How do I convert psi to bar for an airbrush compressor?

Divide the psi figure by 14.5038 to get bar, or multiply it by 0.0689476 — the same thing. 20 psi is 1.379 bar. Going the other way, multiply bar by 14.5038: 2 bar is 29.01 psi. kPa is easier to remember: 1 psi is 6.8948 kPa, and 100 kPa is 1 bar. This site's authored reference bands run from 10 to 30 psi, which converts to about 0.69 to 2.07 bar or 69 to 207 kPa. Those bands are editorial starting comparisons, not a required range for every brush, paint or job.

What is 0.3 mm in inches for an airbrush nozzle?

0.3 mm is 0.0118 inches, and most people say 12 thousandths when they quote it that way. The usual metric sizes convert like this: 0.15 mm is 0.0059 in, 0.2 mm is 0.0079 in, 0.35 mm is 0.0138 in, 0.4 mm is 0.0157 in and 0.5 mm is 0.0197 in. A converted size is not a compatibility check: replacement nozzles and needles must be the exact matched parts listed for your airbrush model, not the nearest nominal diameter.

Is a US fluid ounce the same as a UK fluid ounce?

No. A US fluid ounce is 29.5735 ml and an imperial (UK) fluid ounce is 28.4131 ml, so the UK ounce is about 4% smaller. On a 9 ml cup the difference is well under half a millilitre, which does not matter; on a 60 ml bottle it is about 2 ml, which does. The thinning ratio calculator on this site uses US fluid ounces, and this converter shows both so the number you read off a bottle matches the bottle.

How many psi is 1 bar?

1 bar is 14.5038 psi, and 1 bar is 100 kPa. That puts the pressure ranges this site writes in psi into context: fine detail work at 10-15 psi is 0.69-1.03 bar, general coverage at 15-20 psi is 1.03-1.38 bar, and primer at 20-30 psi is 1.38-2.07 bar. If your regulator reads to 4 bar or more, most of the useful airbrush range is in the bottom third of the dial.

Why does my compressor gauge not match the converter?

Because a conversion is exact and a gauge is not. Cheap regulators are often accurate to only a few psi and are marked in coarse steps, and the reading changes with air flowing: it sits high with the trigger closed and drops while you spray. Use the converted figure to find the mark, then set the pressure with the trigger open and the air flowing, and trust the spray on scrap over the dial.

Pressure, size and volume tool

Airbrush Unit Converter

The psi to bar conversion an airbrush regulator asks for, millimetres to inches for a nozzle and needle, and millilitres to fluid ounces for what is in the cup — in one place, with the site's authored reference bands printed underneath so you can see where a reading sits. Every conversion is arithmetic done in your browser, from definitions reviewed in October 2026. The bands are editorial comparisons, not measurements or ratings of your equipment, and a converted size is not a fit or compatibility check.

What are you converting?

Pick the unit you have and type the number. Leave a row empty if it is not part of what you are doing — each row converts on its own. All of it happens in this browser tab, so the numbers you type never leave your device.

Pressure — psi, bar or kPa

The figure on your regulator or in the manual. 20 psi, 1.379 bar and 137.9 kPa are the same pressure — type whichever one you have.

Nozzle and needle size — mm or inches

The number stamped on the nozzle cap or listed in the manual for the nozzle and needle set. Handles 0.15 mm up to 50 mm, which covers every airbrush part and catches a mistyped figure.

Paint, thinner or cup volume — ml or fl oz

What is in the cup, the syringe or the bottle. Millilitres and cc are the same thing. US and UK fluid ounces differ by about 4%, so both are listed.

Your conversions

Type a pressure, a nozzle size or a volume — or all three — and choose the unit you have it in. You get every matching unit back, the exact factor used for each conversion, and a short reading of whether the figure is in the range airbrushing normally works in.

How the airbrush unit converter works

Each row is its own conversion, so you can use one and ignore the rest. The arithmetic behind them is exact and short enough to check by hand.

