How running tangents can shave minutes off your marathon time

Every certified marathon course is measured at 42.195 km, but here’s the catch: it’s measured along the shortest possible route, following the tangents. That means connecting the corners — running the straightest legal line from one turn to the next. If you don’t run those tangents, you’re almost certainly covering more than the marathon distance. And in a race where every second counts, that extra distance can be the difference between breaking three hours and missing it.

Most GPS watches will confirm this. Ask around after any marathon and you’ll hear the same story: “My watch said 42.7 km.” That extra half-kilometre might not sound like much, but at sub-3 pace it equates to about two minutes of running. No training plan builds in spare minutes. You need to claw back every advantage you can, and running tangents is one of the simplest ways to do it.

The science of course measurement backs this up. Governing bodies like World Athletics and USATF certify courses by riding a calibrated bicycle with a Jones counter, measuring the line that cuts every curve as tightly as possible while remaining within the road. They even add a tiny buffer (usually one metre per kilometre) to ensure the course is never short. So the advertised 42.195 km is guaranteed — but only if you run the same line they measured. Drift wide on every bend, weave through crowds, or hug the outside of the road and you’re handing minutes back to the clock.

So how do you actually run better tangents? First, keep your eyes up. Don’t fixate on the few metres ahead of your feet — scan down the road and plot the straightest line you’re allowed to run. Second, don’t be afraid to move across the road if space allows. The shortest route isn’t always the one everyone else is taking, especially in crowded city marathons. Third, make small, controlled adjustments rather than last-second swerves, which waste energy and can upset your rhythm.

Crowds and pacers can complicate things. If you’re sitting on a 3-hour pace group, they’ll often run wide, leaving safety gaps for the pack. Decide whether the comfort of sticking with them is worth the extra distance. On some courses, especially those with lots of turns, choosing the pacers’ line could add several hundred metres. On a windy day, drafting might outweigh the benefit of tangents, but when conditions are calm, the shortest line nearly always wins.

In training, practice awareness. On your long runs, check how your GPS compares to the course markers and see how much extra distance you’re adding. That awareness builds into instinct on race day.

Breaking three hours is about stacking marginal gains. Mileage, nutrition, pacing, mindset — they all matter. But don’t neglect the geometry of the course itself. Run the tangents well, and you’re not just running smarter — you’re giving yourself free time.