How do I make pictures larger in iPhoto

If you are using the editor that comes with iPhoto, you can try this.

Make sure you are viewing your photo with the information visible in the lower left hand corner of iPhoto. If it isn't there, click on the lower case i encased in a blue circle (lower left corner). Now you can see the dimensions of your original photo.

Next, right click on the photo and select edit. This will open the editor. Choose crop and you will see a line of options starting with a check box and Constrain: (original) Select that drop down menu and you will see how you can enlarge your photo to many different sizes. Everything from 2 x3 to custom. Choose one and then click on Done. You will be taken back to the main view of your photo. Info should show you the size of your photo has changed (depending on what dimensions you selected). I tried this with a picture and had to run thru the steps a few times to make my picture significantly larger -- but it works.

Good Luck

Are you wanting to create a larger pixel dimension for a photo that it has originally? The only way to do that is with a 3rd party editor like Photoshop Elements and resize the image using the Bicubic Smoother pixel resampling method for image resizing beyond it's original pixel dimensions. PSE can do a fairly reasonable job. I've upsized photos that were only slightly mottled in appearance. But the upsize wan't a whole lot.

OT

TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto (iPhoto.Library for iPhoto 5 and earlier versions) database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger or later), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. There are versions that are compatible with iPhoto 5, 6, 7 and 8 libraries and Tiger and Leopard. Just put the application in the Dock and click on it whenever you want to backup the dB file. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.

NOTE: The new rebuild option in iPhoto 09 (v. 8.0.2), Rebuild the iPhoto Library Database from automatic backup" makes this tip obsolete.