What tolerance should I use for 3D printed parts?

For clearance fits (sliding/rotating parts), add 0.3-0.5mm to holes and subtract 0.1-0.2mm from shafts. For tight fits, use 0.1-0.2mm total clearance. Always print a test piece first as every printer is slightly different.

Why do holes print smaller than designed?

FDM printers extrude circular beads that extend slightly inward when printing circular holes. This typically makes holes 0.1-0.3mm smaller than the CAD dimension. Adding compensation to hole sizes corrects for this.

How does material choice affect tolerances?

Materials with higher shrinkage (ABS, Nylon) need more tolerance compensation than low-shrinkage materials (PLA, TPU). ABS can shrink 0.5-1%, which on a 20mm part is 0.1-0.2mm — significant for precise fits.

What is the difference between clearance, transition and interference fits?

Clearance fit: parts move freely (bearings, pivots). Transition fit: parts push together by hand (alignment pins, snap-in parts). Interference fit: parts need force to assemble (press-fit bearings, permanent joints).

3DPrintCalcs

Tolerance Calculator — Clearance for Mating Parts

Calculate clearance tolerances for parts that need to fit together.

Nominal Size

Target dimension for the fit

Printer Accuracy

Your printer's typical error

Fit Type

Material

How We Calculate This

Tolerance Formulas

Hole size = Nominal + Fit clearance + Printer accuracy + Shrinkage compensation
Shaft size = Nominal + Fit offset - Printer accuracy
Actual clearance = Hole size - Shaft size
Shrinkage comp. = Nominal size x Material shrinkage rate

The calculator adds printer accuracy compensation to holes (which tend to print small) and subtracts it from shafts (which tend to print slightly large). Material shrinkage is applied to the hole to ensure it remains large enough after cooling.

Frequently Asked Questions

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Clearance Calculator

Calculate the gap needed between moving or sliding 3D printed parts.

Wall Gap Calculator

Find the minimum gap between parallel walls that your printer can resolve.

Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.