What is the difference between a GTIN and a SKU?

A GTIN is licensed to your company by GS1 and is unique across every company in the world, which is why a retailer anywhere can scan it and know what the product is. A SKU is a code you invent for your own stock keeping. It means nothing outside your business, two unrelated companies can use the same SKU string, and no retailer will accept one where a GTIN is asked for. Most businesses keep both and map one to the other in their own catalog.

Can you convert an ASIN to a GTIN?

No. There is no formula, because the two numbers were assigned by different parties. Amazon creates an ASIN when a listing page is created, while the GTIN was issued earlier from a GS1 company prefix. Going from one to the other is a lookup against the listing rather than a conversion, and it only works if the listing was created with a GTIN in the first place.

Is a UPC the same as an EAN?

They are the same kind of number at different lengths. A UPC-A is a 12-digit GTIN used in the US and Canada, and an EAN-13 is a 13-digit GTIN used through most of the rest of the world. A UPC becomes an EAN-13 by adding a leading zero and a GTIN-14 by adding two, and the check digit does not change because leading zeros contribute nothing to the weighted sum. An EAN-13 only has a 12-digit form if it starts with a zero.

Do I need to buy UPCs and EANs separately?

No. When you license numbers from GS1 you receive numbers from your company prefix, and whether one is printed as a UPC-A or an EAN-13 is a decision made later. There is no separate registration for one format or the other.

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Guidebeginner7 min read

UPC vs EAN vs GTIN vs SKU vs ASIN: Which Number Is Which

One product ends up carrying four or five different numbers, and only some of them mean anything outside your own business. UPC, EAN and GTIN are three names for the same globally issued number, and converting between them is arithmetic. A SKU is yours, an ASIN is Amazon's, and an MPN is the manufacturer's, so none of the three converts into a GTIN at all. When a form rejects your number, it is almost always because one of those last three was typed into a field expecting one of the first three.

Nobody sets out to collect product identifiers. You pick a SKU so your own spreadsheet makes sense, a marketplace hands you a listing ID, a supplier quotes a part number, and then a retailer asks for "the GTIN" and you have four numbers in front of you and no idea which one they mean.

This page is the map. Not what each acronym expands to, which you can get anywhere, but which numbers are the same thing wearing different names, which ones convert into each other, and what actually breaks when you put the wrong one in a field.

The whole thing in one table

Identifier	What it is	Who issues it	Where it is unique	What it costs
GTIN	The umbrella term for the number under a retail barcode	GS1, via a prefix licensed to your company	Globally, across every company	Paid, licensed to you
UPC	A 12-digit GTIN, the North American format	GS1 (it is a GTIN)	Globally	Same numbers, no separate purchase
EAN	A 13-digit GTIN, the format used almost everywhere else	GS1 (it is a GTIN)	Globally	Same numbers, no separate purchase
SKU	Your own stock-keeping code	You, however you like	Inside your business only	Free
ASIN	Amazon's identifier for a listing page	Amazon, when the listing is created	Inside Amazon only	Free, and not yours to control
MPN	A manufacturer's part number	The manufacturer	Inside that manufacturer's catalog	Free

The dividing line runs between the top three rows and the bottom three. The top three are one number issued by a standards body, which is why any company in the world can look at it and know it means your product. The bottom three are local names, each meaningful only inside the system that invented it.

That is the whole idea, and almost every mistake below is a version of forgetting it.

UPC, EAN and GTIN are the same number

They are not three competing standards. GTIN is the umbrella term, and UPC and EAN are two of the lengths it comes in:

UPC-A is a 12-digit GTIN, the format you see in the US and Canada
EAN-13 is a 13-digit GTIN, the format used through most of the rest of the world
GTIN-14 is the 14-digit form used for cases and cartons, and increasingly as the internal format retailers store everything in

When you license numbers from GS1 you are not buying "UPCs" or "EANs". You get numbers from your company prefix, and the format is a printing decision made later. There is no separate registration for one or the other, and a European retailer will not reject a number because it was printed as a UPC.

For what is actually inside the digits, the prefix, the item reference and the check digit, see what is a GTIN. This page cares about what sits beside it.

What converts, and what only looks like it converts

This is where the searches go wrong. People look for a upc to gtin converter and an asin to gtin converter in the same session, as though the two operations were the same kind of thing. They are not remotely alike.

These are arithmetic. Nothing is looked up, and the answer is always the same:

A 12-digit UPC becomes a 14-digit GTIN by adding two leading zeros. 012345678905 becomes 00012345678905.
The same UPC becomes an EAN-13 by adding one leading zero.
An EAN-13 becomes a UPC-12 by dropping its leading zero, but only if it starts with a zero. If it starts with anything else, there is no 12-digit form of that number, and forcing one produces a different product's identifier.

The check digit does not change when you pad, which surprises people who expect to recalculate it. The padding goes on the front, the zeros contribute nothing to the weighted sum, and the digit that was correct at 12 digits is still correct at 14.

Convert a UPC to a GTIN

Paste a 12-digit UPC to see its 14-digit GTIN form. The check digit at the end does not change, which is the point.

