I know most of you use the Jackson's Ratio, but I found that unless you have the 'perfect shaped' tortoise, it's not very accurate in my opinion as a graph, so there is another formular for working out if your tortoise is under/over weight. I found this on the BCG a few years back:

Take the torts WEIGHT in GRAMS (eg 82g)

Then take their LENGTH in CENTIMETRES (eg 7.5cm)

DIVIDE (/) their WEIGHT by their LENGTH 3 times, eg 82 / 7.5 / 7.5 /7.5 = 0.19

Then using the table below you can work out if they are safe to hibernate;
< 0.16 = Underweight - requires special care - *MONITER WEIGHT CLOSELY*
0.17 - 0.18 = Light for hibernation *MONITER WEIGHT CLOSELY*
0.19 - 0.22 = Ideal weight range, Safe to hibernate
> 0.23 = Overweight - if female could be due to carrying eggs - *MONITER WEIGHT CLOSELY*

Again this is for guidence only. There has been occassion's where mine have come up as 0.16 but I still hibernated as I knew that the tort had been vet checked, was eating & drinking and fully wound down.

For hibernation, I always take the weight at the beginning of wind down then when wind down has been completed. I tend to go with the pre-wind down weight as I feel that provided they are a healthy weight at the start of wind down they should still be fine after!

Don't forget to take into consideration whether they have just eaten, poo'd or had a drink!

For those of you that are too lazy to work it out yourselves please click here:

http://www.tortoise-protection-group.or ... te/171.asp

and it will work it out for you!