Assuming you’ve read the what kind of ski to buy post, then the size is going to depend on whether you’re buying a slalom (SL), giant slalom (GS) or multi-event ski. Hopefully you’re starting with slalom, and only buying a giant slalom ski as the second pair. If a coach has advised multi-event, then there’s some information here too.
It would be great if all the ski manufacturers agreed on sizing for junior skis, but sadly, junior sizes are all over the map. If you stick with one brand, or one family of brands, you can mostly progress to the next ski they offer and usually that will be a sufficient increase.
So, for example. You start your 60lb, new-to-racing U8 daughter on a 110cm Rossignol multi-event ski (by the way, in ski racing “U” means “under” so a U8 racer is 7 or younger on December 31). Let’s assume she gets pretty good after a few years and does well in her age group. If she were a more casual competitor, the progression to the next size ski might happen later. Her progression might go something like this, if she were racing on Fisher skis only (other brands might vary a cm in either direction):
| U8, 60lb | 100 or 110cm multi-event |
| U10, 70lb | 120 multi or 120cm Slalom |
| U10, 75lb | 120cm or 125cm Slalom |
| U12, 85lb | 130cm Slalom 143cm GS |
| U12, 90lb | 130cm Slalom 143cm GS |
| U14, 95lb | 135cm Slalom 148cm GS |
| U14, 105lb | 140cm Slalom 153cm GS |
| U16, 120lb | 150cm Slalom 168cm GS |
| U16, 125lb | 150cm Slalom 168cm GS |
| U18, 135lb | 150cm Slalom 168cm GS |
| U18, 145lb | 155cm Slalom 175cm GS |
You’ll note that some years she keeps one or both pairs of skis. That will be a consideration based on her size and skill progression, and of course, you’ll have coaches that know her and can advise. Her boots will get bigger and their flex will change, too. There is an assumed binding progression as well, but this isn’t nearly so complicated.