Blender can measure in both its default setting (Blender units) and both metric and Imperial. You make this setting in the "scene" tab in the function settings in the right hand panel (where materials/textures/modifiers are located. In the 3d viewport, if you punch in the "n" key, it brings up properties, which will give you actual measurements in these different modes. it is good practice to never scale or rotate in object mode, but do so in edit mode. Doing so in object mode wiill throw scale and rotation off and your measurements will not be accurate. By scrolling the mouse wheel in the 3d viewport while in ortho mode, you can watch in the upper left as measurements change from inches to feet to yards. Each square is a unit of measurement. Easy peasey lemon squeezy. Give it a try...

HTH

C~