LayerCompass Tool
Skew & Squareness Calculator
Your test square has roughly correct side lengths but still looks slightly “slanted”? Skew may be the reason. This tool explains what to print, where to measure and how to interpret the result step by step.
In plain English
When do you need this tool?
Typical case: A rectangular part measures close to correct along X and Y, but its corners are not exactly 90°. The two diagonals will then be different lengths.
If the whole part is simply too large/small, holes do not fit, or dimensions vary randomly, skew is probably not the first thing to fix.
5 simple steps
How to use the calculator
- Print a skew calibration object.For most users, start with the XY plane – squareness across the build plate. XZ/YZ are mainly for specific vertical geometry issues.
- Disable skew correction for the test print.With Klipper, for example, use
SET_SKEW CLEAR=1. Otherwise you would measure geometry that is already being corrected. - Measure three distances with calipers.AC = first diagonal, BD = second diagonal, AD = one side. Do not include any corner flats when measuring AD.
- Enter the values below.Ideally measure each distance 2–3 times. Small measurement errors can noticeably affect the result.
- Understand the result before correcting anything.If the printer is visibly out of square, improve the mechanics first. Software skew correction is fine adjustment, not a substitute for loose or badly aligned hardware.
The measurement method follows Klipper's official skew documentation. Open Klipper documentation ↗
1. Choose a plane & 2. enter measurements
For most users: Leave the plane on XY. XZ and YZ are only needed when you specifically want to check squareness relative to Z.
No measurements yet
Enter AC, BD and AD from the calibration object. If you only want to try the workflow, load Klipper's official example.
When is skew probably not your problem?
All dimensions are consistently too small/large
Check material shrinkage or scaling instead.
Holes do not fit but outer dimensions do
Check hole/contour compensation or designed clearance instead.
The error is random or only affects some layers
Check mechanics, belts, layer shifts, collisions or extrusion.
The part lifts at the corners
That is warping and it can invalidate diagonal measurements.
Rule of thumb: Skew means the geometry is systematically slanted even though the side lengths look plausible.
Tool guide
Skew & Squareness Calculator: when and how should you use it?
A useful result starts with the right question. These notes explain what the tool is designed for, how to interpret its output and where a calculation is intentionally only an approximation.
When should you use this tool?
Use it when a rectangular print has plausible side lengths but is not truly 90° square, or when the two diagonals measure differently. The tool explains the measurement process step by step.
How to use it well
For most printers, start with XY. Print a calibration object with skew correction disabled, measure diagonals AC/BD and side AD as shown in the diagram, and repeat each measurement if possible.
Limits & important notes
Skew is a systematic angular error. This tool is not intended for warping, random layer shifts, simple material shrinkage or incorrect flow. Correct visibly poor mechanical squareness first where practical.
Frequently asked questions
What exactly do I measure?
Only three distances on the skew calibration object: AC and BD are the two diagonals, while AD is one side. The tool page shows A/B/C/D in a diagram.
Which plane should I choose?
XY in most cases. It checks whether the X and Y axes are truly square across the build plate. XZ/YZ are mainly for specific vertical geometry checks.
Should I always correct skew in software?
No. Repeat the measurement and inspect the mechanics first. Klipper recommends improving significant mechanical skew before using software correction as fine adjustment.
Can I use the tool without Klipper?
Yes for evaluating the geometry and angular error. The generated SET_SKEW and CALC_MEASURED_SKEW commands are Klipper-specific.
These tools provide guidance and calculations from your inputs. Safety-critical, electrical or highly loaded parts require additional verification.
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