Use a coin or a credit card to calibrate the ruler anywhere, when you don't have a real ruler with you! - Ad free, for real, forever! - Pick your units: fractional inches, decimal inches, centimeters or millimeters - Calibrate your ruler with a credit card to get you started anytime, anywhere - Don't have a credit card with you? Calibrate your ruler with a coin! - Calibrate your ruler with a real ruler to achieve the best precision in your measurement transfers - Manually set the ruler to a known length for accurate measurements - Night mode to save battery (on AMOLED screens) and to relieve your eyes at night - Save your measurements for future use - No permissions required