It's interesting to note, therefore the big advantages of running on the inside lane in a race, particularly middle distance running, where races are won by smaller distances than the 5/10,000m. Someone stuck on lane 2 for a bend will run 4 metres further than if they were in lane 1.
Basically you can exclude the straights as we know they are the same, the difference is the bends, which we can treat as a circle. Obviously the circumference of the circle made by lane 1 is 200m. Using pie, we know therefore the diameter is 63.65m. If the lanes are 1.25m apart, we know therefore the diameter of the next circle (Lane 2), is 66.15m, use pie again to get 207.8 for this new circle, and 407.8 for the whole of lane 2.