[header] How to measure a mattress [title] Take off any sheets, blankets, or pillows on your mattress. [step] You'll get the most accurate measurements when your mattress doesn't have anything on it. If you're measuring your mattress for fitted sheets or a comforter, and you have a padded mattress topper on your mattress, leave it on when you do the measuring. 
[title] Measure from the left side to the right side of your mattress to get the width. [step] Use a tape measure or fabric ruler to do your measuring.