Maybe you're wanting to figure the slope of a driveway, a sanitary or storm sewer pipe, a parking lot, a handicap accessible ramp or the slope of a drainage ditch?  Some people use the term slope (degree of angle) and people use percent.

If you take a ruler, pencil or stick and lay it on the desk, that's zero percent slope.  Now hold the object straight up.  Straight up is  100% slope.  A 45 degree angle of the pencil is 50% slope.  1 or 2% slope is popular for many drainage applications.

Many times slope plays a much more important role in design and in our lives in general than most people ever realize.  The American with Disabilities Act (ADA) sets and enforces regulations with design criteria such as the slope of parking lots, sidewalks and ramps.  The MD Smart Levels work great for this application.

Sanitary sewer lines are usually installed at a 2% slope so the water doesn't out run the solids resulting in a clogged sewer line.  The Leica Piper or the Topcon TPL series are both great Pipe Lasers that are widely used for this application.

MD Smart LevelTopcon TPL Pipe Laser