YOU GET 72 BUILT-IN SCALES for versatility, 39 imperial (feet-Inch) and 33 metric; Multiple units; decimal feet, feet-inches, decimal inches, yards, millimeters, meters, kilometers; square and cubic formats PLUS 6 CUSTOM SCALES, 3 each for imperial and metric units; you can define any scale from plans that have been reduced, enlarged or are otherwise out of scale; calibrates to any plan and stores that scale SO YOU CAN DO TAKEOFFS ANYWHERE with no cable or PC required; use it on jobsites, in your office or on the hood of your truck to get takeoffs for estimates and get material orders when you need it AND CALCULATE AREA AND VOLUME - roll length and width to get area. Set height to get volume. Use either imperial or metric units; just roll and store values with dedicated keys; display shows answers clearly. Based on start and stop point accuracy and scale magnitude, most users typically experience +/- 2%-3% rolling error. MANUALLY COUNT items while rolling a set of plans to