Why printed holes come out small
FDM printers approximate circles with straight segments and the plastic squishes outward, so holes typically print 0.1–0.3 mm undersize and pegs slightly oversize. Holes printed sideways also sag at the top. The calculator adds clearance on each side of the part:
hole = nominal + 2 × clearance (+ ¼ nozzle if horizontal)
peg = nominal − 2 × clearance
| Fit | Clearance per side | Use for |
|---|---|---|
| Press fit | 0.05 mm | Bearings, magnets, permanent pins |
| Snug / friction | 0.10 mm | Lids, push-on caps |
| Sliding | 0.20 mm | Hinges, sliding parts, bolts through holes |
| Loose / free | 0.30 mm | Print-in-place joints, quick assembly |
These defaults suit a well-calibrated 0.4 mm nozzle. Print a small test pair to dial in your printer — over-extrusion makes everything tighter, so calibrate e-steps and flow first.
FAQ
What tolerance should I use for 3D printed parts?
0.2 mm per side (0.4 mm on the diameter) is a good default for parts that should slide together. Use 0.1 mm for friction fits and 0.3 mm or more for print-in-place.
What size hole for an M3 bolt in a 3D print?
Model about 3.4 mm for a sliding clearance hole. For tapping or threading an M3 screw directly into plastic, model 2.5–2.8 mm.
Why are my 3D printed holes too small?
Polygonal approximation, plastic squish and over-extrusion. Many slicers also have a 'hole horizontal expansion' setting to compensate automatically.
How do I fit a 608 bearing in a 3D print?
A 608 is 22 mm outside. Model a 22.1–22.2 mm hole for a press fit and test — it varies by printer.
Recommended gear
- Digital calipers (150 mm) — Essential for tolerances, flow calibration and checking prints.
- Deburring tool & flush cutters — Clean up holes, edges and supports.
Some links are affiliate links: if you buy through them MeshMath may earn a small commission at no extra cost to you. Picks are generic categories, not paid placements.
Related tools
STL weight & filament calculator
Drop an STL to get grams, metres of filament and cost for PLA, PETG, ABS and more.
3D print cost calculator
Filament, electricity, printer wear, labour, failure rate and markup — what to charge.
3D print time estimator
Drop an STL and estimate print time and energy use from layer height and speed.
Online STL viewer & measure
View any STL in 3D, get exact dimensions and check it fits your printer bed.
STL scale & unit fixer
Find the exact scale % to hit a target size, or fix inch/cm exports.
Filament length ↔ weight converter
Convert metres of filament to grams and back for any material and diameter.
Lithophane generator
Turn a photo into a printable lithophane STL with a live 3D preview.
Resin print cost calculator
Resin volume with supports, bottle cost, power and price per MSLA print.
Infill strength estimator
Compare infill % and pattern against weight and relative strength.
Name keychain generator
Type a name and download a printable keychain STL.
E-steps & flow calibration calculator
Calibrate extruder e-steps and flow rate, with the exact M92 G-code to send.
Temperature tower G-code generator
Add temperature changes by height to any sliced G-code file.
Filament drying temperature & time chart
How hot and how long to dry PLA, PETG, TPU, Nylon and more.
3D print quote generator
Build a printable price quote for customers with parts, labour, tax and shipping.