Pressure. Everything is converted through psi, the unit this site writes pressure in: 1 bar is 14.5038 psi and 1 psi is 6.8948 kPa, so 20 psi comes back as 1.379 bar and 137.9 kPa.
Nozzle and needle size. Inches and millimetres are linked by an exact definition — 1 inch is 25.4 mm — so 0.3 mm is 0.0118 in and 0.5 mm is 0.0197 in.
Volume. Millilitres are the working unit: 1 US fluid ounce is 29.5735 ml and 1 UK fluid ounce is 28.4131 ml, which is why a bottle can read 2 fl oz on one label and 60 ml on another.
The reading underneath. Each result also says where the figure sits against the pressure, nozzle and cup ranges this site already quotes, so you can tell a normal bench number from a mistyped one.

Nothing is looked up while you use it. There is no compressor database behind the page, no gauge model to pick and no account to create — only the definitions above applied to your number.

Reference: what the numbers usually look like

Short tables of the figures this site quotes, in both sets of units, so the number on your gauge or your nozzle cap has somewhere to sit. They are general hobby ranges for scale-model work, reviewed on2026-10-14, not measurements of your equipment.

Working pressure by job

Job on the bench	psi	bar	kPa
Fine detail lines and freehand camouflage	10-15 psi	0.689-1.034 bar	68.9-103.4 kPa
Miniature figures (28-54 mm)	10-18 psi	0.689-1.241 bar	68.9-124.1 kPa
General coverage and single-colour coats	15-20 psi	1.034-1.379 bar	103.4-137.9 kPa
Primer and base coats	20-30 psi	1.379-2.068 bar	137.9-206.8 kPa

These job bands are the same authored ranges the Airbrush PSI and Needle Size Selector uses. The 30 psi top of the primer band is this site's general-airbrushing rule of thumb, not a rating of any compressor.

Nozzle and needle sizes

Metric	Imperial	What it is for
0.15 mm	0.0059 in	Narrow nominal sets, often used for line work and small detail.
0.2 mm	0.0079 in	A common detail set on gravity-feed airbrushes.
0.3 mm	0.0118 in	A common nominal all-round size in this site's comparison table.
0.35 mm	0.0138 in	Slightly broader than 0.3 mm, still controllable for detail.
0.4 mm	0.0157 in	Coverage work, base coats and general spraying.
0.5 mm	0.0197 in	Primer, clear coats and large areas.

Numeric markings are not a universal fit rule. A nozzle and needle must be the exact matched parts the maker lists for your airbrush model; a nearby number, matching look or converted diameter does not establish that two parts fit. Check the model's parts list or manual before ordering.

Cup and bottle volumes

Metric	US fluid ounces	UK fluid ounces	What it is
1 ml	0.034 US fl oz	0.035 UK fl oz	A syringe's worth: about 20 drops of a water-thin liquid.
3 ml	0.101 US fl oz	0.106 UK fl oz	A detail cup, the size the thinning examples on this site use.
5 ml	0.169 US fl oz	0.176 UK fl oz	A small gravity-feed cup.
9 ml	0.304 US fl oz	0.317 UK fl oz	A common gravity-feed cup marking.
15 ml	0.507 US fl oz	0.528 UK fl oz	A large gravity-feed cup, or a small mixing bottle.
30 ml	1.014 US fl oz	1.056 UK fl oz	A mixing bottle or a small thinner bottle.
60 ml	2.029 US fl oz	2.112 UK fl oz	A thinner, cleaner or varnish bottle.

Where these figures come from

The conversions are definitions, not opinions: 1 inch is 25.4 mm by definition, 1 US fluid ounce is 29.5735 ml, 1 UK fluid ounce is 28.4131 ml, and 1 psi is 0.0689476 bar or 6.894757 kPa. Anyone running the same multiplication gets the same answer.

