STEP to DXF converter, free and in your browser

How to convert a STEP file to DXF

1. Drop a STEP or STP file on the box above, or click the box to choose one.
2. Check the sheet. If the front view shows the top of the part, click Y next to UP AXIS, under the sheet, and the views are drawn again.
3. Click Download DXF. To save the same sheet in another format, click Download SVG or Download PDF.

The STEP file is read by the OpenCascade geometry kernel, compiled to WebAssembly, which runs inside this browser tab. The file stays on your computer, and so does the drawing made from it.

What the DXF contains

The DXF holds one drawing sheet with three views of the part: front, top, and right side. The views follow third-angle projection, the North American convention, so the top view sits above the front view and the right side view sits to its right.

• Visible edges on a layer named VISIBLE. These are the edges where two faces meet at an angle, and the outlines of curved surfaces, such as the sides of a shaft.
• Overall dimensions on a layer named DIMENSIONS: the width under the front view, the height beside it, and the depth under the right side view. They are rounded to 0.1 mm, or to the millimetre on parts longer than a metre.
• A border and a title block on a layer named TITLE, with the file name, the units, the scale, the date, and the third-angle projection symbol.

The file is ASCII DXF R12 in millimetres, made of LINE and TEXT entities only. The views are drawn at full size, so a distance that you measure in CAD is the real distance on the part. The border and the text are scaled to match, so the sheet prints on letter paper at the scale in the title block. The PDF is the same sheet on letter paper.

What the drawing leaves out

The sheet is a starting point for a drawing. Before you send it to anyone, check what it does not include:

• Hidden lines. Edges behind other faces are left out, not dashed, so internal features such as cross holes do not appear.
• Feature dimensions. Holes, radii, and positions are not dimensioned. You get the overall size only.
• Tangent edges. Where a fillet blends smoothly into a face, no line is drawn.
• Arcs and circles. Curves are written as chains of short straight lines, so a hole is a many-sided polygon in the DXF.
• Tolerances, notes, section views, and an isometric view.

An assembly is drawn as one shape, with every part in the same three views.

How the views are made

The kernel covers every surface of the model with small triangles. The converter then picks the edges to draw: every edge where two faces meet at more than 10 degrees, plus, in each view, the outline of each curved surface, where the surface turns edge-on to you.

To decide what you can see, the converter renders a depth image of the part for each view, then keeps only the parts of each edge that nothing sits in front of. Lines that land on top of each other, such as the front and back edges of a block, are merged into one.

CAD programs disagree about which axis points up. The converter starts with Z up, and the Y setting covers programs that export with Y up.