How to add dimensions to an STL file

STL Ruler turns a 3D model into a clean 2D image with measurement lines: the picture buyers expect on a product listing. It runs in your browser, so there is nothing to install, no sign-up, and your STL is processed right on your computer.

Add dimensions to an STL in 4 steps

1. Drop your STL file. Drag one or more STL files onto the page, or use Import STL. Binary and ASCII STL both work, and a whole size series (S, M, L, XL) can go in at once.
2. Pick a view. Choose front, back, side, top, bottom or isometric, or click any edge or corner of the view cube. Rotate in 90° steps or by any angle, and duplicate a model to show several views of the same part side by side.
3. Check the dimensions. Width and height appear automatically (plus depth in 3D views) and follow the model as you move or resize it. Drag them into place, change their colour, or add your own point-to-point rulers that snap to corners, edges and centres.
4. Choose units and export. Show millimetres, centimetres, decimal or fractional inches, or mm and inches together. Add labels, line up a series with one click, then export a JPG, free up to 1280 px. Your workspace is still there when you come back.

What people use it for

• Product listings for 3D-printed items on Etsy, eBay, Amazon or your own shop, so buyers see the real size before they order.
• Size charts for a series: every size on one image, lined up and labelled.
• A quick size check of an STL before you print it or quote it.
• Dimensioned drawings for a client or a spec sheet, as SVG or PDF, or DXF at 1:1 scale for CAD (Pro).

Every setting

• Your workspace restores itself. Reload the page and your models, measurements, views and undo history are back (stored in your browser only). Start over (↺) clears the models, text and images and keeps your settings; its dialog can also reset every setting.
• Remembered settings (Pro). Your last used artboard, pattern, units, ruler style and model look come back whenever the app opens on an empty artboard — on any computer.
• Views. The view cube in the right panel's View drawer, or the view buttons, snap Front, Top, Iso… Perspective and rotation are per model.
• Split model. Cuts a model open along X, Y or Z at any position (0–100 %) to show its inside; the cut face is hatched, solid or outlined, and the ruler tool snaps to its corners — ideal for wall thickness. “Add other half” shows the opposite piece.
• Models list. Picks the model to edit on the right; hover a row to find its model on the artboard, drag rows to reorder. The ⧉ button adds another view of the same file.
• Labels. The Model label and View label drawers put each label on any side of the model; Spacing moves it closer or further away.
• Rulers. Drag a ruler by its line or its value. A value too long for its line moves beside it on its own; select the ruler to keep it on the line or beside it, slide it along the line or move it further out.
• Backgrounds. Ruler values, labels and text can each sit on a box — in the artboard colour or one you pick — with padding and opacity. Transparent exports leave the artboard-coloured boxes out and keep the coloured ones.
• Units. mm, cm, decimal or fractional inches, or dual display. Fractional mode rounds up for listings; metric can round up to the next 10 mm.
• Artboard. Etsy, Amazon, Instagram and FHD set the image shape and its exact export size (e.g. Etsy 3000 × 2250; Pro above 1280 px). A4 print and Custom cover everything else. Artboard → Pattern adds a grid, graph paper, dots or an isometric grid that scales with the models, from 1 % opacity up.
• Text. Add Text puts a title on the artboard: several lines, size presets, bold, italic, UPPERCASE or lowercase, colour, letter spacing and alignment. Drag to move, double-click to edit; centre it on the artboard horizontally or vertically. Images centre the same way.
• Arrange. Lay a whole series out in one click — by the Models list order after you reorder it — in one row, 2, 3 or 4 per row or your own rows (e.g. 4 · 3 · 2). Spacing in each row: columns, even gaps, space between or space around; line up the models' tops, middles or bottoms. Shift-click models to pick several: Align and Distribute (equal gaps) then act on just those, and dragging one moves them all. The frame button in the zoom bar outlines the area inside the padding while you arrange.
• Style presets. Save your whole look — ruler style, units, background, pattern, outline, fill and labels — and apply it to every model (saving presets is Pro). Nine built-in looks to start from.
• Saved compositions (Pro). Save composition keeps the layout and its STL files in your cloud storage — each file once — to open again on any computer. Once saved or opened, Update saved composition saves your later changes into it and Save as new composition makes a copy. Drag the saved ones left or right to put them in your order; the open one comes first. When Pro ends they are deleted 14 days later.

Keyboard: Del deletes the selection · Ctrl/⌘ Z undo · Ctrl/⌘ Shift Z redo · R ruler · Esc cancel · Space + drag or middle-mouse drag pans · Ctrl/⌘ + scroll zooms.

Free and Pro

Everything you need for a listing image is free. Pro is for vector files, very large images and saving your work in the cloud, from $10 a month or $100 a year, and you can cancel any time.

Frequently asked questions

Is STL Ruler free?

Yes. Importing STL files, every view, automatic and manual dimensions, all units and JPG exports up to 1280 px are free, with no account needed. Pro adds PNG, SVG, DXF and PDF exports, sizes up to 8K and cloud storage for saved compositions, from $10 a month or $100 a year.

Do I need to install any software?

No. STL Ruler runs in any modern browser with WebGL (Chrome, Edge, Firefox, Safari) on Windows, macOS, Linux and ChromeOS. Open stlruler.com and drop in a file.

Is my STL file uploaded?

Not unless you choose to save it. Your STL file is read and drawn in your browser. It is only uploaded when a Pro user saves a composition to their private cloud storage, and it is deleted with that composition. Pro exports are rendered on the server from the finished 2D drawing only, never from the 3D file.

My STL shows the wrong size. What do I do?

STL files store no units, so STL Ruler reads them as millimetres, which is what most slicers and CAD tools export. If your file was saved in centimetres, metres or inches, choose that unit for the model and it is rescaled to its true size.

Can I show dimensions in inches?

Yes: millimetres, centimetres, decimal inches, fractional inches (1/2 to 1/32) or millimetres and inches together. Fractional inches round up, so a 3.92 inch pot reads 4 inches rather than underselling its size.

Can I measure between two points?

Yes. The ruler tool adds point-to-point dimensions that snap to corners, edge endpoints, midpoints and centres, and they follow the model when you move it.

Can I export dimensions for CAD or print?

With Pro you can export SVG and PDF vector files and DXF at true 1:1 millimetre scale, with separate layers for outlines, hidden lines, dimensions and labels.

How much cloud storage do I get?

Solo 100 MB, Team 200 MB or Agency 500 MB. It counts the STL files and images your saved compositions use, each file once, plus their layouts. You can switch plans from the account menu; the change applies at your next billing date.

How do I cancel?

Open the account menu (the button with your name, top right) and choose Cancel Pro, then click again to confirm. Pro stays until the end of the period you paid for, and you can resume before then. Payments are not refunded.

Start measuring