+ (CGFloat)statusBarHeight {
    if ( @available(iOS 13.0, *)) {
        NSSet *set = [UIApplication sharedApplication].connectedScenes;
        UIWindowScene *windowScene = [set anyObject];
        UIStatusBarManager *statusBarManager = windowScene.statusBarManager;
        CGFloat statusBarHeight = statusBarManager.statusBarFrame.size.height;
        if( @available(iOS 16.0, *)) {
            BOOL needAdjust = (statusBarHeight == 44);
            if(windowScene.windows.firstObject.safeAreaInsets.top == 59 && needAdjust) {
                statusBarHeight = 59;
            }
        }
        return statusBarHeight;
    }
    CGFloat statusBarHeight = [UIApplication sharedApplication].statusBarFrame.size.height;
    CGFloat safeAreaTop = UIApplication.sharedApplication.windows.firstObject.safeAreaInsets.top;
    return MAX(statusBarHeight, safeAreaTop);
}

[UIApplication sharedApplication].statusBarFrame.size.height. But since all sizes are in points, not in pixels, status bar height always equals 20.

Update. Seeing this answer being considered helpful, I should elaborate.

Status bar height is, indeed, equals 20.0f points except following cases:

• status bar has been hidden with setStatusBarHidden:withAnimation: method and its height equals 0.0f points;
• as @Anton here pointed out, during an incoming call outside of Phone application or during sound recording session status bar height equals 40.0f points.

There's also a case of status bar affecting the height of your view. Normally, the view's height equals screen dimension for given orientation minus status bar height. However, if you animate status bar (show or hide it) after the view was shown, status bar will change its frame, but the view will not, you'll have to manually resize the view after status bar animation (or during animation since status bar height sets to final value at the start of animation).

Update 2. There's also a case of user interface orientation. Status bar does not respect the orientation value, thus status bar height value for portrait mode is [UIApplication sharedApplication].statusBarFrame.size.height (yes, default orientation is always portrait, no matter what your app info.plist says), for landscape - [UIApplication sharedApplication].statusBarFrame.size.width. To determine UI's current orientation when outside of UIViewController and self.interfaceOrientation is not available, use [UIApplication sharedApplication].statusBarOrientation.

Update for iOS7. Even though status bar visual style changed, it's still there, its frame still behaves the same. The only interesting find about status bar I got – I share: your UINavigationBar's tiled background will also be tiled to status bar, so you can achieve some interesting design effects or just color your status bar. This, too, won't affect status bar height in any way.

You should never hardcode the exact value of the height at any point in your code.

As long as you use default UI components (UINavigationController / UITableView / UICollectionView / etc.) you usually don't need to worry about the status bar height at all. These ViewControllers should layout correctly on any device and any orientation.

If you do have custom layout needs, you should refer to the safeAreaLayoutGuide on UIView, instead of hardcoding a height: https://developer.apple.com/documentation/uikit/uiview/2891102-safearealayoutguide?language=objc

But to make this answer complete - the size of the status bar is different on different devices and different orientations:

• Most devices up to the iPhone X have a 20pt height in portrait & landscape.
  (20px, 40px, 60px in @1x, @2x, @3x)
• On iPhone X in portrait it's 44pt (so 44px, 88px, 132px accordingly).
  In landscape the height is different though.

As the warning hints, you can access the statusBarManager which has a statusBarFrame property. This is defined on your UIWindow's windowScene.

let height = view.window?.windowScene?.statusBarManager?.statusBarFrame.height ?? 0

If you're using Expo you can use Constants.statusBarHeight.

import Constants from 'expo-constants';
const statusBarHeight = Constants.statusBarHeight;

If you're using Vanilla React Native with React Navigation you can use the following:

import { useSafeAreaInsets } from 'react-native-safe-area-context';
const insets = useSafeAreaInsets();
const statusBarHeight = insets.top;

See: https://reactnavigation.org/docs/handling-safe-area/#use-the-hook-for-more-control

Sample Code:

import * as React from 'react';
import { Text, View, StatusBar } from 'react-native';
import Constants from 'expo-constants';
import { useSafeAreaInsets, SafeAreaProvider } from 'react-native-safe-area-context';

export default function App() {
  return (
    <SafeAreaProvider>
      <ChildScreen />
    </SafeAreaProvider>
  );
}

function ChildScreen() {
  const insets = useSafeAreaInsets();
  
  return (
    <View style={{ flex: 1, justifyContent: 'center'}}>
      <Text>
        {insets.top}
      </Text>
      <Text>
        {Constants.statusBarHeight}
      </Text>
      <Text>
        {StatusBar.currentHeight ?? 'N/A'}
      </Text>
    </View>
  );
}

Output:

Live code: https://snack.expo.dev/@dcangulo/statusbarheight