Former Harvard physics prof Andrew Foland has a blog called Nuclear Mangos, which he describes both it and its amusing names as follows:
This blog is intended to provide reliable technical analysis of nuclear issues with non-state actors and nuclear beginner states. Some technical issues have important policy implications that citizens in a democracy should be able to make informed decisions about. The motivation for the blog has been the incredible amount of lies & hyperbole on the Iran situation of early 2006. The blog title is to remind you constantly of the quality of minds in charge of our nuclear security today.
(Being one of my favourite fruits, I find the blog’s title insulting to mangoes!)
After reading comments to a Salon article on Andrew Ledeen’s new book, The Iranian Time Bomb: The Mullah Zealots’ Quest for Destruction (also covered in a recent article in National Review), Foland put together a comparative bar chart, shown below, that sizes up the U.S. and Iran on various metrics that one might use in a threat assessment:

Based on the CIA World Factbook’s data for the U.S. and Iran, as well as Uranium Enrichment and Nuclear Weapon Proliferation and Iranian Centrifuge Developments.
Click the graph to see the original at full size.
SWU, measured in the rightmost bars, is short for Separative Work Units, a unit of measurement used in the nuclear power industry. According to the USEC site:
A SWU is a unit of measurement of the effort needed to separate the U-235 and U-238 atoms in natural uranium in order to create a final product that is richer in U-235 atoms.
Most naturally-occurring uranium is too low in uranium-235 to be used in nuclear reactors; it needs to be “enriched” first. The SWU measure for Iran — that is, the work being done to enrich uranium so that it’s usable for creating nuclear reactions, whether for making electricity or for making the “Great Satan” cry — is too low to show up in the chart; Foland writes that its value is 0.00015.
Based on these numbers, Iran just isn’t anywhere near America’s weight class. As Foland puts it:
By international standards, Iran is a poor, underdeveloped country with substantial infrastructural lacks. If such a country is indeed an existential threat to ours, it can only be the result of some mighty serious mismanagement of American power.
These numbers don’t change the fact that the Iranian government comprises some of the worst examples of humanity, but it does challenge the neocon notion that a military solution — and soon — is necessary.