3D Printing Tolerance & Fit Guide
Achieving accurate dimensions in FDM printing requires understanding your printer's tolerances and compensating in your design. Parts that need to fit together — snap fits, press fits, hinges, and sliding joints — all require specific clearances. This guide provides tested clearance values for common fit types across the most popular filament materials.
Recommended Clearances by Fit Type
| Fit Type | PLA Clearance | PETG Clearance | ABS Clearance | Description |
|---|---|---|---|---|
| Press fit (tight) | 0.0–0.1 mm | 0.05–0.15 mm | 0.05–0.15 mm | Parts forced together, friction holds them; may need heating |
| Snug / interference fit | 0.1–0.15 mm | 0.1–0.2 mm | 0.1–0.2 mm | Firm push fit, removable with effort; battery covers, caps |
| Sliding fit | 0.15–0.25 mm | 0.2–0.3 mm | 0.2–0.3 mm | Parts slide freely but without play; drawer slides, pistons |
| Easy / loose fit | 0.3–0.4 mm | 0.3–0.5 mm | 0.3–0.5 mm | Parts move freely with some play; hinges, loose joints |
| Free rotation | 0.4–0.6 mm | 0.5–0.7 mm | 0.5–0.7 mm | Parts spin freely; print-in-place bearings, wheels on axles |
Clearances are per side (total gap between parts = 2× the listed value). Values assume a well-calibrated printer with 0.4 mm nozzle at 0.2 mm layer height.
Hole Diameter Compensation
Printed holes are almost always smaller than designed due to the inner perimeter being slightly oversized. Compensate by increasing hole diameters in your CAD model:
| Designed Hole Diameter | Typical Print Result | Recommended Oversize | Notes |
|---|---|---|---|
| 2–3 mm | 0.3–0.5 mm undersized | +0.4–0.5 mm | Screw pilot holes, pin holes |
| 4–6 mm | 0.2–0.4 mm undersized | +0.3–0.4 mm | Bolt clearance holes, dowel pins |
| 8–12 mm | 0.2–0.3 mm undersized | +0.2–0.3 mm | Bearing seats, shaft holes |
| 15–25 mm | 0.1–0.3 mm undersized | +0.2–0.3 mm | Larger openings, pipe fittings |
| 30+ mm | 0.1–0.2 mm undersized | +0.1–0.2 mm | Large openings (percentage error decreases) |
XY vs Z Accuracy
| Axis | Typical Accuracy | What Affects It |
|---|---|---|
| X/Y (horizontal) | ±0.1–0.3 mm | Belt tension, stepper resolution, flow rate, nozzle diameter, shrinkage |
| Z (vertical) | ±0.05–0.2 mm | Lead screw pitch, layer height (first layer squish), elephant's foot |
Z accuracy is typically better than XY because it is controlled by a lead screw rather than belts. However, the first few layers often exhibit elephant's foot (a slight bulge at the base) due to first-layer squish. Most slicers have an “elephant foot compensation” setting to counteract this.
Calculate Your Tolerances
Use our tolerance calculator to work out the right clearances for your specific printer and material:
- Tolerance Calculator — calculate the right clearance for your fit type, material, and printer calibration
All values are guidelines based on well-calibrated consumer FDM printers. Your results will depend on printer quality, calibration, filament brand, temperature, and print orientation. Always print a test piece to verify tolerances before committing to a full production run.