Flutter - How to get this GPA Calculator working?

Question

I'm trying to create a GPA Calculator app. The problem I'm facing is that I don't know how can I do some calculation (all courses points/number of courses) and then print the value in a text widget. I'm using a text controller for each field, but I need help to display the values. I created a future void but i dont know how to display the value in a text widget. Please check the picture of the app below:

class GPA_Calc extends StatefulWidget {
  const GPA_Calc({super.key});

  @override
  State<GPA_Calc> createState() => _GPA_CalcState();
}

class _GPA_CalcState extends State<GPA_Calc> {
  
  final c1 = TextEditingController();
  final c2 = TextEditingController();
  final c3 = TextEditingController();
  final c4 = TextEditingController();
  final c5 = TextEditingController();
  final c6 = TextEditingController();

  Future<double> calgpa() async {
    late int cv1 = int.parse(c1.text);
    late int cv2 = int.parse(c2.text);
    late int cv3 = int.parse(c3.text);
    late int cv4 = int.parse(c4.text);
    late int cv5 = int.parse(c5.text);
    late int cv6 = int.parse(c6.text);
    var gpa = (cv1+cv2+cv3+cv4+cv5+cv6)/(6) ;
    return gpa;
 }


  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            onChanged:(value) => 0,
            keyboardType: TextInputType.number,
            controller: c1,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 1 Credit Points"
            ),
          ),
        ),
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            keyboardType: TextInputType.number,
            controller: c2,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 2 Credit Points"
            ),
          ),
        ),
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            keyboardType: TextInputType.number,
            controller: c3,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 3 Credit Points"
            ),
          ),
        ),
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            keyboardType: TextInputType.number,
            controller: c4,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 4 Credit Points"
            ),
          ),
        ),
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            keyboardType: TextInputType.number,
            controller: c5,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 5 Credit Points"
            ),
          ),
        ),
        Padding(
          padding: EdgeInsets.all(10),
          child: TextField(
            keyboardType: TextInputType.number,
            controller: c6,
            decoration: InputDecoration(
              border: OutlineInputBorder(borderRadius: BorderRadius.circular(15)),
              hintText: "Enter Course 6 Credit Points"
            ),
          ),
        ),
       Text('How can I display the calculated value here??')
      ],
    );
  }
}

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