Which Is More Accurate, a Plumb Bob or Level?

A carpenter uses a level to determine if a jamb is plumb.

If used for their intended purposes, plumb bobs and levels are equally accurate. However, levels and plumb bobs become inaccurate and useless if applied improperly. Learn the functions and applications of both tools, and you can choose the right one for your project.

Plumb Bobs

A plumb bob's tip is precisely aligned with its string.

The term plumb refers to a plane that runs straight up and down. The plumb bob's function is to determine a perfectly plumb path between two points. The plumb bob consists of an upside-down teardrop weight attached to a string. To use a plumb bob, the builder holds the string at an elevated point, drops the weight and allows the weight to swing to a stop.

Levels

Levels determine a surface's vertical or horizontal position relative to the earth's true horizon. Levels use a bubble encapsulated in a liquid-filled vial to show the slope of a surface. Because the level's shape is similar to a flat-sided, rectangular bar, the level is most accurate when gauging the position of flat surfaces.

The Right Tool for the Job: Plumb Bob or Level

Plumb bobs are more accurate than levels for determining a perfectly vertical path, such as the beginning and end points of a plumbing vent pipe. Levels are more accurate than plumb bobs for gauging the plumb of flat surfaces, such as a vertically positioned piece of lumber. Of the two tools, only a level can gauge the horizontal position of a surface, such as the top of a stud wall.

References

• University of Wisconsin, Steven's Point: Plumb Bob