2009 tax rate schedules are at <a href="http://taxes.about.com/od/2009taxes/qt/2009_tax_rates.htm" rel="nofollow" target="_blank">http://taxes.about.com/od/2009taxes/qt/2009_tax_rates.htm</a> If you don't have offsetting losses, multiply your short-term gain by your tax rate. Also consider state taxes.