In Photoshop and PSE, sometimes size does matter. When you have opened a photo or document and need to know the size, press Ctrl + Alt + I (Mac: Cmd + Opt + I) to activate the Image Size Dialog box.
This box gives you the current dimensions of your document and allows you to change the size on the fly.
In the Document Size section, you can quickly change the size, but remember that sizing UP can adversely affect the resolution of your photo. Be sure to click the Constrain proportions box to maintain the aspect ratio and avoid the funhouse effect.
Click OK to confirm the size change.