See our size guide for Chest, Body length and Sleeve length. These are for general guidance only but do, coincidentally, conform to M&S sizes for a regular height individual.
The blazer is cut 2/3" (two third inches) larger than actual chest size and this is done for comfort and movement so be sure to order your actual chest size measured with a tape measure under your arms and snugly around your chest and with only a shirt on.
However, upon receipt, if your blazer does not fit to your satisfaction it can be exchanged for another size provided it is returned in an unused condition and in its original packaging. Please check our Returns Policy for more details.