Calculating weight with length and girth

[Fruitcake]

Does anybody know which points to measure length from when using the girth x girth x length ÷ 11877 method for calculating weight? Is it from the centre of the chest like a rug measurement or from the shoulder? If I had to take a guess, I'd say the shoulder but I'm not sure.

I've measured both and done the claculation with each and, obviously it makes quite a difference to the final weight so just need this clarified.

Thanks

 

[Burnttoast]

Point of shoulder afaik