How Uranium Is Measured: lb U₃O₈ vs kgU vs tU
60-second answer: Uranium is quoted in three unit systems: pounds of U₃O₈ (lb U₃O₈) in North America, kilograms or tonnes of uranium metal (kgU / tU) in the rest of the world, and kgU as UF₆ once the material is converted. The link between them is a fixed chemistry factor: 1 lb U₃O₈ ≈ 0.848 lb U, so roughly 1 tonne U ≈ 2,600 lb U₃O₈. Once you know that ratio, every conversion is simple arithmetic. If you just want the number, the uranium unit converter does it for you; to see what a pound of yellowcake (U₃O₈) actually is, start there.
The reason this trips people up is that a "pound of uranium" and a "pound of U₃O₈" are not the same thing — and contracts, price quotes, and reactor requirements each pick a different convention. This guide sorts out why, gives you the exact factors, and shows a worked table you can check against.
Why the industry runs on three unit systems
There is no single global unit for uranium because the material changes chemical form as it moves down the fuel chain, and different regions standardized on different conventions decades ago.
- North America quotes lb U₃O₈. The spot and term prices you see in US dollars are dollars per pound of U₃O₈ — triuranium octoxide, the oxide concentrate that comes out of a mill. When a headline says "uranium at $X per pound," it means yellowcake. Track that mechanism live on the spot price page.
- The rest of the world quotes kgU or tU. European utilities, the IAEA, the OECD/NEA Red Book, and most national statistics report uranium as the mass of contained uranium metal — kilograms of uranium (kgU) or tonnes of uranium (tU). This measures the actual uranium content, stripping out the oxygen in the oxide.
- Converted material is quoted as kgU as UF₆. After conversion, uranium becomes uranium hexafluoride gas. Conversion and enrichment services are still priced by the mass of contained uranium — "kgU as UF₆" — because what the buyer cares about is the uranium inside, not the fluorine wrapper.
So the same batch of uranium can legitimately be described three ways depending on where it sits in the fuel cycle and who is doing the accounting.
The one factor that matters: U₃O₈ → U
Everything hinges on the difference between the oxide (U₃O₈) and the metal (U). U₃O₈ is three uranium atoms bound to eight oxygen atoms, so a pound of U₃O₈ is only partly uranium — the rest is oxygen.
Using standard atomic masses (U ≈ 238.03, O ≈ 16.00), the uranium fraction of U₃O₈ works out to:
U₃O₈ → U factor = 0.8480 (a pound of U₃O₈ contains about 0.848 lb of uranium metal)
Run it the other way and U → U₃O₈ = 1.1792 (a pound of uranium equals about 1.179 lb of U₃O₈). These are fixed public chemistry constants, not market prices, so they never change.
From that single ratio, the common conversions fall out:
| Convert | Multiply by | Result |
|---|---|---|
| lb U₃O₈ → lb U | 0.848 | pounds of contained uranium |
| lb U → lb U₃O₈ | 1.179 | pounds of U₃O₈ |
| lb U₃O₈ → kgU | 0.3846 | kilograms of contained uranium |
| kgU → lb U₃O₈ | 2.5998 | pounds of U₃O₈ |
| tU → lb U₃O₈ | ≈ 2,599.8 | pounds of U₃O₈ (≈ 2,600) |
| lb → kg (mass) | 0.4536 | kilograms |
The two you will actually use are 1 tonne U ≈ 2,600 lb U₃O₈ and 1 kgU ≈ 2.6 lb U₃O₈. The kgU figure combines the oxide factor (0.848) with the pound-to-kilogram conversion (0.4536): 0.848 ÷ 0.4536 ≈ 2.6.
A worked conversion table
Here is a reference grid so you can sanity-check any figure. Values are rounded.
| lb U₃O₈ | lb U | kgU | tU |
|---|---|---|---|
| 1 | 0.848 | 0.385 | 0.000385 |
| 100 | 84.8 | 38.5 | 0.0385 |
| 1,000 | 848 | 385 | 0.385 |
| 2,600 | 2,205 | 1,000 | 1.0 |
| 10,000 | 8,480 | 3,846 | 3.846 |
| 100,000 | 84,800 | 38,460 | 38.46 |
Worked example: a resource statement reports 5,000 tU in the ground. Multiply by 2,600 to get roughly 13,000,000 lb U₃O₈ — the number a North American investor would recognize. Going the other way, a 2 million lb U₃O₈ annual production target is about 769 tU (2,000,000 ÷ 2,600).
Watch the UF₆ trap
When you see "kgU as UF₆," the figure is still the mass of contained uranium, not the mass of the UF₆ gas itself. UF₆ is heavier than the uranium inside it (one uranium atom plus six fluorine atoms), so the gross weight of a UF₆ cylinder is larger than its kgU rating. For price and requirements accounting, always work in contained-uranium terms (kgU) — that keeps conversion, enrichment, and mining figures on the same basis.
Where you will hit each unit
- Company disclosures and stock analysis. North American producers report production and resources in lb U₃O₈; you will see this across our uranium stocks screener and projects database.
- Global supply-demand data. International bodies use tU. To compare a Red Book supply figure with a US utility's contracted pounds, convert first — mixing units understates or overstates volumes by nearly 3x.
- Fuel-cost modelling. When you build up a delivered fuel cost from mining, conversion, enrichment, and fabrication, each service is priced on its own unit. Our nuclear fuel cost calculator keeps the bases consistent so the total is apples-to-apples.
Quick rules of thumb
- 1 lb U₃O₈ ≈ 0.848 lb U (the oxide-to-metal factor)
- 1 kgU ≈ 2.6 lb U₃O₈
- 1 tU ≈ 2,600 lb U₃O₈ ≈ 2,205 lb U
- 1 short ton U₃O₈ = 2,000 lb U₃O₈
- "kgU as UF₆" = contained uranium mass, not cylinder weight
Need the exact figure for an odd number? The interactive unit converter on our tools page handles lb U₃O₈, lb U, kgU, and tU in both directions.
Frequently asked questions
How many pounds of U₃O₈ are in a tonne of uranium? About 2,600 lb U₃O₈ per tonne of contained uranium (tU). More precisely it is ~2,599.8, using the 0.848 oxide-to-metal factor and the 0.4536 kg-per-pound conversion.
What is the U₃O₈ to uranium conversion factor? A pound of U₃O₈ contains about 0.848 lb of uranium metal (the U₃O₈ → U factor is 0.8480). Going the other way, 1 lb U equals about 1.179 lb U₃O₈.
How do I convert pounds U₃O₈ to kgU? Multiply pounds of U₃O₈ by 0.3846 to get kgU, or multiply kgU by 2.5998 to get pounds of U₃O₈. So 1,000 lb U₃O₈ ≈ 385 kgU.
Why does North America use lb U₃O₈ while everyone else uses kgU? It is a regional convention. North American miners and the US market standardized on pounds of oxide concentrate, while the IAEA, OECD/NEA, and European utilities report contained uranium metal in kilograms and tonnes. Both describe the same material.
Is "kgU as UF₆" the weight of the UF₆ gas? No. It is the mass of the uranium contained in the UF₆, not the total weight of the UF₆ molecule. Conversion and enrichment are priced on contained-uranium terms to stay consistent with mining and reactor-requirement figures.
This article is for informational purposes only, not investment advice.