We may earn a commission from links on this page.
You just finished running a race, but your watch disagrees with the official distance and timing. Which should you trust? While race organizers can screw up their distance or timing, they usually don't. Let's look at how races are measured and why they may disagree with your watch—which happens more often than you might realize.
How races measure your time
Before we compare a watch time to an official race time, we need to know what kind of official race time we're looking at. There are two different numbers you might see from a race: gun time and chip time. They may differ from each other and from your watch. Here's where each comes from:
Chip time
Chip time, also sometimes called net time, is the time from when you personally cross the start line until you personally cross the finish line. This is the time that matters for most of us.
Chips measure your personal start and finish because big races often have a crowd at the start line. If you’re running a big-city marathon, it could be 10 minutes or more of waiting and then slowly moseying forward with the crowd before you are able to cross the start line. In that case, your marathon could have a 4:40:00 gun time and a 4:30:00 chip time.
The “chip” in the name refers to a computer chip that is usually embedded in your racing bib (the numbers you pin to your shirt). The timing system registers a data point whenever you cross a timing mat on the ground. There is a timing mat at the start and another at the end of the race. (Longer races like marathons and half-marathons may also have timing mats at a few checkpoints along the way, such as the halfway point.)
Gun time
Gun time is the time from when the race starts (often signaled by a starting pistol, hence “gun”) until you cross the finish line. This is also sometimes called clock time.
If you are trying to actually win the race, you may need to care about gun time. Sometimes the rules specify that the person who wins the race is the person who crosses the finish line first, regardless of when they crossed the start line. If you are an elite athlete who is in the running to win a big race, you’ll generally work out arrangements with the race organizer to be at the actual start line when the race starts, so that the gun time accurately reflects how long it took you to run the race.
But for the rest of us, gun time doesn’t matter at all. The exception is if you are in a very small local race that doesn’t use chip timing, or that only has one mat at the finish line (no mat at the start). In that case, only a gun time will be reported, and no chip time.
Watch time
Watch time is the name I’m using here for the time you see on your wristwatch, or in your running app after the fact. If you start and end the timer exactly when you cross the start and finish lines, and never pause it in between, in theory, it should be the same as the chip time. All the major brands of running watches and smartwatches do an accurate-enough job in most situations. But you shouldn't trust it too much—let me explain why.
Chip time is the one that counts (for most of us)
As I mentioned above, gun time only matters if there is no chip time, if you’re trying to win an award in a race that uses gun times for awards, or if you’re trying to qualify for the Olympics.
Use the chip time anytime you’re telling someone what you ran, or when you’re keeping track of your personal bests (PBs). (Only use a watch time if you ran a race with no chip time, and even then make sure to use your actual total time between the start and finish lines, no pausing. In that case, you're not trusting the watch over the chip time; you're just using it to estimate a missing chip time.)
Watch time should be the same as chip time if you started and stopped your watch at the start and finish lines. But it’s often not. Some of the reasons your watch time might be wrong:
Your watch auto-pauses. This is a convenient setting on training runs, if you often stop for a water break or to wait to cross a street. Your watch will pause your run when you stop, and resume recording when you move again. But during a race, stops aren’t free! If you stop to spend two minutes in a porta-potty, that’s still part of your race time.
Your app (such as Strava) might report a “moving” time. Same idea as above, but it happens even if your watch recorded the whole thing. For example, on one longish run I did, I remember stopping to tie my shoe. Strava shows this run as taking 1:17:02. But if I scroll down through the numbers it gives, I can also see an elapsed time of 1:17:28. I guess it took me 26 seconds to tie my shoe.
On Strava, you can make your elapsed time show up first by selecting Edit Activity and then changing Type of Run to Race. If I do that on my shoe-tying run, the elapsed time with the extra 26 seconds shows up on that Strava activity.
There is one other reason why your official race result might not make sense, even if it’s a chip time and it’s showing the same as your watch’s elapsed time: Every now and then, a race organizer fucks up.
