Here's how to convert 5 feet 3 inches to millimeters:

1. Convert feet to inches:

* 5 feet * 12 inches/foot = 60 inches

2. Add the remaining inches:

* 60 inches + 3 inches = 63 inches

3. Convert inches to millimeters:

* 63 inches * 25.4 mm/inch = 1600.2 mm

Therefore, 5 feet 3 inches is equal to 1600.2 millimeters.