Enter a UPC, EAN, or GTIN

Include the check digit. The full number, exactly as it appears under the barcode.

Try:

Open the full tool

These are not conversions at all. There is no formula, because the two numbers were assigned by different parties for different reasons:

ASIN to GTIN is a lookup, not a conversion. Amazon minted the ASIN when the detail page was created. The GTIN was minted years earlier by whoever holds the GS1 prefix. Nothing in one encodes the other. What you can do is look up the listing and read the GTIN it was created with, assuming it was created with one and the seller filled it in.
SKU to GTIN is not a thing either. Your SKU is a name you chose. If you want a mapping, you build it: a column in your own catalog with the SKU in one side and the GTIN in the other. Every business that sells at retail eventually keeps that table, and keeping it early saves a lot of pain.
MPN to GTIN is the same story, one row further out. The manufacturer chose the part number and GS1 issued the GTIN, and only the manufacturer's own records connect them.

A useful recognition test when you are staring at an unlabelled number: GTINs are all digits, exactly 8, 12, 13 or 14 of them, and pass a check digit test. ASINs usually contain letters. SKUs and MPNs contain anything at all, because nobody constrained them. If it does not validate as a GTIN, it is not one.

The SKU distinction, which matters most in practice

Of everything on this page, this is the one that costs people real money.

A SKU is yours. You invent it, it can say anything, and its whole job is to make your own operation legible: HOT-SAUCE-250ML-6PK is a good SKU precisely because a human in your warehouse can read it. Nothing outside your business has any way to interpret it, and nothing outside your business is expected to.

A GTIN is licensed to you by GS1, and is unique across every company in the world. That is the only reason a retailer can scan a jar at a register in another country and know what it is.

The two are not interchangeable in either direction:

A retailer will not accept a SKU where a GTIN is asked for. Not because it is badly formatted, but because there is nothing behind it. Two unrelated businesses can and do use the same SKU string.
A GTIN makes a poor SKU. It carries no meaning for your team, and you cannot change it later, because it is printed on packaging that is already in the world.

Keep both. The SKU runs your business and the GTIN travels outside it.

ASINs, and why they are not yours

An ASIN identifies a page in Amazon's catalog, not a product in the world. Amazon creates it, Amazon owns it, and it means nothing to any other retailer.

Two consequences worth knowing before you plan around one:

An ASIN is attached to a listing, not to you. If you are matching an existing detail page rather than creating one, you are selling on somebody else's ASIN.
Having an ASIN does not mean you have a GTIN. For most new listings Amazon requires a GTIN and checks it against GS1's records to confirm the prefix is registered to you. Our Amazon guide covers where exemptions apply and what documentation Brand Registry asks for.

What actually breaks when you use the wrong one

Every failure below is a real ordering of events, not a hypothetical:

A SKU typed into the GTIN field. Best case the form rejects it and you lose ten minutes. Worse case is a channel that accepts anything digit-shaped, and the listing goes live carrying a number that belongs to someone else's product.
One GTIN reused across variants. A 250ml and a 500ml bottle sharing a number will scan, and the register will price and count one of them as the other. Every distinct saleable variation needs its own number, which is the rule that makes people undercount how many they need to buy.
An EAN-13 forced into 12 digits. Dropping a leading digit that is not zero does not shorten a number, it changes it. The result usually still passes a casual glance and identifies nothing.
A GTIN that is not registered to you. Nothing about a resold number looks wrong. It scans, it validates, and it fails the day a channel checks the registry rather than the format. Cheap UPC codes is the full version of that story.
An ASIN quoted to a retailer as a product code. It identifies an Amazon page. Outside Amazon there is nothing to look it up in.

Which one do you actually need?

Work outwards from your own business:

A SKU, always. Free, immediate, and the thing your own inventory runs on. You already need this before anyone asks for anything else.
A GTIN, as soon as something outside your business has to scan or verify your product. That is most retail shelves and most marketplaces. Which channels genuinely require one is a longer answer, and do I need a UPC to sell online goes channel by channel.
An ASIN and an MPN, if they apply. Neither is something you go and get. The ASIN arrives with the listing, and the MPN comes from whoever manufactured the thing.

If step 2 applies to you, how to get a UPC code covers both routes GS1 US offers, a single GTIN or a company prefix, along with the current prices and how to size a prefix against your real product range.

One more you will see: ISBN

Books have their own identifier, and it is less separate than it looks. An ISBN-13 is a GTIN-13, which is why a bookshop register scans it like anything else. It begins 978 or 979 and is issued through the ISBN agency for your country rather than through GS1, so publishing is one of the few cases where the number comes from somewhere else and still works everywhere.

The short version

UPC, EAN and GTIN are the same globally licensed number at three lengths, and moving between them is padding. SKU, ASIN and MPN are local names issued by you, by Amazon and by a manufacturer, and none of them converts into a GTIN because nothing connects them but a table somebody keeps.

Once you have the GTIN, it is also the number that carries forward into 2D barcodes: a GS1 Digital Link QR code is the same GTIN in a different carrier, and none of the identifiers on this page have to change for it.