FYI: According to the X AI
Prior to the June 2025 Israeli and U.S. strikes on Iran's nuclear facilities, the time to further enrich existing 60% enriched uranium (HEU) to weapons-grade levels (typically defined as ~90%+ U-235) would have been very short: days to a couple of weeks for enough material for one or multiple nuclear weapons.
iranwatch.org
This is because enriching natural uranium (~0.7% U-235) to 60% already accomplishes over 90% of the total separative work units (SWU) required to reach weapons-grade. The final step from 60% to 90% requires far less effort. Iran's ~400–440 kg stockpile of 60% enriched uranium (uranium mass; last verified figures around mid-2025, sufficient in theory for roughly 9–11 weapons' worth if further enriched) was stored as uranium hexafluoride (UF6) and could be fed directly into cascades of advanced centrifuges (e.g., IR-6 models at Fordow or Natanz).
armscontrolcenter.org
Expert analyses (using IAEA data on Iran's then-operational capacity of roughly 130 SWU/day across relevant sites, or focused cascades of advanced machines) estimated:Enough 90% HEU for one weapon (~25 kg, per common definitions of a "significant quantity") in as little as 2–7 days (or up to ~1 week), depending on cascade configuration, tails assay (e.g., 20% or 5%), and whether using a subset of IR-6/IR-4 cascades at Fordow.
Enough for 5 weapons in ~1 week or less.
Enough for 8–9+ weapons in up to ~2 weeks (or ~233 kg of 90% HEU in ~3 weeks in some optimized scenarios).