One page if you have fewer than 10 years of experience. Two pages is acceptable at 10 or more years, or in senior and technical roles where the work genuinely needs the space. Three pages is reserved for academic CVs and federal resumes, which follow entirely different conventions. Paste your resume into the checker above for an instant word count, page estimate, and a verdict against your own experience level, instead of guessing.
Length is not really the question worth asking. The real question is whether every line on the page is earning its place, and the page count is just the symptom that shows up when it is not.