By my rough calculations a drop of six to seven points for VTI will put us in a bear market. A bear market is generally defined as a drop of 20% or more from a high. VTI closed above $94 last Friday and the high for this year is a little over $110. If VTI declines to $88 or lower we are technically in a bear market.
Other definitions may use the S&P 500 as the standard, but my preference is to go with VTI as it covers a broader range of U.S. Equity stocks.