No, what you are interested in for an intraday hedge is relative intraday movement. Based on last few weeks, ES ADR is about 9.4, and YM is about 90, meaning point-for-point intraday ratio is about 9.6 YM/ES. So, to hedge 15 YM you'll need:
1 ES pt x $50/pt x n ES = 9.6 YM pt x $5/pt x 15...