How do I resize an image?

1. As a rule, you should try very hard not to change the pixel dimensions of your image without changing the resolution. Doing so requires Elements to either add or subtract pixels using a “best guess” procedure known as resampling.
2. To resize without resampling, choose Image > Resize > Image Size. In the dialog box that appears, deselect the Resample Image checkbox at the bottom of the box. As soon as you do this, the Pixel Dimensions portion of the dialog box will be grayed out. This is good. Make sure the Constrain Proportions box is checked.
3. If you have a target resolution that you want for your image, change the Resolution text box to that setting. 300 ppi is a reasonable setting for an inkjet printer. Anything less than 200 ppi will probably give a poor quality result. If you are planning on printing this image on the same sheet of paper as other images, you will want to make them all the same resolution.
4. You will notice that changing the resolution changes your Document Size dimensions. Increasing the resolution decreases the size. Decreasing the resolution increases the size.
5. If you are unable to get the desired dimensions at the resolution you want, you may then resort to resampling. Moderate resampling down (to smaller pixel dimensions) is not too bad. Resampling up should be avoided at all costs.
6. To resize with resampling, select the Resample Image checkbox. Choose Bicubic from the menu to the right of the checkbox. Make a note of the pixel dimensions showing at the top of the dialog box. This is important. You do not want to end up with settings that show an increase in pixel dimensions. Make sure the Constrain Proportions box is checked.
7. Now, set your target resolution in the Resolution box, and then set your Document Size dimensions to what you are after. You will notice that changing one dimension also changes the other. This is because Constrain Proportions prevents disproportional resizing of the image which would result in distortion.
8. If your image is intended for use on the Web, and not for printout, disregard all of the above. Simply open the Resize Image dialog box, make sure Resample Image is checked and set to Bicubic, make sure Constrain Proportions is checked, set your resolution to 72 ppi and use the Pixel Dimensions setting at the top of the box to resize to the desired dimensions.
9. If, in the course of using the Resize Image dialog box, you get confused and want to start over, press the Alt key. The Cancel button will change to be a Reset button. Click on that and try again.
10. For an explanation of print and screen resolution, please see the Resolution page in the Photoshop section of this site.