CME Price Limit Guide

On days like these, it's nice to review the price limits for equities and futures. You can find information on the CME Price limits at this URL:

http://www.cmegroup.com/trading/equity-index/price-limit-guide.html

The limits are (generally) 10%, 20% and 30%. According the the CME, here's how the 10% limit works:

The 10 percent limit is initiated if the lead month futures contract is limit offered. Once this has occurred, the limit is in effect for 10 minutes. This means you cannot trade below the limit, but it doesallow you to trade at or above it. Once the 10 minutes has expired one of two things can happen. If the lead month futures contract is not limit offered after 10 minutes, trading will continue with the 20 percent limit in effect. If the lead month futures contract is limit offered after 10 minutes, trading will halt for two minutes. Once the two minutes has expired, trading will resume with the 20 percent limit in effect.

Under NYSE Rule 80B, the 10 percent price limit is not in effect after 2:30 p.m. ET (1:30 p.m. Chicago time). Therefore, after 1:30 p.m. Chicago time, the 10 percent limit is removed and the 20 percent limit would be in effect. For example, if E-mini S&P 500 futures were down 5 percent at 1:30 p.m. ET, the 10 percent limit

See the CME Equity Index Price Limits FAQ (pdf) for more information.