I have a photo that I want to put in a printed calendar. It's of 2 lorikeets and one is hanging upside down. One of my best shots. But the photo is a paltry 1280x960, taken in early 2000s when my Olympus camera was new and I didn't realise one day I might want some photos big for printing. Not very intelligent on my part. I searched for an online resizer and there it was.
Check it out at: http://www.simpleimageresizer.com/upload#.VG6c2_mUd0Y
Try it. You'll love it.