What is a UN number? How to look one up, with hazmat examples
A UN number is the four-digit ID for a hazardous material's shipping name, like UN1203 for gasoline. How to find one in the US table, plus common examples.
What is a UN number?
A UN number is the four-digit number that identifies a hazardous material's proper shipping name in transport, such as UN1203 for gasoline. The UNECE defines it as "the four-digit number assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods."
The international list is the Dangerous Goods List, Chapter 3.2 of the UN Model Regulations, the name used in Regulation (EU) 2020/878. The current edition is Rev. 24 (2025). In the US, you read the number from Column 4 of the Hazardous Materials Table in 49 CFR 172.101.
UN, NA and ID numbers
The US table uses three prefixes. Section 172.101(e) explains them:
- UN numbers are "considered appropriate for international transportation as well as domestic transportation."
- NA numbers go with names "not recognized for transportation outside of the United States." The NA9000 series is for US transport only, when international standards don't cover the name, or don't cover the emergency response information.
- ID numbers go with names recognized by the ICAO Technical Instructions for air. "Consumer commodity" (class 9, ID8000) is one.
A UN number identifies a transport entry, not a unique chemical. Read it alongside the entry's hazard class, packing group, labels, packaging and quantity limits. Packing groups (PG) I, II and III mean great, medium or minor danger (172.101(f)). A substance can have different UN numbers depending on concentration, form or mixture.
Where the UN number appears
On US shipping papers, the basic description starts with the ID number, then the proper shipping name and hazard class. The packing group follows where assigned (49 CFR 172.202). The rule's own example is "UN2744, Cyclobutyl chloroformate, 6.1, (8, 3), PG II".
Unless an exception applies, non-bulk packages carry the proper shipping name and number, with its "UN", "NA" or "ID" prefix (172.301). On placards and orange panels, the display rules are in 172.332, with special cases in 172.336.
Look for it in section 14 of a safety data sheet. OSHA lists "(a) UN number" under Transport information in HCS Appendix D, though that section is non-mandatory in the US. The EU SDS format has subsection "14.1. UN number or ID number" under Regulation (EU) 2020/878.
How to look up a UN number
- Find the exact proper shipping name in the Hazardous Materials Table and read Column 4. PHMSA's online CFR tool has an HMT tab you can search, sort and export.
- Check the name is an exact match. A search for "Acetone" also returns "Acetone oils" (UN1091) and "Acetone cyanohydrin, stabilized" (UN1541, class 6.1, PG I). Acetone itself is UN1090. Some entries have no number at all because the material is Forbidden.
- If no specific name fits, apply the table's naming rules and pick the most descriptive entry for the hazard. Do not default to "Flammable liquids, n.o.s." (UN1993).
- Already have a number and need the name or response guide? The Emergency Response Guidebook 2024 has an ID number index (yellow pages), a name index (blue) and the guides (orange).
Take the number from the transport list for your mode. A GHS or CLP supply classification won't give it to you.
Common UN numbers
All rows below come from the US table in 49 CFR 172.101. This is a short set of common numbers, not the full list.
| Material | Number | Class | PG |
|---|---|---|---|
| Gasoline (not more than 10% ethanol; also petrol, motor spirit) | UN1203 | 3 | II |
| Ethanol and gasoline mixture, more than 10% ethanol | UN3475 | 3 | II |
| Diesel fuel (I row) | UN1202 | 3 | III |
| Diesel fuel (D row, US domestic) | NA1993 | 3 | III |
| Flammable liquids, n.o.s. | UN1993 | 3 | I, II or III |
| Environmentally hazardous substance, liquid, n.o.s. | UN3082 | 9 | III |
| Environmentally hazardous substance, solid, n.o.s. | UN3077 | 9 | III |
| Hydrogen peroxide, aqueous solutions, 20% to 40% | UN2014 | 5.1 (subsidiary 8) | II |
| Hydrogen peroxide, aqueous solutions, over 40% to 60% (no passenger or cargo aircraft) | UN2014 | 5.1 (subsidiary 8) | II |
| Carbon dioxide, solid (dry ice) | UN1845 | 9 | none |
| Ethanol or ethyl alcohol, including solutions | UN1170 | 3 | II |
| Sodium hydroxide solution | UN1824 | 8 | II |
| Sulfuric acid, more than 51% acid | UN1830 | 8 | II |
For lithium batteries, the same table gives UN3480 for lithium ion batteries and UN3090 for lithium metal batteries. Batteries contained in or packed with equipment use UN3481 and UN3091.
Diesel has two rows. The "I" row (UN1202) is appropriate for international transport, and you may use it domestically too. The "D" row (NA1993) "may be inappropriate for international transportation", so export diesel goes as UN1202.
Strength changes the hydrogen peroxide number: UN2984 from 8% to under 20%, and UN2015 over 60%, stabilized. Sulfuric acid at 51% or less is UN2796, not UN1830.
UN3082 is a "G" entry, so the technical name goes in parentheses in the basic description.
UK and Europe
Road transport in Europe follows ADR, and ADR 2025 has applied since 1 January 2025. In Great Britain, the Carriage of Dangerous Goods Regulations 2009 (CDG09, as amended) apply, and according to the HSE they "cross-refer almost totally to ADR". The US table includes US-only names and rows, so check the list for your mode (ADR, IMDG or ICAO) before you ship outside the US.
You can ask RegAffairs AI for the UN number of a substance and get an answer that cites the Hazardous Materials Table entry.