QR Code Tools New Tool

Free Online QR Code Size Calculator and Colour Contrast Checker

Find out whether your QR code will actually scan before it is printed. Paste what the code holds and the page counts the real modules, checks the colour contrast the way accessibility tools do, works out the module size at your printed width, and tells you the furthest a phone can read it from. Nothing is uploaded.

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Free Online QR Code Size Calculator and Colour Contrast Checker

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What the code holds

The length is what decides how many modules the code needs, and everything else follows from that.

Error correction Higher survives damage, and makes the code bigger.

Quiet zone 4 The empty border, in modules. The specification asks for four.

Colours

Dots #000000

Background #ffffff

A scanner reads brightness, not colour. Dark dots on a light background, always.

Printed size

Width

Measured in

Print resolution

Who is scanning it

Where it will be

Click one to set the size for it.

The width each place needs, worked out backwards from how far away people stand.

The verdict

Paste what the code will hold, and the numbers appear here.

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How to Check Whether a QR Code Will Scan

Four steps, and you find out before it is printed.

Paste what the code will hold

The link, the text, the WiFi string, whatever it is. The length decides how many modules the code needs, and that is where everything else follows from.

Set the colours you want to use

The contrast between the dots and the background is worked out the same way accessibility checkers do it, because a scanner reads brightness rather than colour.

Say how big it will be printed

In millimetres, centimetres or inches, with the print resolution. The page works out how large one module ends up, which is the number that actually decides whether it scans.

Read the verdict and the distance

You get the furthest a phone can read it from, the smallest size that still works, and the pixel dimensions to export at. If something is wrong, it says which number to change.

Key Features & Capabilities

Arithmetic you would otherwise do after the reprint.

Modules counted, not guessed

The real module count comes from building the code, so the version and the capacity are never out of date.

Contrast the proper way

WCAG relative luminance, the same arithmetic accessibility tools use, with a plain pass or fail.

Scan distance

How far away it can be read, and the size you need for a distance you already have in mind.

Print pixels and DPI

The pixel dimensions to export, and whether a module lands on a whole number of pixels.

Quiet zone checked

The empty border is part of the code. Four modules is the specification, and less is a common cause of failure.

It shows you the code

The real thing in your colours at your size, so you can hold your phone up to the screen and test it.

How Far People Stand From a QR Code

The distance is what decides the size, not the design.

Where it is	People stand about	What that means
A business card	15 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A product label	20 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A restaurant menu	30 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A table tent	50 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A flyer or leaflet	30 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A shop window	100 cm away	The code needs to be roughly 10 mm wide or more, by the ten to one rule.
A wall poster	150 cm away	The code needs to be roughly 15 mm wide or more, by the ten to one rule.
A roadside banner	500 cm away	The code needs to be roughly 50 mm wide or more, by the ten to one rule.

Those are starting points. The tool above works out the real figure for your data, because a longer link needs more modules and therefore more width for the same distance.

About QR Code Size and Colour

Most QR codes that fail were not broken when they were made. They were printed too small, or reversed to look better in a brand palette, or placed tight against a border with no quiet zone, and nobody found out until the posters were already on the wall. All three are arithmetic that can be done in advance, which is what this page is for.

The one number everything depends on is the size of a single module, the smallest square in the code. It follows from two things: how many modules the code needs, which depends on how much data and which error correction level, and how wide it will be printed. A phone camera copes with modules down to roughly four tenths of a millimetre, so once you know the module size you know whether the thing will work, and that is a far more useful answer than the overall width.

The module count here is measured rather than looked up. The code is actually built with your data and your error correction level, and the number of modules is read back from it. The alternative is a table of capacities for forty versions across four correction levels, which is several hundred numbers typed by hand, and one wrong entry would make the page confidently wrong. Building the real code cannot drift out of date.

The colour side uses the same relative luminance formula as accessibility contrast checkers, for the same reason: a scanner is looking at how bright one area is compared with another, not at which colours they are. That is why a strong dark blue on a pale yellow is fine and two mid tones that look very different to the eye are not, and why inverting the code, light dots on dark, is the one thing a brand guideline should never ask for.

Frequently Asked Questions

Size, colour, distance and the quiet zone.

It is not the overall size that matters but the size of one module, the smallest square. A phone camera manages down to roughly 0.4mm per module, so a code with 33 modules across plus its quiet zone needs about 16mm. Fewer characters mean fewer modules, which means a smaller code is possible.

If they are dark on light, and the contrast is strong. A scanner reads brightness, not hue, so a dark navy on cream is fine and a mid grey on light grey is not. Light dots on a dark background is the one to avoid: it can look good and a lot of phones will not read it, because nearly every scanner expects the opposite.

A rough but reliable guide: a code can be read from about ten times its own width. A 30mm code works at about 30cm, and a code on a wall people stand two metres from needs to be about 20cm across. It is the mistake people make most often, and the one that costs a reprint.

Not in the way people expect. Higher correction survives damage, dirt and a logo covering the middle, but it also adds data, which means more modules, which means each module is smaller at the same printed size. If the code is already tight, raising the level can make scanning harder rather than easier.

Because the scanner needs plain background to find the edges of the code. The specification asks for four modules of empty space on all sides, and codes placed tight against text, a border or a photograph are a common failure that looks like nothing is wrong.