The reference bands are the site's own authored working ranges, not measurements of your equipment. The job bands come from the same pressure figures the Airbrush PSI and Needle Size Selector uses, and the selector's 8-35 psi display window is what the reading underneath your result refers to. That window is a tool boundary, not an atomisation or safety limit for every airbrush. The nozzle and needle sizes are the nominal sizes the site's needle-size guidance covers; they are not a universal standard or a compatibility check. Cup and bottle volumes are the markings a modeller meets rather than a standard.

Where this page and a manual disagree, the manual wins. A gauge marked in bar by the manufacturer is the authority on what its own needle position means.

What this converter does not do

It does not tell you what pressure, nozzle or ratio to use. It converts the number you already have — the selector, the compressor calculator and the thinning calculator are the tools that suggest figures.
It cannot know how accurate your gauge, cup, syringe or dropper is. A conversion is exact; a reading off a dial is not.
It carries no brand data — nothing about a particular airbrush model's nozzle markings, needle taper or air cap — and it does not check part compatibility. Use the exact matched nozzle and needle listed for your model.
It converts bar, kPa, psi, mm, inches, millilitres and fluid ounces only. No horsepower, no air delivery in litres per minute, and no correction for altitude, temperature or humidity.
Even a correct conversion cannot establish part compatibility, a safe working pressure for your equipment, a compressor's duty cycle or its airflow under load. Those come from the maker's model-specific documentation, your regulator and a test.
It does not save or send anything. Close the tab and the numbers are gone, because they were never written down anywhere but the screen.

Airbrush unit questions

How do I convert psi to bar for an airbrush compressor?: Divide the psi figure by 14.5038 to get bar, or multiply it by 0.0689476 — the same thing. 20 psi is 1.379 bar. Going the other way, multiply bar by 14.5038: 2 bar is 29.01 psi. kPa is easier to remember: 1 psi is 6.8948 kPa, and 100 kPa is 1 bar. This site's authored reference bands run from 10 to 30 psi, which converts to about 0.69 to 2.07 bar or 69 to 207 kPa. Those bands are editorial starting comparisons, not a required range for every brush, paint or job.
What is 0.3 mm in inches for an airbrush nozzle?: 0.3 mm is 0.0118 inches, and most people say 12 thousandths when they quote it that way. The usual metric sizes convert like this: 0.15 mm is 0.0059 in, 0.2 mm is 0.0079 in, 0.35 mm is 0.0138 in, 0.4 mm is 0.0157 in and 0.5 mm is 0.0197 in. A converted size is not a compatibility check: replacement nozzles and needles must be the exact matched parts listed for your airbrush model, not the nearest nominal diameter.
Is a US fluid ounce the same as a UK fluid ounce?: No. A US fluid ounce is 29.5735 ml and an imperial (UK) fluid ounce is 28.4131 ml, so the UK ounce is about 4% smaller. On a 9 ml cup the difference is well under half a millilitre, which does not matter; on a 60 ml bottle it is about 2 ml, which does. The thinning ratio calculator on this site uses US fluid ounces, and this converter shows both so the number you read off a bottle matches the bottle.
How many psi is 1 bar?: 1 bar is 14.5038 psi, and 1 bar is 100 kPa. That puts the pressure ranges this site writes in psi into context: fine detail work at 10-15 psi is 0.69-1.03 bar, general coverage at 15-20 psi is 1.03-1.38 bar, and primer at 20-30 psi is 1.38-2.07 bar. If your regulator reads to 4 bar or more, most of the useful airbrush range is in the bottom third of the dial.
Why does my compressor gauge not match the converter?: Because a conversion is exact and a gauge is not. Cheap regulators are often accurate to only a few psi and are marked in coarse steps, and the reading changes with air flowing: it sits high with the trigger closed and drops while you spray. Use the converted figure to find the mark, then set the pressure with the trigger open and the air flowing, and trust the spray on scrap over the dial.

Next steps

A converted number is only useful once it is set on something. These are the tools and guides that turn a figure into a pass on the model.