Highly Enriched Uranium
Uranium enriched above 20% U-235; the fissile material for nuclear weapons.
Last refreshed: 12 April 2026
How close is Iran's uranium to weapons grade?
- How much enriched uranium does Iran have?
- 440.9 kg at 60% as of September 2025, the last IAEA verified figure. Current stockpile is unknown.Source: IAEA GOV/2025 report
- How close is 60% enrichment to a nuclear weapon?
- At 60%, the bulk of the separative work is done. Further enrichment to 90% is technically straightforward but would take weeks to months depending on centrifuge capacity.Source: Arms Control Association
- What is a significant quantity of uranium?
- The IAEA defines 25 kg of 90%-enriched uranium as the approximate minimum for a single nuclear device.Source: IAEA safeguards glossary
Background
Highly Enriched Uranium is uranium enriched to 20% or more of the fissile isotope U-235. Weapons-Grade Uranium is typically enriched above 90%. The IAEA considers 25 kg of 90%-enriched uranium the approximate minimum for a single nuclear device, a threshold known as a significant quantity.
Iran's last verified HEU stockpile, recorded by the IAEA in September 2025, was 440.9 kg enriched to 60%. At 60% enrichment, further processing to weapons-grade is technically straightforward: the bulk of the separative work has already been done. Iran's Foreign Minister Abbas Araghchi offered in March 2026 to downblend this stockpile to lower percentages, but the US demanded full removal from the country.
The enrichment gap between Iran's position (right to enrich) and the US position (zero enrichment) was one of three structural deadlocks that collapsed the Islamabad talks in April 2026. Since the Majlis voted 221-0 to suspend all IAEA cooperation on 3 April, no independent verification of the stockpile has been possible.
