Here is a math trick:
1. Take your shoe size (if you are a half-size, round up, like if your shoe size is 10 1/2, round up to 11)
2. Multiply it by 5
3. Add 50
4. Multiply by 20
5. Add 1,014
6. Subtract the year of your birth
The first digit(s) are your shoe size and the last two digits are your age!