The following is a NASA site that gives the transits of Mercury over seven centuries.
“During May transits, the apparent diameters of the Sun and Mercury are 1902 and 12 arc-seconds, respectively. Thus, Mercury appears to be 1/158 the size of the Sun. In contrast, the apparent diameters of the Sun and Mercury during November transits are 1937 and 10 arc-seconds, respectively. So then Mercury appears to be 1/194 the size of the Sun.”
And, for you Andy, there is a spreadsheet you can download. It gives the start and finish times and also how much you can see at your location.