How to Calibrate a Spirit Level

How to Calibrate a Spirit Level

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Spirit levels, aka bubble levels, are of course one of the most useful tools for leveling and straightening various construction projects.

That being said, one of the things that many people don’t think about is that spirit levels themselves need to be calibrated and checked for accuracy. Let’s talk about why this is the case and how to do it.

Can a Spirit Level Be Wrong?

The simple fact of the matter is that yes, spirit levels can be wrong. Sure, they usually come completely accurate right out of the box because they’re generally calibrated right from the get-go. However, just like many other measuring tools out there, spirit levels can become less accurate over time, or in other words, they go bad.

Obviously, if a spirit level is wrong, you are going to run into big-time problems, especially when it comes to large construction projects where various surfaces need to be totally level so they meet each other with great precision.

That said, just because the spirit level is no longer accurate does not mean that you need to throw it out. Spirit levels can be calibrated, which means that if yours starts to be inaccurate, there is something you can do about it. On an important side note, some spirit levels may not be calibrated out of the box and may require you to calibrate them before you use them the first time.

Calibrating a Spirit Level

How to Tell If Your Spirit Level Is Inaccurate

OK, so what you’re probably wondering here is how you can actually tell if your spirit level is inaccurate. After all, a spirit level is a tool used to measure leveling accuracy, so how do you measure the accuracy of a measuring tool? It’s quite the conundrum indeed, but that said, it is totally possible to do. Let’s go through a quick step-by-step process on how to tell if your spirit level is inaccurate.

Keep in mind that the following method of measuring the accuracy of your bubble level can be used both for vertical leveling and horizontal leveling. Remember, a good spirit level can be used to level both walls and floors, which means that they have little vials filled with water and air to measure both floor level and wall plumb.

The methods to tell if your spirit level is vertically and horizontally accurate are the same, with the only difference being that when you are looking at the accuracy for vertical plumb, you have to hold the level vertically against a wall or pole and to check the horizontal accuracy of it, you need to lay it down on a flat horizontal surface.

With that out of the way, here’s the accuracy checking process:

  1. Hold the level against a flat wall or place it on a flat surface
  2. Make sure to take note of where along the wall, floor, or surface the vial of the level is.
  3. Look at the vial and take note of where the bubble is (make sure that you are looking at the appropriate vial).
  4. Turn the bubble level 180-degrees, or in other words, just turn it around.
  5. If the bubble level is accurate, the bubble will be in the exact same position within the vial whether the bubble level is facing one way or the other.
  6. If the bubble is not in the same position within the vial for both directions, then your bubble level is inaccurate.

Do Digital Spirit Levels Need to be Calibrated?

Although many think that digital spirit levels are totally perfect, because hey, they use the technology, the fact of the matter is that no, they’re not always perfect, and yes, sometimes they do need to be calibrated.

Digital spirit levels should always come completely calibrated out of the box, so you shouldn’t have to calibrate one right when you buy it, but that said, they can become inaccurate overtime. Calibrating a digital spirit level involves using the automatic calibration feature that they come with.

Exactly how these calibration features work is going to depend on the exact model and make of digital spirit level, so this is not something that we’re going to explain. However, if you have a digital spirit level and you need to calibrate it, then all you really need to do is read the owner’s manual. Realistically, it should only involve two or three steps.

Digital Spirit Level Calibration

How to Calibrate a Spirit Level

What we want to do right now is to provide you with a step-by-step instructional on how to calibrate this manual spirit level. It’s actually quite easy.

Step 1: Find a Level Surface

OK, so before you begin the big trick here is that in order to calibrate your bubble level, you need to have a surface that is already 100% level. If the surface that you are using to calibrate your spirit level is itself not level, then there is no way that you can accurately calibrate the spirit level. By all means, you must absolutely find a surface that you are 100% certain is already leveled.

Step 2: Lay the Spirit Level

Once you have found the level surface, lay the spirit level down onto that surface. Now you need to take note of where exactly within the wild the bubble rests. If the bubble is not exactly in the center of the vial, then you know that the bubble level is inaccurate.

Once again, keep in mind that the only way to tell if the bubble level is inaccurate by looking at the bubble within the vial is if the surface below is already 100% level. It is very important for us to stress the fact that you cannot calibrate a bubble level if the surface you are using to calibrate it is not level itself.

Step 3: Adjust the Screws

On your bubble level, beside each of the vials you will see a little screw. These are the calibration screws used to calibrate the spirit level. So, keeping in mind that the surface below needs to be totally level, if the bubble in the vial is off-center, adjust the screw until the bubble is perfectly centered in between the two lines in the vial.

Once you have adjusted the screws so that the bubble is in the middle of those two lines, your level is calibrated.

Mistakes to Avoid, Tips & Tricks

Lastly, let’s provide you with a few quick tips to help make your life a little bit easier:

  • Although you really should not have to, it is a good idea to check your spirit level for accuracy out of the box. You don’t want to use a new level to build something, just to figure out that it was inaccurate all along.
  • If you are calibrating a spirit level, always follow the user’s manual, as not all of them have those calibration screws. A really low-end bubble level might not allow you to calibrate it at all.
  • The simple fact here is that you do often get what you pay for, so we do not recommend going for the cheapest possible option. A cheap spirit level is much likelier to be inaccurate right from the get-go.


The bottom line here is that you need to make sure that your spirit level is properly calibrated at all times. If it is not, whatever you build is going to end up being crooked and wonky.