3D Printing Tolerance Calculator
Determine the correct printed dimension for mechanical fits in 3D printing. Enter your nominal size, material shrinkage, fit type, and orientation to get a compensated target dimension ready for your slicer.
Last updated: May 2026
About this calculator
When a 3D printer deposits material, it shrinks slightly as it cools, and the print orientation affects dimensional accuracy differently along each axis. This calculator computes the adjusted dimension you should model or slice to, accounting for both effects. The core formula is: adjustedDimension = nominalDimension × (1 + materialShrinkage) + fitClearance × orientationFactor, where fitClearance is the mm offset for your chosen fit tier: 0.1 mm for a press fit, 0.15 mm for a sliding fit, 0.2 mm for a running fit, and 0.3 mm for a loose fit. Material shrinkage is expressed as a decimal (e.g., 0.02 for 2%). The orientation factor scales the fit clearance because parts printed vertically often have better XY accuracy than Z-axis accuracy. By dialing in these values from a calibration print, you can achieve reliable press-fits, sliding fits, and loose clearance fits without manual trial-and-error.
How to use
Suppose you need a 20 mm shaft hole with a loose fit, PLA shrinkage of 1% (0.01), and an orientation factor of 1.0. Step 1 – Enter nominalDimension = 20 mm. Step 2 – Enter materialShrinkage = 0.01. Step 3 – Select fitType = Loose fit (clearance = 0.3 mm). Step 4 – Enter orientationFactor = 1.0. Calculation: 20 × (1 + 0.01) + 0.3 × 1.0 = 20.2 + 0.3 = 20.5 mm. Model your hole at 20.5 mm so the printed result lands close to the 20 mm loose-fit target.
Frequently asked questions
What is the difference between the press, sliding, running, and loose fit tiers in 3D printing tolerance?
Each fit tier adds a different clearance to the nominal dimension before orientation scaling. A press fit (0.1 mm) is nearly flush, so parts must be pressed together for a tight, semi-permanent bond. A sliding fit (0.15 mm) allows manual assembly with light resistance. A running fit (0.2 mm) is loose enough for parts to move against each other, ideal for hinges or rotating shafts. A loose fit (0.3 mm) gives generous play for parts that need to move freely with minimal friction. Choose press or sliding for joints that should stay fixed, and running or loose for joints that need to move.
How does print orientation affect dimensional tolerance in FDM printing?
FDM printers lay down material layer by layer, so accuracy differs between the XY plane (where the nozzle moves) and the Z axis (where layers stack). XY dimensions are generally more accurate because they follow the motion system directly, while Z accuracy depends on layer height settings. Printing a hole vertically (axis along Z) tends to produce a rounder, more accurate bore than printing it horizontally. The orientation factor in this calculator lets you scale the fit offset to match the axis being printed, so you can compensate for whichever direction is less accurate on your specific machine.
Why does material shrinkage matter when calculating 3D print tolerances?
All thermoplastics shrink as they cool from the glass transition temperature to room temperature. PLA shrinks roughly 0.3–1%, ABS can shrink 1–2%, and engineering filaments like Nylon can shrink 2–3% or more. This shrinkage causes printed parts to be slightly smaller than the modeled dimension, which compounds with fit offsets to create gaps or interferences you did not intend. By multiplying the nominal dimension by (1 + shrinkage), the calculator pre-stretches the target so the finished print lands on your intended size. Measuring a calibration cube and dividing the measured size by the modeled size gives you an empirical shrinkage value to enter here.