Deutsches Institut für Normung
That's the German institute for standardization. However, DIN setting is commonly understood as the numbered settings on the front and rear of a ski binding. Those settings are determined by a combination of the skier weight or height, their boot sole length (not size) and their skiing type or level. Those settings should be handled by a qualified shop. That said here’s an educational overview. Please have a shop make any changes to your or your racers DIN. And please have the binding release tested every season by a qualified shop.
Each binding manufacturer has their own chart, this is the Marker DIN, as its a standard, the numbers are effectively the same between brands. To determine the DIN for a 70 lbs skier in a 275mm boot, find the weight range in the left column and move across to the right, this is skier code F. Continue across to boot size, the 271-290 column and a 2.25 DIN is listed. This would be the DIN for a type 1 skier. For type 2 skier, move down the 271-290 column by 1, the DIN is 2.75. For a skier type 3, the DIN is down another, to 3.0 DIN. A 3+ skier type is 4 DIN. If our 70 lbs skier is a type 3, they are skier code H with a DIN of 3. In a shop the DIN is set, then tested with calibrated equipment. For this H skier the twist release of the toe piece should release between 27 and 37, same column and either side of the H release value of 31. The heel piece should release between 102-141. If it does, the bindings DIN are accurate with the release force. If its not, the DIN is adjusted to match the release value range of the H skier code.
To recap skier types: Type 1, Type 2, Type 3, and Type 3+ are Recreational types followed by Racer 1, Racer 2, and Racer 3. Absolutely refer to your coach for their advice in DIN setting.
The skier type for recreational skiing is selected by the skier, not the shop. Basically its Type 1- beginner, Type 2 - intermediate, Type 3 - advanced, Type 3+ is expert. Most skiers are a Type 2 skier for DIN setting.
With racing, things change. Do not proceed further with this unless your racer has a competitive license with US Ski & Snowboard. Always consult your coach for any changes in DIN. Again for educational purposes here’s an overview. In racing, angles are created that are not typical for recreational skiing. Rutted, icy courses that are surface hardened are not typical for recreational skiing. Ski collisions with gates are not typical for recreational skiing. All of these are combined, typical, and frequent for ski racing. As such, higher DIN settings are needed at higher levels of competition. If your racer is development team and racing Nastar and local club races, stay in Recreational skier types. Once they have the competitive license and are competing in state and regional qualifiers this skier type changes. After recreational skier type 3+ is Racer 1, Racer 2, and Racer 3. What that looks like for our 70 lbs 275 sole length skier above is as a Racer 1 - a DIN of 5, Racer 2 - DIN 6, Racer 3 - DIN 7. Its trickier to determine differences between racers, so ask your coach. Start low and increase as needed. First year competitive racer stays at Racer 1 until the ski is popping off from gate contact or rough surfaces. Then move to Racer 2. Again stay there until its a problem. Racer 3 is more typical for FIS and higher level racers only when Racer 2 isn’t keeping the ski on. At no point should a binding be set at the max, even if skier type warrants it, do not set a binding at its highest number. Damage to the ski and skier will result. Race specific bindings DIN ranges go to 15, 17, even 21. To that point, using the Racer skier type settings absolutely increases the risk of a ski not releasing when needed. It is a balanced risk, torn ACL from a boot that hits snow without a ski, or a boot top broken leg from a binding that didn’t release.