A spiral is already drawn. Pick the kind, the number of turns, the weight of the line and which way it winds, and download it as one SVG path sized in millimetres, or as a PNG.

Free, no account. The file is read by code running in your browser. It is not uploaded, and nothing about it is stored.

How to make a spiral

The page opens with an even spiral of five turns. If that is what you came for, download it.
Press another kind to change it: logarithmic, golden, Fibonacci, hypnotic or double. The picture changes at once.
Pick the number of turns, the line (thin, medium or bold) and whether it winds outwards clockwise or anticlockwise.
Open Fine-tune to type an exact size, a number of turns such as 3.5, a line width or a colour.
Download the SVG, or press “Download PNG” for a picture with a see-through background.

The six kinds this spiral maker draws

Even (Archimedean). The distance from the middle grows by the same amount with every turn: r = b × θ. Its coils are evenly spaced, like a rolled-up mat or the groove of a record. Five turns in a spiral 100 mm across lie 10.52 mm apart.
Logarithmic. The distance from the middle is multiplied by the same amount with every turn: r = a × e^(b × θ). Choose 1.5, 2 or 3 times wider each turn. The coils open out faster and faster, and the curve crosses every straight line from its middle at one fixed angle, which is why it is also called the equiangular spiral.
Golden. The logarithmic spiral that gets wider by the golden ratio, about 1.618, every quarter turn. The golden ratio spiral page explains it.
Fibonacci. Quarter circles drawn in squares whose sides are the Fibonacci numbers 1, 1, 2, 3, 5, 8, 13, 21. Eight squares fill a rectangle 34 by 21. It looks like the golden spiral and is a different curve.
Hypnotic. A filled shape, not a line: the band between an even spiral and the same spiral turned half way round, trimmed to a disc. The black band and the white gap are the same width all the way in, and black covers exactly half the disc.
Double. Two even spirals, the second turned half way round the first, joined at the middle into one line that passes through it in a shallow S.

What is in the file

The spiral is a single <path>. The even, logarithmic, golden and double kinds are written as cubic Bézier curves, 32 to each turn, placed so that at every joint the path has both the position and the direction of the true curve. On a spiral 100 mm across the path stays within a hundredth of a millimetre of its equation everywhere. The Fibonacci spiral needs no approximation: its quarter circles are written as true circular arcs.

The size you set is the longer side of the box round that path, in millimetres, and the other side is shown beside the result: an even spiral of five turns set to 100 mm is 100 × 94.77 mm. The page of the file is that box plus half the line’s width all round, so the ink exactly fills it. The width, height and viewBox are in millimetres.

Every kind but the hypnotic one is a line with a stroke width and round ends, not an outlined shape. A pen plotter draws it in one pass without lifting the pen, and a laser follows it once. A cutting machine would cut along the line, not round it: to cut a spiral out as a strip, turn the stroke into an outline in your drawing program first, or take a ready-made one from the spiral vector set, which are filled shapes. The hypnotic disc is already a filled, closed shape, and its page is the square its disc sits in, with the middle of the spiral at the middle of the page so that it spins true.

The numbers beside the result

Under the choices the page gives the equation of the very curve it drew, with its numbers in millimetres and radians. For the even spiral of five turns at 100 mm that is r = 1.6748 mm × θ: after one full turn, where θ is 2π, the line is 10.52 mm from the middle.

It also gives the length of the line, which is the figure you need before bending wire, laying rope or LED strip, or quilting a spiral: that same five-turn spiral is 830 mm long, more than eight times its width. More turns in the same size make a longer line: twelve turns come to 1,927 mm.

What it does not draw

Spirals with corners (square or triangular), spirals with three or more arms, spirals made of dots, and lines that swell from thin to thick. The picture does not spin: this is a still file, not an animation. To wind a photograph into a spiral line, use the Spiral style in the Plotcaster editor.

Questions

Which spiral should I choose?

For evenly spaced coils, such as a coaster, a labyrinth, a coil of rope or a record, choose Even. For a shell, a galaxy arm or anything that opens out as it goes, choose Logarithmic. For the diagram with the squares from a maths book, choose Fibonacci. For the black and white disc that seems to pull you in, choose Hypnotic.

How do I get a black and white spiral as a PNG?

Choose Hypnotic, set the turns, and press “Download PNG”. The black band is drawn and the white band is see-through, so it shows as white on a white page; lay it on any other colour and that colour shows through instead. The PNG is drawn at 300 pixels to the inch of the size you set: 1,181 pixels across for 100 mm.

Is the spiral one continuous line?

Yes. Each kind is one path from end to end, so a pen plotter draws it without lifting the pen. The double spiral is one line too: it runs in along one arm, through the middle and out along the other. Only the Fibonacci spiral’s squares, if you leave them drawn, are a second path.

Can I set the gap between the coils?

Not directly, but it follows from two things you can set. In an even spiral the gap is the size divided by a little under twice the number of turns: 100 mm with five turns gives 10.52 mm. Change the size or the turns under Fine-tune and read the new gap in the line under the picture.

Spiral generator