The long-standing guideline is that rider plus tack shouldn't exceed 20%t of the horse's bodyweight, with 15 % considered more comfortable. A pilot study led by Dr Sue Dyson in Newmarket had to stop tests with heavier riders early because previously sound horses showed temporary lameness and pain behaviour. This matters. Two things people get wrong. First, tack adds up faster than you would think once you include the saddle, numnah, boots and your own kit. Second, the limit should be based on your horse's ideal weight, not their current weight. If your horse is 100kg overweight, using that number to justify a heavier load just stacks strain on strain. Ride-A-Weigh gives you the real figures, so you can protect your horse's long-term soundness with confidence rather than hope.