Spirit Level Information

View all spirit and bubble levels from Johnson Level.

A Spirit Level is a tool used to indicate how parallel (level) or perpendicular (plumb) a surface is relative to the earth. A spirit level gets its name from the mineral spirit solution inside the levels.

Typically, the vials in a spirit level are a yellowish-green color with additives for UV protection and maximum performance in temperatures ranging from -20 degrees F to 130 degrees F. The best spirit level is accurate to within plus or minus 0.5 millimeters/meter, or 0.005 inches/inch or .029 degrees. The next level of accuracy displayed is 0.75mm/m or.043 degrees. The vial bodies of a spirit level, also referred to as a bubble level, can be shaped like a barrel, like a rectangular block or even curved, banana-shaped, to measure slope in fractions per foot of pitch; and are mostly made from acrylic today versus glass originally.

How to Read a Spirit Level

  1. Locate the bottom edge of the level. This rests against the surface you're trying to level.
  2. Torpedo level from Johnson LevelSome models feature magnetic edges, which "stick" to metal surfaces for ease of use.
  3. Inspect the body of the level and check for grabbing points where you won't block the vials with your hand(s). 
  4. Most levels feature a punched hole on at least one end for hanging above your workbench.
  5. The tube vial in the center of the level helps you find the true horizontal.
  6. Tube vials on the ends finds the true vertical.
  7. On many torpedo levels and other specialized levels, there is an angled tube vial to find level at 45°.
  8. If your spirit level features an electronic display, consult our guide on how to use a digital electronic level.


How to Use a Spirit Level

  1. Clean the level, removing all buildup and dirt from the edges. 
  2. Mark a line along the bottom edge on the wall.
  3. Flip the level over so that the bottom becomes the top. Put the new top edge along the marked line. If the bubble is centered, your level is accurate. If not, it is defective. 
  4. Place the level on the surface of the object for which you want to find the true horizontal (the “horizon”). Make sure the spirit tube runs parallel to the object. Allow the bubble to float to the top of the spirit tube.
  5. Put your eyes at level with the spirit tube. In order to get an accurate reading, close one eye. 
  6. Take note of where the bubble is inside the spirit tube. If it’s centered between the lines on the tube, your object is level. If the bubble is to the right of the lines, your object slopes downward right-to-left. If the bubble is to the left of the lines, your object slopes downward left-to-right.
  7. To find the true vertical or "plumb," repeat the same process vertically.


How to Check a Spirit Level for Accuracy

  1. Place the level on a flat surface.Yellow box spirit level
  2. Make one mark at the end of the level.
  3. Make another mark along the side of the level, under the vial in the center.
  4. Take a reading of the bubble's position.
  5. Rotate the level 180° end-to-end and align the level with your marks.
  6. Take another reading. If the level is accurate, the bubble will be in the same position for both readings.
  7. To test the vertical vial, follow the same procedure against a flat vertical surface.


Orange torpedo bubble level

How to Level a Scope with a Bubble Level

  1. Ensure your rifle is unloaded.
  2. Place the rifle in a vise, gun cradle, or any other holder keeping the rifle secure.
  3. Place a bubble level on a flat part of the gun. If you have a second spirit level, use it on another flat part, such as the action, above the chamber or on the rib.
  4. Tighten the rifle in place when you reach level. 
  5. Place the scope in the rings.
  6. Tighten the scope snug, but loose enough to be able to shift it slightly.
  7. Place a bubble level on the scope and level the scope horizontally.
  8. Rotate the level parallel to the scope and level it vertically.
  9. Your scope is now level.


How Spirit Levels are Made

Spirit levels are made from a variety of materials including aluminum, plastic, wood, cast iron and composite materials. Users of spirit levels are categorized as professional contractors and tradesman, such as carpenters, masons, framers, electricians, plumbers and woodworkers; and do-it-yourselfers, such as a homeowner.

Types of Spirit Levels

There are a variety of spirit level styles for tradesman and contractors to chose from, the most popular being I-beam levels (the level frame is an "I" shape when looking at its end), box beam levels (the level frame is a rectangle shape) and torpedo levels (slightly bigger than pocket-sized, 9" to 12" 3-vial levels). Other spirit level styles include: line levels (single vial with a hook to hand on a string), cross check levels (pocket size; two level vials at right angles), circular levels (surface levels), pocket levels (pen shaped with a magnetic tip) and post levels (wraps around two sides of a post to measure level and plumb).

Check out the following how-to instructionals regarding specialized spirit levels:

There are other functional spirit level features beyond style and material such as magnetism, vial type and durability. Some spirit levels are magnetic which are ideal for construction with metal studs, or a plumber or electrician working around pipes and conduit. Magnet strength versus a spirit levels weight is an important test for quality; rare earth magnets are the strongest. Some spirit levels have replaceable vials, such as i-beam levels with barrel shaped vials which are set into the frame, or wood levels with banana-shaped vials. Block vials on box beam levels are machine set and cannot be replaced with the same accuracy as provided by the factory. Spirit levels are also made more durable with the inclusion of vial covers to protect the vial and end-caps to withstand the shock of being dropped. Some spirit levels have hand grips, which are primarily for comfort.

For other handy sets of instructions on proper level use, visit Johnson Level’s how-to guide.

View all spirit and bubble levels from Johnson Level.