Seems the 'newest' calculation for MHR by age is the Tanaka Formula:

MHR = 208 - (0.7 x age) according to various search engines. (This one happens to be suggested by the Mayo Clinic.)

For women it's MHR = 206 - (0.88 x age);

Active individuals may instead want to use MHR = 211 - (0.64 x age);

DownUnder there's MHR = 206.9 - (0.67 x age);

BIG caveat being formulas can vary by as much as +/- 25 BPM so YMMV.