---
title: "How much clearance to leave in a 3D printed part: lids, pegs, sliders and holders"
description: "Why printed holes come out small, how much gap each fit needs on an FDM printer (0.1 to 1 mm), and a five-minute test that finds your own printer’s number."
canonical: https://speakcad.com/blog/3d-printing-clearance-how-much-gap-to-leave
published: 2026-10-19
updated: 2026-10-19
publisher: SpeakCAD
---

# How much clearance to leave in a 3D printed part: lids, pegs, sliders and holders

> Why printed holes come out small, how much gap each fit needs on an FDM printer (0.1 to 1 mm), and a five-minute test that finds your own printer’s number.

You drew a 30 mm box and a 30 mm lid. The lid does not go on. You drew a 6 mm hole for a 6 mm shaft. The shaft does not go in. Nothing is broken: extruded plastic spreads a little as it is laid down, so every printed hole is a few tenths smaller than drawn and every printed wall a tenth or two thicker. The gap you leave in the model, the clearance, is what turns a drawing into a part that fits.

## Where the plastic goes

- **Holes shrink.** The nozzle lays a bead whose outside edge bulges into the hole: 0.2 to 0.4 mm smaller in diameter on most machines, more on small holes.
- **Outside walls grow.** The same bulge pushes the outer surface out by about 0.1 mm per side.
- **The first layer squashes.** The bottom millimetre of a part flares out (elephant's foot), so a lid that fits the top of a box may jam on its bottom edge.
- **Corners pull in.** Sharp inside corners fill with a little extra plastic; a round peg in a square hole touches the sides before the corners do.

These effects are stable for a given printer, nozzle and material, which is why a clearance that worked once keeps working.

## The clearance table

Per side, for PLA and PETG on a tuned FDM printer. Double it when you want the total gap across a hole.

| What the part must do | Clearance per side | Example |
|---|---|---|
| Hold tight, never move | 0.1 to 0.2 mm | A 6 mm magnet in a 6.2 mm pocket, a bearing in its seat |
| Stay on, come off by hand | 0.2 to 0.3 mm | A lid that stays shut, a knob on a D-shaft |
| Slide freely without wobble | 0.4 to 0.6 mm | A drawer in its frame, a sliding lid |
| Move loosely | 0.8 mm or more | A hinge pin, a hanging hook on a rail |
| Drop in and lift out | 1 mm | A phone in a stand, a remote in a holder, batteries in a tray |

Two fits people ask about most:

- **A lid on a box.** Make the lid's inside 0.3 mm bigger than the box's outside on every side. Add a 0.5 mm chamfer on the lid's inside edge so it finds the box, and keep the box's bottom edge chamfered too against elephant's foot.
- **Something that clicks in.** A tracker, a battery or a board held by a lip wants 0.2 mm around it and a lip 0.6 to 0.8 mm deep, with a 45° lead-in on the lip so the part snaps past.

## Printers differ: measure yours once

Those numbers are averages. Your printer has its own, and the quickest way to find it is a test print, not a spreadsheet. Print a 20 mm cube and a plate with a 10 mm hole. If the cube reads 20.2 mm and the hole 9.7 mm, you know what to add. The [tolerances guide](/guides/tolerances-and-clearances) has the full method and the numbers for threads, bearings and shafts.

SpeakCAD does this with the part itself. [Fit Check](/guides/fit-check-parts-that-fit-first-time) cuts a five-minute test slice from your model around the feature that must fit. You print the slice, try it on the real thing, tap too tight, perfect or too loose, and the clearance your printer needs is saved to your account: every part after that is built with it. For a lid or a bearing seat, that five-minute print is worth more than any table.

## Describing the fit instead of the number

When you type the part into SpeakCAD, say what should happen, not only the size: "a lid that stays on but lifts off by hand", "a 6 mm shaft that must not spin", "a slot the 2 mm steel ruler slides into". The AI applies the clearance from the table, says which it used in its reply, and the dimensions panel shows the final sizes. If the test print is off, quote what you measured ("the lid is 0.3 mm too tight") and the correction is a small change; on a plan, the first 3 small changes of each part are included, and the download after a fix is free.

