The appropriate length for your resume depends on several factors. The most important thing to keep in mind is to make sure your wording is concise, to the point, and is not redundant.
Write your resume without paying attention to the length first. Once you have the content in place you can edit it to fit nicely on the page(s), deleting extraneous information where needed.
Padding your resume to try to look like you have done a lot by including irrelevant information is likely to backfire. If a significant portion of the material you list is not going to demonstrate your qualifications or significant accomplishments, you are more likely to be showcasing that you are not the right person for the job.
One-Page Resume: If you are new to the job market and lack a long work history, then a single page resume is likely sufficient. In many cases, the same can be true if you have only one or two employers for whom you have worked in the same role for many years. If you find yourself struggling to find the skills and accomplishments to fill the space, don’t force it beyond a single page.
Two-Page Resume: The most common resume these days is two pages in length. If you are established in your line of work, and have 3 or more significant past employers, two pages is probably right. If you are new to your career, but have significant academic or technical training, then a two page resume may also be right for you.
Three-Page Resume: There are some cases where a three page resume is appropriate, but they are rare. Academic jobs such as professor generally expect a C.V. instead of a resume. This special class of resume includes many additional sections not listed on a traditional resume, such as publications. In addition, senior level executives may have enough relevant job experience in a variety of roles to justify three pages. Finally, if you are applying to a position abroad, check with the resume expectations in that country since some will expect a longer form resume than employers in the States.