What tolerance can a 3D printing service hold?

A good FDM service holds about plus or minus 0.2 mm on small parts. Long parts drift a bit more, roughly 0.1 to 0.2 percent of the length. If a single dimension is critical, call it out in your order notes so it gets measured before shipping.

How much clearance should I add between 3D printed parts?

Add 0.1 to 0.15 mm per side for a press fit, 0.2 to 0.25 mm for a snug hand fit, and 0.3 to 0.4 mm for a free sliding fit. Clearance is per side, so a hole for a 10 mm pin with a snug fit should be drawn at about 10.4 mm.

Why do holes in 3D prints come out too small?

Holes print 0.1 to 0.4 mm under size because the slicer approximates circles with straight segments that sit inside the true curve, and the plastic swells slightly inward as it cools. Draw holes 0.2 to 0.4 mm bigger than what must pass through them.

How much tolerance do I need for PLA parts that fit together?

For PLA, 0.2 mm of clearance per side gives a snug fit you can assemble by hand. Go up to 0.3 or 0.4 mm if the parts must slide or come apart often. PLA shrinks very little, so these numbers hold up well across part sizes.

Guide

3D printing tolerances: the real FDM numbers, in mm

A 3D printing tolerance is how far a printed dimension can drift from your CAD model. For FDM, plan on about plus or minus 0.2 mm on small parts, plus a little extra drift on long dimensions. That number decides how much clearance you need between parts that fit together. Tolerance is not the same as clearance. Tolerance is the drift. Clearance is the gap you design in so the drift does not matter.

Standard FDM tolerances in mm

A tuned FDM printer holds about plus or minus 0.2 mm on parts that fit in your hand. On longer parts, add roughly 0.1 to 0.2 percent of the length. A 200 mm part can drift 0.2 to 0.4 mm end to end.

The Z axis behaves differently than X and Y. Height lands in steps of the layer height, usually 0.2 mm. A 5.1 mm tall wall prints as 5.0 or 5.2, not 5.1. Round your heights to the layer height when you can.

If one dimension on your part truly matters, tell us in the order notes. We check critical dimensions before parts ship instead of hoping the average holds.

How much tolerance for a tight fit

Two printed parts that must fit together need designed-in clearance. Use 0.1 to 0.15 mm per side for a press fit. Use 0.2 to 0.25 mm for a snug fit you assemble by hand. Use 0.3 to 0.4 mm for a part that slides freely.

Printing both halves yourself? Test with a small coupon first, not the full part. A 20 minute test print saves a 9 hour reprint.

And remember that clearance is per side. A 10 mm pin in a hole with 0.2 mm clearance per side means the hole is 10.4 mm across.

Why holes print smaller than you drew them

Holes in FDM parts almost always come out 0.1 to 0.4 mm under size. The slicer turns your circle into short line segments that sit inside the true curve. Melted plastic also swells inward a touch as it cools.

The fix is simple. Draw the hole 0.2 to 0.4 mm bigger than the pin or screw it must accept. For screws that cut their own threads into plastic, draw the hole at the screw's minor diameter instead.

Vertical holes (printed standing up through the layers) hold rounder shapes than horizontal ones. A horizontal hole sags slightly into a teardrop as it bridges. Orient the part so critical holes stand vertical when you can.

Does material change the tolerance? PLA vs PETG vs ABS

PLA is the most accurate common material. It shrinks very little as it cools, so it holds the drawn size well.

PETG runs close to PLA but can leave fine strings inside holes and slots. ABS shrinks the most, near 1 percent, which pulls large flat parts out of square. That is one reason we suggest PETG over ABS for big flat parts.

Same rule for all three: the material moves the average a little, but your clearance plan matters far more than the material choice.

Check your part before you order

Our instant quote runs a printability check on every upload. It measures your part, flags walls that are too thin, and catches meshes with holes in them. You see the flags next to your price before you pay anything.

Upload your STL, look at the check, and if a fit is critical, say so in the notes. A human reviews every flagged part before it prints.

Quick takeaways

Plan on plus or minus 0.2 mm for FDM parts, plus about 0.1 to 0.2 percent on long dimensions.
Clearance is per side: press fit 0.1 to 0.15 mm, hand fit 0.2 to 0.25 mm, sliding fit 0.3 to 0.4 mm.
Draw holes 0.2 to 0.4 mm oversize because FDM holes always print small.
Round part heights to the 0.2 mm layer height so Z lands where you drew it.
PLA holds size best, ABS shrinks most. Flag critical dimensions in your order notes.

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Common questions

What tolerance can a 3D printing service hold?: A good FDM service holds about plus or minus 0.2 mm on small parts. Long parts drift a bit more, roughly 0.1 to 0.2 percent of the length. If a single dimension is critical, call it out in your order notes so it gets measured before shipping.
How much clearance should I add between 3D printed parts?: Add 0.1 to 0.15 mm per side for a press fit, 0.2 to 0.25 mm for a snug hand fit, and 0.3 to 0.4 mm for a free sliding fit. Clearance is per side, so a hole for a 10 mm pin with a snug fit should be drawn at about 10.4 mm.
Why do holes in 3D prints come out too small?: Holes print 0.1 to 0.4 mm under size because the slicer approximates circles with straight segments that sit inside the true curve, and the plastic swells slightly inward as it cools. Draw holes 0.2 to 0.4 mm bigger than what must pass through them.
How much tolerance do I need for PLA parts that fit together?: For PLA, 0.2 mm of clearance per side gives a snug fit you can assemble by hand. Go up to 0.3 or 0.4 mm if the parts must slide or come apart often. PLA shrinks very little, so these numbers hold up well across part sizes.