If you have never measured for a print, [how to measure an object for a 3D printed part](/blog/how-to-measure-an-object-for-a-3d-printed-part) takes ten minutes and saves a reprint.

Shaping a part by hand (a hole, a cut, an added shape, text, rounded corners, a shell, every size typed in millimetres) is free, and so is downloading what you shaped. With the AI, a new part spends 4 credits on a plan with its first 3 small changes free, a design change 3, a small change 2, a quick edit 1; without a plan a new part spends 3. Start with Maker: 50 credits a month for $7.99, cancel anytime.

## Prompts to try

- A box 80 x 50 x 30 mm with 2 mm walls and a lid that stays on but lifts off by hand, chamfer on both mating edges ([open in SpeakCAD](https://app.speakcad.com/signup?next=%2F%3Fprompt%3DA%2520box%252080%2520x%252050%2520x%252030%2520mm%2520with%25202%2520mm%2520walls%2520and%2520a%2520lid%2520that%2520stays%2520on%2520but%2520lifts%2520off%2520by%2520hand%252C%2520chamfer%2520on%2520both%2520mating%2520edges))
- A knob for a 6 mm D-shaft, 30 mm across, the shaft must not spin, 15 mm deep bore ([open in SpeakCAD](https://app.speakcad.com/signup?next=%2F%3Fprompt%3DA%2520knob%2520for%2520a%25206%2520mm%2520D-shaft%252C%252030%2520mm%2520across%252C%2520the%2520shaft%2520must%2520not%2520spin%252C%252015%2520mm%2520deep%2520bore))
- A tray that holds eight AA batteries lying down, drop in and lift out, with a finger notch at each end ([open in SpeakCAD](https://app.speakcad.com/signup?next=%2F%3Fprompt%3DA%2520tray%2520that%2520holds%2520eight%2520AA%2520batteries%2520lying%2520down%252C%2520drop%2520in%2520and%2520lift%2520out%252C%2520with%2520a%2520finger%2520notch%2520at%2520each%2520end))

## FAQ

### How much clearance should I leave between 3D printed parts?

Per side: 0.1 to 0.2 mm for a press fit, 0.2 to 0.3 mm for a lid or a knob that stays on, 0.4 to 0.6 mm for a sliding fit, 0.8 mm or more for a hinge, and about 1 mm for a holder something drops into. Printed holes come out 0.2 to 0.4 mm smaller than drawn, so clearance in the model is what makes the fit.

### Why are my 3D printed holes too small?

The extruded bead bulges into the hole as it is laid, so a hole prints 0.2 to 0.4 mm under its drawn diameter; small holes lose more. Draw the hole larger by that amount, or let SpeakCAD's Fit Check measure your printer's own number with a five-minute test slice.

## About SpeakCAD

SpeakCAD is the most intuitive CAD for 3D printing, made for people who own a 3D printer and need a part that fits something they have: tap a face and type a size to shape it with simple tools, or describe it to the AI, on your phone or computer, and download a print-ready STL, 3MF or G-code sliced for your printer.

SpeakCAD works inside ChatGPT and Claude as a plugin (an MCP server): ask the assistant for a part with its measurements and SpeakCAD's own CAD AI designs it, shows it in 3D in the chat and hands over a print-ready STL, 3MF or G-code sliced for your printer.

- Live demo, no account: https://speakcad.com/demo
- In ChatGPT, Claude and other MCP clients: https://speakcad.com/chatgpt-plugin, https://speakcad.com/claude-connector, https://speakcad.com/mcp-server
- Pricing: https://speakcad.com/pricing
- FAQ: https://speakcad.com/faq
- Site index for AI assistants: https://speakcad.com/llms.txt