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How to Check Your Laser Level's Accuracy on the Jobsite
How to Check Your Laser Level's Accuracy on the Jobsite
Short answer: use the two-wall test. It takes about ten minutes, needs a tape measure and a pencil, and shows whether your laser's error is within its stated accuracy. Check any new tool, any tool that has been dropped, and any tool before critical work.
What you need
- Two walls about 30 feet apart (a large room or hallway works)
- A tripod or a stable surface, a tape measure, and a pencil or tape for marks
- The laser's spec sheet, for its stated accuracy (for example, 1/8 inch at 30 feet)
Level check: the two-wall test
- Set up in the middle. Place the laser halfway between wall A and wall B. Turn it on and let it self-level.
- Mark the first points. Mark where the horizontal line hits wall A (call it A1) and wall B (B1). Measure the height difference between A1 and B1.
- Move next to wall A. Put the laser about one foot from wall A, at about the same height. Let it self-level.
- Mark again. Mark the beam on wall A (A2) and wall B (B2). Measure the height difference between A2 and B2.
- Compare. Subtract the first difference from the second. That result is your error over the distance between the walls.
Why it works: from the midpoint, any error hits both walls equally, so the A1 to B1 difference shows the true height difference. Next to wall A, the error over the full distance shows up only at the far wall. The change between the two is the error.
Reading the result
| Result | What to do |
|---|---|
| Error is within the stated accuracy at that distance | The laser is good. Log the date. |
| Error is outside the stated accuracy | Repeat once to rule out a setup mistake. If it repeats, stop using it for precise work and request calibration or service. |
The error scales with distance. A tool that is off by 1/8 inch at 30 feet will be off by about 1/4 inch at 60 feet.
Plumb check
Hang a plumb bob from a high point (a ceiling or scaffold), let it settle, and shine the vertical line beside the string. The line should match the string along its length. Check both vertical lines on a cross-line laser.
Rotary lasers
Rotary lasers use the same idea, known as the two-peg test: set up midway between two stakes, take a rod reading at each; move the laser near one stake, take both readings again, and compare the differences. Check the manual for the exact procedure and the stated tolerance.
When to check
- When the tool is new
- After a drop, a hard knock, or transport in a vehicle without a case
- Before critical work, and periodically (many crews check monthly)
- Each time the tool is returned from service
Frequently asked questions
How often should a laser level be calibrated?
Follow the manufacturer's guidance. Many professional crews have calibration done yearly and check on the jobsite in between.
Can I adjust the laser myself?
Only if the manual describes a user calibration. Otherwise send it for service, since opening it may void the warranty.
What if the two-wall test fails?
Make sure the tool was on a stable, level-enough surface and self-leveled before each mark, then repeat. If it still fails, request service.
Request calibration or service, or browse Beiter laser levels.
