TL;DR: To check car paint thickness, use a handheld gauge on clean, dry metal panels, take several readings per panel, and compare matching areas across the vehicle. Factory paint on modern UK cars often reads 100–150 µm on steel; isolated readings above 200 µm, or one panel much thicker than its opposite side, warrant closer inspection for filler or a respray.

Checking paint thickness is one of the fastest ways to test whether a used car's bodywork tells a consistent story. Reddit threads from car buyers and detailers repeatedly ask the same practical questions: where should you measure, how many spots matter, and what numbers should make you walk away? This guide answers those questions in plain UK English, without treating any single reading as a verdict on its own.

What you need before you start

You only need three things: a paint thickness gauge, a few minutes per panel, and a simple note-taking habit. A phone notes app is enough. If you are buying rather than polishing, choose a gauge that reads both ferrous (steel) and non-ferrous (aluminium) substrates, because many modern UK cars mix the two.

The Paint Coating Thickness Gauge listed on PaintCoating covers 0–2000 µm (0–78.7 mils), resolves to 0.1 µm, supports Fe and NFe modes, and includes two AAA batteries. Those are the specifications shown on the product page — use them as a reference point, not as a reason to invent numbers for cars you have not measured.

Step 1: Prepare the car and the meter

Park on level ground and ask the seller for access to all major metal panels: bonnet, wings, doors, boot lid and roof if you can reach it safely. Wipe dust off the areas you plan to measure. Wet paint, fresh wax or rainwater can skew how confident you feel about the finish even when the gauge still returns a number.

• Power on the gauge and select the correct substrate mode: Fe for steel, NFe for aluminium.
• Zero or calibrate according to the manufacturer's instructions.
• Decide which panels you will compare before you start — consistency matters more than speed.

Step 2: Choose where to measure

Take readings on flat areas away from edges, badges, swage lines and fuel filler recesses. Those areas often read differently even on untouched factory paint. Good targets include the centre of each door, the middle of the bonnet, the flat section of each front wing, and the boot lid centreline.

Many experienced inspectors compare left and right sides at the same height. If the nearside front door averages 120 µm and the offside front door averages 240 µm, that asymmetry is more meaningful than either number alone.

Step 3: Take multiple readings per panel

Do not trust a single spot. Take at least three to five readings across each panel and note the spread. Hobbyist detailers on Reddit often warn that polishing through paint becomes a real risk when readings are already thin; buyers face the opposite problem — unusually thick readings that may hide filler or a respray.

Write down results in a simple table: panel name, substrate type, reading one, reading two, reading three, and your average. Patterns jump out quickly when you do this on a forecourt.

Step 4: Compare panels instead of chasing one normal number

There is no universal factory figure for every marque and colour. Based on our testing on common UK used cars, untouched steel panels often cluster around 100–150 µm, while aluminium panels can read lower. What matters is whether matching panels on the same car cluster together.

Look for these warning patterns:

• One panel consistently higher than its opposite-side match.
• A very high isolated reading on a single spot, especially above 200 µm on steel.
• Wide spread across one panel while neighbouring panels stay stable.
• Thick readings combined with visual clues such as overspray, mismatched orange peel or fresh-looking bolt heads.

Step 5: Combine gauge readings with a normal used car inspection

A paint thickness check is not a substitute for MOT history, finance checks, a test drive or a professional inspection. It is a fast physical screen that can reveal repairs HPI-style reports never record. Cash-paid parking-lot repairs happen more often than sellers admit in adverts.

Also inspect panel gaps, sealant overspray, replaced clips, colour mismatch in door shuts, and whether the seller becomes evasive when you ask about prior bodywork. If the gauge, the visuals and the paperwork all disagree, trust the physical evidence in front of you.

Common mistakes UK buyers make

• Measuring only the shiniest panel shown by the seller.
• Ignoring aluminium wings and bonnets on newer cars.
• Panicking over one high spot without comparing the opposite panel.
• Skipping readings on replaced crash panels because they are harder to reach.
• Forgetting that plastic bumpers will not give useful metal-substrate readings.

FAQs

Can I check paint thickness without a gauge?

You can look for overspray, inconsistent texture and poor panel gaps, but you cannot objectively compare coating depth. A gauge removes guesswork.

What reading is too high for factory paint?

Context matters. On steel, repeated readings above 200 µm on one panel — especially when the opposite panel reads much lower — is a sensible reason to investigate further.

Will a gauge tell me if filler is present?

It suggests the possibility. Very high readings and inconsistent spreads often align with filler or heavy build coats, but you should confirm with visual inspection and seller questions.

Ready to inspect your next used car?

If you want a portable gauge for forecourt checks, the Paint Coating Thickness Gauge is priced at £84.54 on PaintCoating with free UK delivery. For a deeper overview of what these tools do before you buy, read our used car paint meter buyer's guide.