When you want to buy new shoulderstraps, it is advisable not to determine the length
of the instrument, but the length of the person who is going to play the instrument.
For example a child, who will play a 96-120 bass accordion or a diatonic
accordion, needs shorter straps than an adults needs for the same instrument.
If you are unsure of the length, you can take The length of your old straps as a starting point.
Or you can take 2 pieces of rope with the length we show you on this page and fasten
the rope to your instrument
So you can try which length fits best.