Dynamid PieChart size

main.dart

import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'FlChart Demo',
      showPerformanceOverlay: false,
      theme: ThemeData(
        primaryColor: const Color(0xff262545),
        primaryColorDark: const Color(0xff201f39),
        brightness: Brightness.dark,
      ),
      home: Scaffold(
        body: SafeArea(
          child: LayoutBuilder(
            builder: (context, BoxConstraints constrain) {
              final shortSize = constrain.biggest.shortestSide / 2;
              return PieChart(
                PieChartData(
                  sections: [
                    PieChartSectionData(value: 10, radius: shortSize),
                    PieChartSectionData(value: 10, radius: shortSize),
                    PieChartSectionData(value: 10, radius: shortSize),
                  ],
                  centerSpaceRadius: 0,
                ),
              );
            },
          ),
        ),
      ),
    );
  }
}

Made for this issue

very helpful