The formula
length = height + level adjustment + use adjustment ± weight correction
Where it comes from
The classic rule measures the kit against the body: skis reach the chin on a beginner and the forehead or above on someone advanced; a snowboard, between the chin and the nose. It works, but it is incomplete, because what flexes the kit is not height but weight. Two people of the same height fifteen kilos apart should not ride the same board: the lighter one cannot bend it and the heavier one overpowers it. So here height sets the base and weight corrects it, within a cap so the correction cannot run away. Use matters too: on piste you want shorter and quicker, off piste longer, which floats better in soft snow.
How to work it out by hand
- Start from your height in centimetres
- Take off for level: about ten centimetres if you are starting, nothing if you are confident
- Adjust for use: shorter for piste and park, longer for off-piste
- Correct for weight against the reference weight for your height
What is worth knowing
The size is a range, not a number: within those ten centimetres the choice is personal and depends on the model, because turn radius and stiffness vary a lot between skis of the same length. On a snowboard there is a second figure this page does not calculate and that matters just as much: the width, set by your boot size. A big boot on a narrow board drags in the snow when you get the board on edge.