One time, I was running a 2K race (1.2 miles) and was expecting a finish time somewhere between nine and 10 minutes. My watch registered a number in that range, but I knew it was probably off by a few seconds. When I checked the official results shortly after crossing the finish line, I had a time of 12:29, about three minutes longer than I was expecting! And in this case, I had started near the start line (it was a small, local race), so I couldn’t blame a gun/chip time difference. Turns out the timing service had accidentally added three minutes to everyone’s times. They noticed the error pretty quickly, though, and my official time was soon updated to 9:29. (I got an age group medal that day, and wrote my time on the back, which is why I remember it all these years later.)
So if your official race result is way off, consider speaking to the race organizer. There may have been an error that affects everybody, or they may only have a gun time and not a chip time.
How races measure distance
There’s one other consideration here: not just the time on your watch, but the distance. You may find that your watch’s time was within a few seconds of your chip time, but the distance seems wrong—usually too long. Or if you upload your run to Strava, you may find that the notorious "Strava tax" has been applied, appearing to shave off a bit of distance. (My best 5K in the last few years was recorded on Strava as 4.99 kilometers and thus didn't update my 5K PR. Am I mad? OK, yes.)
The first thing to check is whether the race course was certified. (Most are.) The process of certifying a race course ensures that the course has been measured to be the correct distance. And that distance is nearly guaranteed to be shorter than most runners actually run. So, yes, you will probably run a smidge longer than 3.1 miles in a 5K (3.1 mile) race!
You can read the USATF course certification guidelines here. Of particular interest is this part: "A race course is defined by the shortest possible route that a runner could take and not be disqualified. A given runner might not follow the shortest possible route…[t]he actual path of any given runner is irrelevant. The shortest possible route is a reasonably well-defined and unambiguous route that ensures all runners will run at least the stated race distance." (Emphasis theirs.)
How does one find the shortest possible route? "You might envision the shortest possible route as a string, stretched tightly along the course so that it comes within 30 cm (one foot) of all corners, straight through S-turns, and diagonally between corners when crossing a street. You should measure the course following the same route as that hypothetical string." In addition, there is a 0.1% correction factor added to the measured distance, to ensure “that your course will not be short, even if you make small errors in following the shortest possible route.”
The only time your smartwatch’s distance should make you doubt the course measurement is if your watch thinks you covered a significantly shorter distance than the advertised length of the race. In that case, check your map to see if the GPS route looks like the route you actually ran. If you had poor GPS accuracy, your watch (or phone) might draw a line that cuts a corner that you did not actually cut.
If your map looks correct, but your distance is still short, it’s worth checking with other runners to see if they had a short distance as well. Mistakes in course measurement or signage are rare, but they happen! The San Francisco Marathon accidentally shaved half a mile off its half-marathon course once. If you think your race course was short, contact the race organizer.
What counts as my PB?
Your PB, or personal best, can be whatever you want it to be in your heart. But if you want to brag about your times or compare them with other runners, you'll want to talk about chip time.
This is where the distance issue comes up. Maybe you finished your first 5K in 30:03 chip time, but your watch congratulated you on a 5K PR of 28:59. What gives? Check the distance, and you might see that your total race distance was 3.22 miles, with 28:59 being the time it took you to hit 3.1 (at which point the finish line was in sight, but you weren't actually done with the race). Sorry, but you didn't officially run a sub-30 5K.
This is why we distinguish race PBs from training PBs. The race course's timing is more accurate, and its certified distance is more accurate than your GPS even though the actual route that you personally run may be a bit longer than the certified distance. People tend to hit PBs at races because that's when you're the best prepared for a big effort and you have a crowd cheering you on. But the distance being potentially longer than advertised means that it is more of an accomplishment to run a "5K" race in a certain time than to run exactly five kilometers in that time.
So when another runner asks for your 5K time, they mean a race. You can proudly and accurately cite your chip time—in our example, 30:03. But you could also add: "My best training PB for that distance is 28:59, so I know I'm going to break 30 minutes officially soon." You will. I believe in you.