A UN number is a four-digit identifier assigned by the UN Committee of Experts on the Transport of Dangerous Goods to a substance or article that is hazardous in transport. It uniquely identifies the material for regulators, carriers and emergency responders, and is the key into the Dangerous Goods List that supplies the proper shipping name, hazard class, packing group and special provisions.

How do I look up a UN number?

Identify the exact substance, mixture or article (including concentration and physical state), then search the Dangerous Goods List by proper shipping name or by number. Read the full row: class, subsidiary risks, packing group and every special provision. You can use the free DG Inspector UN number lookup tool to pull up any entry quickly, or have it classify directly from a photo of the package and SDS.

Where do UN numbers come from?

UN numbers are assigned by the UN Committee of Experts and published in the UN Recommendations on the Transport of Dangerous Goods — Model Regulations (the 'Orange Book'), updated every two years. Every modal regulation derives from it: IATA DGR for air, the IMDG Code for sea, ADR for European road, RID for rail and 49 CFR for US transport.

What happens if I use the wrong UN number?

Using the wrong UN number is a misdeclaration. It can trigger carrier rejection, shipment delays, and civil penalties — under 49 CFR, hazmat penalties reach tens of thousands of dollars per violation per day. More importantly, the wrong UN number means the wrong packaging, marks and emergency response, which is a genuine safety risk.

Can one substance have more than one UN number?

Yes. Many substances have multiple entries depending on concentration, packing group, physical state or subsidiary risk. Hydrogen peroxide, nitric acid and many solutions each map to several UN numbers. Picking the wrong variant for your concentration is one of the most common classification errors.

UN Number Lookup: How to Classify Dangerous Goods Correctly

To classify a dangerous good, you find its UN number — a four-digit code that is the key to everything else. Identify the exact substance or article, search the Dangerous Goods List by proper shipping name or number, and read the full row it returns: hazard class, subsidiary risks, packing group and special provisions. Get the UN number right and the rest of the regulation almost reads itself. Get it wrong and you have committed a misdeclaration before you have touched the packaging.

This guide walks through the lookup process step by step, shows the traps that produce wrong answers, and points you to a free tool that does the lookup — or the full classification — for you.

What a UN number actually tells you

A UN number on its own is just an identifier (UN1203 is petrol, UN1263 is paint, UN3480 is a lithium-ion battery). Its value is that it indexes a single row of the Dangerous Goods List, and that row supplies:

The proper shipping name (PSN)
The hazard class / division
Any subsidiary risks
The packing group (I, II or III)
The special provisions that modify the rules
The packing instructions, quantity limits and excepted/limited quantity codes per mode

For the full anatomy of the system and what each hazard class covers, read the complete guide to UN numbers and hazard classes.

How to look up a UN number — step by step

Identify the material precisely. Not "acid" but "sulphuric acid, more than 51%." Not "battery" but "lithium-ion, standalone." Concentration, physical state and configuration all change the answer.
Read the Safety Data Sheet, Section 14. The SDS transport section usually states the UN number, PSN, class and packing group. Treat it as a strong hint, not gospel — SDS authors get it wrong, and the figures must still match your actual shipment.
Search the Dangerous Goods List. Look up by proper shipping name (alphabetical) or by UN number (numeric). Watch for multiple entries — concentration bands and "n.o.s." (not otherwise specified) entries are where errors hide.
Read the entire row. Class, subsidiary risks, packing group, and every special provision. Special provisions live in one easily-missed column and routinely change whether something is shippable and how.
Confirm against the package. The UN number marked on the package must match the documents and the actual contents. A mark that contradicts the declared identity is a red flag, not a formality.

The mistakes that cause misdeclarations

Wrong concentration band. Picking the generic entry when a concentration-specific one applies (acids, peroxides).
Wrong chemistry. Calling lithium metal (UN3090) "lithium-ion" (UN3480), or vice versa. See are lithium batteries dangerous goods for the four battery entries.
Ignoring subsidiary risks. A Class 5.1 oxidiser with a subsidiary 8 corrosive risk needs both labels and stricter segregation.
Trusting the SDS blindly. The transport section is a starting point, not a substitute for reading the DGL.
Using an n.o.s. entry without the technical name. Many "not otherwise specified" entries carry Special Provision 274, which requires the technical name in brackets after the PSN.

Look up any UN number in seconds.

Use the free UN number lookup tool to pull up the proper shipping name, hazard class, packing group and special provisions for any entry — then let DG Inspector classify your actual shipment from a photo and the SDS.

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Lookup vs classification — they are not the same

A lookup answers "what does UN1263 require?" once you already know the number. Classification answers the harder upstream question: "given this product in front of me, what is the correct UN number in the first place?" Lookup is a dictionary; classification is the translation. Most costly errors happen at the classification step, before any lookup is even possible — which is why a clean lookup of the wrong number still produces a misdeclaration.

The UN number lookup tool handles the dictionary side instantly. For the translation side — turning a real package and its SDS into the right UN number, packing instruction and document set — DG Inspector reads the evidence and does the classification for you, with the reasoning shown so you can verify it.

Quick reference: high-traffic UN numbers

UN3480 — Lithium-ion batteries (standalone), Class 9
UN3481 — Lithium-ion batteries in/with equipment, Class 9
UN3090 — Lithium metal batteries (standalone), Class 9
UN3091 — Lithium metal batteries in/with equipment, Class 9

The bottom line

Classifying a dangerous good is a disciplined lookup: identify precisely, search the DGL, read the whole row, and confirm against the package. The UN number is the anchor for the proper shipping name, hazard class, packing group and every downstream rule. Once you have the number, the next decision is usually which rulebook applies — IATA, IMDG, 49 CFR or ADR — and from there it is packing, marking and documents.