Ski sidecut radius calculator

Put in the tip, waist and tail widths and the length of a ski and the calculator above gives you its sidecut radius, then the radius it carves at 30°, 45° and 60° of edge angle. This page explains what the number means and where it stops being true.

The sidecut is the curve cut into the side of the ski, narrower at the waist than at the tip and tail. Measure how much narrower and you have the depth of that curve on one edge. A longer ski with the same depth makes a gentler arc; a deeper cut on the same length makes a tighter one. The radius follows from two measurements, the length of edge between the widest points and the depth of the curve across it. For 122/72/104 mm at 172 cm, the depth is 20.5 mm, the edge between the widest points is 152 cm, and the radius comes out at about 14 m.

That is the nominal geometric radius. It treats the sidecut as one circular arc and assumes the widest points sit 10 cm in from each end, so it will not match the number a maker prints. Makers measure the real shape, which is not a perfect arc. It can read 20 to 40% high on rockered skis, where less of the edge touches the snow. Use it to compare skis and see how width and length change the answer, and if the ski prints its radius, type that into the calculator: the carved radii then use the printed figure, with the geometric estimate beside it.

Radius only tells you what the ski does when it carves flat on its side. You do not ski it flat. Tip the ski onto an edge and it turns tighter, and the further you tip it the tighter it gets. At 30° a 14 m ski carves about 12 m. At 45°, about 10 m. At 60° the radius is exactly halved, so it carves 7 m.

Slide the edge angle above to see it on a carver. There is a price. To balance a tighter carve your body has to lean further and you need to be going faster. The lab says about 26 km/h at 30°, with your body leaning 23° from vertical, and about 33 km/h at 60°, with it leaning 50°. That is the model, with one clean arc and no skidding. A real ski flexes, skids and sheds speed, so a real turn is looser than the calculator says.

The takeaway: a ski’s radius is a starting point, and your edge angle moves it more than most of the gap between two skis does.