3D Print Dimensional Compensation Calculator
Use two measured calibration features to work out the CAD dimension needed for a required printed size. The two-point model separates proportional size change from a repeatable fixed offset.
Recommended CAD dimension (mm)50.43
- Target-specific model scale
- 100.86%
- Proportional scale correction
- 100.76%
- Proportional shrinkage
- 0.75%
- Fixed dimensional bias (mm)
- -0.05
- Residual error with scale-only correction (mm)
- -0.05
- Suggested correction approach
- X-axis outside-dimension results need more than proportional scaling alone. Test separate contour compensation or a CAD feature offset after applying the scale correction.
Fits one straight-line response for the selected axis and feature type; use matching print settings and measurement method for both features.
How to use this calculator
- Choose one axis and one feature type, then use two calibration features printed with matching settings and orientation.
- Enter the modeled and cooled, measured sizes for a small and a substantially larger feature.
- Enter the finished size you need for the production part.
- Use the recommended CAD size first, then test any separate scale or contour and hole corrections on another print.
How two-point dimensional compensation works
A one-size calibration print can tell you that a part came out small or large, but it cannot tell whether the error is proportional to size or is a near-constant offset. Those errors behave differently. A 1% shrinkage changes a 100 mm part by about ten times as much as a 10 mm part, while a fixed contour or hole offset can miss both features by a similar number of millimeters.
This calculator fits a straight-line response for one axis and one feature type:
m = a * d + b
Here, d is the CAD dimension, m is the expected printed measurement, a is the proportional response, and b is the fixed dimensional bias. From two calibration features, the slope and intercept are:
a = (m2 - m1) / (d2 - d1)
b = m1 - a * d1
For a required finished size T, the tool reverses that line to find the CAD dimension:
dT = (T - b) / a
The proportional scale correction is 100 / a percent and proportional shrinkage is 100 * (1 - a) percent. The target-specific model scale may differ from the proportional scale because it includes the fixed bias. If only scale is applied, the fitted fixed bias remains as the expected residual error.
How to use the result
Use features that are far enough apart for the difference to exceed normal caliper rounding and print variation. Measure after the part has cooled, with the same caliper technique for both features. Keep filament, orientation, temperatures, cooling, wall settings, and first-layer conditions the same as the part you plan to make.
Calibrate X, Y, and Z independently when the workflow allows it. Also keep outside dimensions separate from holes or openings. OrcaSlicer, for example, provides different X-Y contour and hole compensation controls; they can move features differently from whole-model scaling. A nontrivial fixed bias is a reason to test one of those feature-specific settings or a CAD offset rather than relying on scale alone.
What the estimate leaves out
The fitted line is an approximation over the two calibration sizes, not a complete printer model. It does not independently correct elephant foot, skew, warping, first-layer squish, nozzle width effects, flow error, or local geometry. Z dimensions can also be quantized by layer height rather than following a smooth line.
Predictions outside the measured range are extrapolations and can be unreliable. Confirm an important clearance, press fit, or overall size with a second print before changing a printer-wide or filament-wide profile.
Worked example
Suppose an X-axis outside feature designed at 20 mm measures 19.80 mm, and a 100 mm feature measures 99.20 mm. The fitted slope is (99.20 - 19.80) / (100 - 20) = 0.9925. The fixed bias is 19.80 - (0.9925 * 20) = -0.05 mm.
For a required 50 mm finished size, the recommended CAD dimension is (50 - -0.05) / 0.9925 = 50.43 mm. The target-specific model scale is 100.86%, the proportional scale correction is 100.76%, and the proportional shrinkage is 0.75%. Applying only the proportional correction would retain the fitted -0.05 mm bias, so a contour adjustment is worth testing if the tolerance requires it.
Common questions
Why use two calibration sizes instead of one calibration cube?
One calibration size gives a single ratio, so it cannot separate a proportional response from a fixed dimensional bias. Two different sizes define a straight-line model with both a slope and an intercept. That makes the CAD correction more useful when the production dimension differs from the calibration feature.
What is the difference between shrinkage and X-Y compensation?
Proportional shrinkage changes with feature size and is represented here by the slope of the fitted line. X-Y contour or hole compensation is commonly a fixed offset applied to a feature boundary, so it can appear as an intercept. A real print can have both effects at once.
Should holes and outside dimensions be calibrated separately?
Yes, when fit matters. Toolpath placement, extrusion width, and slicer compensation can make a hole behave differently from an outside contour. Use two holes together or two outside features together for each calibration run.
Should X, Y, and Z use different corrections?
Often they should be checked separately. Belt motion, skew, cooling, layer height, and first-layer behavior can affect axes differently. Independent-axis scaling is only appropriate where the CAD or slicer workflow supports it and should be verified with a print.
Where should I enter the correction in a slicer or CAD program?
Use whole-model or axis-specific scaling when the result is mainly proportional. Use a slicer contour or hole compensation setting, or a CAD feature offset, when a fixed bias remains. The exact setting names and how they combine vary by slicer, so test on a copy of the profile first.