How many veterans are there? Memorial Day data

The short answer is there are about 21 million American Veterans as of 2012. As a total, that's about 6.8% of the US population.

For comparison, that's about...

1. The same size as the combined New York City metropolitain statistical area spanning New York, New Jersey, and Connecticut.
2. The entire population of Australia, 22,780,085.

The longer answer is that the US Department of Veterans Affairs has a model called The Veteran Population Model (VetPop2007), which forecasts the Veteran population out to 2035. The VA's data source is here: http://www.va.gov/vetdata/Veteran_Population.asp and this PDF report also attached to this post, which has a couple of other interesting projections, such as the increasing percentage of female veterans.  While the data hasn't been updated recently, and the methodology looks about 5 years old, they have a great interactive map where you can search state-by-state.

I'm actually a little surprised that the total number of veterans is decreasing and projected to keep declining. While this makes sense because the troop deployments in WWII and Vietnam were much larger than recent wars, it still surprises me that the major increases in US population since then don't overwhelm that.  The US population in 1945 was around 140 million, compared to 311 million now.