The vet will have scales so it can be weighed correctly. The ways suggested below can give you a rough idea but won’t be vary accurate. I have found the other ways can be around 50kgs off give or take :) which is still pretty accurate for a horse
Hi, here you have an article explaining how to do the measurements and the calculation : https://practicalhorsemanmag.com/health-archive/weight_calculator_052808
Hope it helped !
Hello Levis, you can estimate a horse's weight by using body measurements like the body length and the heart girth measurement, then you will find some website that will calculate for you :)