Normally, the original size (resolution) of an image generated by a digital camera is 6000×4000 px for landscape mode and 4000×6000 for portrait mode. If you want to use an image for a blog post, design, or social media, you definitely need to resize it first. Photoshop has the capability to make the very basic editing like resizing an image. In case you are new to Photoshop, this post will show you how.
First off, launch Photoshop on your computer and open the image you want to resize by clicking the File menu and select Open. Or, you can simply press the Ctrl+O keys on the keyboard if you use Windows (more Photoshop shortcuts).

Once your image opens, click the Image menu and select Image Size. This will open the Image Size box.

On the Image Size dialog box, enter your preferred size. You can enter the width of the image on the Width field and the height of the image on the Height field.

By default, the Constrain Proportions option is enabled. You can keep this option enabled if you want to maintain the original aspect ratio (ratio of width to height measurement) of your image. Conversely, if you want to scale the width and height independently of each other, you can disable the Constrain Proportions option by clicking the chain icon to unlink them.

Photoshop itself actually offers preset sizes you can choose from. To use a preset size, you can click the dropdown menu on the Fit To option.

If you want to change the unit of measurement for the pixel dimension, you can click the dropdown menu on the Dimensions option. You can change the unit from pixels to inches, centimeters, millimeters, or percent.

On the bottom section, you can also select your preferred resampling method. There are 6 resampling methods you can choose from. If you have no idea about resampling, you can simply select Automatic.
Once done setting all of the required parameters on the Image Size box, click the OK button to apply the new size.

Note: Photoshop doesn’t display the entire image area on the preview panel on the Image Size box. If you want to see the entire area, you can hover your mouse over the image and zoom-out the image by clicking the minus icon.
To export the resized image, open the File menu and select Export -> Export As (Alt-Shift+Ctrl+W).

On the Export As dialog box, simply click the Export button.
