Is 6.4 stone underweight for a 5 foot girl?

Yes, 6.4 stone (approximately 89 pounds) is generally considered underweight for a 5-foot tall girl. According to the Body Mass Index (BMI) scale, a healthy weight range for someone of that height is typically between 97 to 128 pounds. It's important to consult with a healthcare professional for personalized advice regarding weight and health.