Start with your height
As a general MTB reference: S for 5'1"–5'6", M for 5'6"–5'10", L for 5'10"–6'2" and XL above 6'2". Every brand publishes its own chart; always treat it as the final word.
Check standover
Standing over the bike with both feet flat, you should have clearance between you and the top tube.
Between sizes?
Go smaller for agility, larger for stability on descents and long rides.
Fine-tune the rest
Saddle height, stem length and bar width complete your fit. Message us and we will help you choose.