You might have seen, some people has large images on their Facebook profile as their profile picture and some other people have tiny profile pictures. Do you want to make your Facebook profile picture as large as possible? It’s easy. Facebook profile picture has no limit on their height. But the width of the picture is limited to 158 pixels. So when you upload a photo with higher width (higher than the height) and do not crop it, then Facebook reduces the width to 158 pixels. As the height is related to the width, to show the image properly, the height again decreases to much lower size. For example, if the width of your photo is 1600 pixels and the height of the picture is 900 pixels, then after uploading it as your profile picture, the width becomes the fixed width size, 158 pixels and the height becomes 89 pixels. So your profile picture looks smaller in size.
So if you upload a portrait picture (taken with holding the camera horizontally), where the height of the image is larger than the width, after uploading, the profile picture will come larger. But if you upload a landspace type photo (taken with holding the camera normally), where the width of the photo is larger than the height of the photo, after uploading, the profile photo will come smaller.
What to do, if you have a landspace type of photo and you want to show your profile picture look larger? In this case, upload the photo to any of the album you have. Then go to that photo page. There you will find an link at the left hand side, below your photo, “Make Profile Picture”. Click on that, crop the required portion of the photo, and make that your profile photo. Make sure, while cropping the photo, make the height larger than the width.