In human sporting events the difference between finishing first and second is often less than 1%. For each sporting discipline it is important to know how large an enhancement of performance needs to be before it makes a difference to the medal winning prospects of that athlete. In contrast to the known winning margins in many human sporting disciplines, the winning margins in horse racing are unknown. The winning margins for Group 1, 2 and 3 flat and national hunt races over a 5 year period were calculated. For flat races 3 categories were included: flat races of 6 furlongs, 1 mile or 1 mile 4 furlongs. For national hunt 2 categories were included: hurdle races over 2 miles or chase races over 3 miles. Race times from a total of 416 races were included (275 flat races and 141 national hunt races). Overall the percentage difference between first place and second place was only 0.32%, the difference between coming first and third was 0.75% and between first and fourth was 1.15%. Overall the winning margins between first place and second place were closer for flat races than for national hunt races. When a 1% improvement was applied to the fourth placed horse this would result in the winning time in 76% of flat races and 50% of national hunt races. This study shows the very small margins between winning and placing in horseracing. These results are similar to those of elite human sporting disciplines. This suggests that training strategies and veterinary interventions that result in a small percentage improvement in performance may translate to a meaningful difference in terms of winning/placing.