Here’s a handy test. Look at your fingers. The longer your ring finger is compared to your index finger, the more testosterone you were exposed to in the womb. The average ratio for women is 0.991 and 0.982 for men.
Consequently, those with higher testosterone levels (i.e. men) tend to perform better at spatial tasks. While those with lower levels (i.e. women) tend to have better verbal skills (the better to nag you with).
Of course when it comes to measuring masculinity, counting solely on your digits just doesn’t add up. For a true measure we need to examine the brain. Luckily, there’s a simple online quiz over at BBC.co.uk (link) that’ll tell you just how manly (or girly) you are!