3D Print Scaling Calculator
Calculate the exact scaling factor to apply in your slicer so a printed part matches a target dimension, accounting for measured shrinkage and a tolerance buffer. Ideal for dialing in first-article prints.
About this calculator
Even a well-calibrated printer produces parts that differ slightly from nominal dimensions due to material shrinkage and thermal effects. This calculator finds the multiplier you need to rescale your model before slicing using the formula: scalingFactor = (targetDimension + toleranceBuffer) / (measuredDimension × (1 − materialShrinkage / 100)). The numerator adds a tolerance buffer to the target — useful when you want a part to be slightly oversize before machining or sanding. The denominator normalizes the measured dimension by backing out the known material shrinkage percentage, effectively estimating what the printer would produce at 1× scale with that material. Dividing the two gives you the factor to enter in your slicer's X, Y, or Z scale field. A result above 1.0 means you are scaling up; below 1.0 means scaling down.
How to use
You need a 30 mm bore, measured a test hole at 29.5 mm, PLA shrinkage is 1% (materialType = 1), and you want a 0.1 mm buffer. Step 1 – Adjusted measured dimension: 29.5 × (1 − 1/100) = 29.5 × 0.99 = 29.205 mm. Step 2 – Numerator: 30 + 0.1 = 30.1 mm. Step 3 – Scaling factor: 30.1 / 29.205 = 1.0306. Enter 103.06% in your slicer's scale dialog for the relevant axis. The next print should land much closer to your 30 mm target with the 0.1 mm buffer built in.
Frequently asked questions
How do I find the material shrinkage percentage for my filament?
The most reliable method is empirical: print a calibration object (typically a 20–50 mm cube) with no scaling, let it cool fully, measure it with calipers, and compute shrinkage as (modeledSize − measuredSize) / modeledSize × 100. This gives you the actual shrinkage for your specific filament brand, nozzle temperature, and cooling settings — all of which affect the result. Published shrinkage values from manufacturers are a useful starting point (PLA ~0.3–1%, ABS ~1–2%, Nylon ~2–3%), but empirical measurement is always more accurate for precision work.
Should I apply the scaling factor to all three axes or just one axis in my slicer?
It depends on whether your dimensional error is uniform or axis-specific. If your calibration cube is uniformly undersized in X, Y, and Z by the same percentage, apply the same scaling factor to all three axes. However, FDM printers often have different errors per axis — Z accuracy depends on layer height and lead screw pitch, while XY accuracy depends on belt tension and stepper calibration. Measure all three axes of your calibration cube separately, compute an individual scaling factor for each, and apply them independently in your slicer's per-axis scale settings for best results.
What is a tolerance buffer and when should I add one in 3D print scaling?
A tolerance buffer is a small positive or negative offset added to the target dimension before computing the scaling factor. A positive buffer makes the printed feature slightly larger than nominal — useful for holes or bores that will be reamed, tapped, or sanded to final size. A negative buffer makes features slightly smaller, useful for shafts that need to press-fit into a tight bore. For most snap-fit or slip-fit applications a buffer of 0.1–0.3 mm is typical. If you want an exact nominal dimension with no intentional offset, simply set the tolerance buffer to 0 mm and the formula reduces to a straight shrinkage correction.