latter streams readings while the gauge slides across the panel.
- An unfamiliar alloyThe magnetic properties of steel differ from grade to grade. A gauge with automatic metal recognition picks the method itself, but on an unfamiliar alloy it is worth checking against a reference plate.
- PlasticOn bumpers, trim and fibreglass panels there will be no reading at all: there is no metal under the coating to measure down to. That is not a fault but the boundary of the method.
Measurement recommendations: technique and calibration →
Frequently asked
What should a thickness gauge show on a car?
There is no single figure. Factory coating on most cars sits within 80–180 µm, but on Korean and Russian cars it starts at 60 and on Chinese ones reaches 200. What matters is not the number itself but whether symmetrical panels agree.
What paint thickness counts as normal?
What counts as normal is an even coating across the whole body. The absolute value is only a guide: around 80–150 µm for most cars, up to 200 for some manufacturers.
What does 300 µm on a thickness gauge mean?
That is too much for a factory coating: the panel was almost certainly painted again. At that value there is usually no filler under the paint yet — that starts at around 500 µm.
The gauge shows nothing — is it broken?
Most likely you are measuring plastic: there is no metal under a bumper or trim to measure down to. On a metal panel, check that the body is clean and dry and that the sensor is not sitting on an edge.
Why is it 120 µm at one point and 128 right next to it?
That is how it should be: the coating goes on unevenly, and a small spread is the gauge working properly. What should worry you is a difference of several times, not of a few microns.
Knowledge base
Read next
Material that carries the topic on: how to check a body, what the gauge does and which one to choose.
Compare the readings with your own make
A reference of factory thickness by make, model and generation — the figures a reading is checked against.