Crop to 16x20?

[HGphoto]

Hi there! How do I crop a photo to a 16x20? Lightroom doesn't have this size as an option to crop. 
thank you for the help. 

[Jao vdL]

16x20 is the same aspect ratio as 4x5. Simply crop to that and you will be fine.

[HGphoto]

Thank you. But if I want to print to a 16x20 how to I export so it will be the appropriate amount of pixels?

Sent from my iPhone

[Jao vdL]

You specify this when you export. For example, assuming you are working in the cloud version of Lightroom, Select the image you have just cropped to a 4x5 ratio, then select export from the file menu or click the share button (the square with the arrow going out the top) and select export. For File Type, select JPG, and select custom dimensions. For the long size, calculate the long side of your print times the resolution you want the print to have. This is typically 240 ppi to 300 ppi, so for example a 20" long print should have 20*300=6000 pixels on the long edge. Export your image and you should have a file that you can send to a photolab to print at good quality on a 16x20 size.

The instructions on Lightroom Classic are somewhat different but follow the same principle.

[HGphoto]

This is so helpful thank you. Is the "export Large" option the same
thing? Does it save large enough to print to a 16x20? Or is it always
best to go the "custom" route?

[Jao vdL]

The large setting will export to the actual resolution of the photograph. That should usually work fine but sometimes you either have way too many pixels resulting in very large output files or too few pixels, resulting in blocky pixelated prints. If you specify the size, Lightroom scales the image to the cirrect size which is usually a bit better but you are right that large will almost always work just fine except if you print really large.