How Accurate Is The 40 Yard Dash At The NFL Combine?

It isn't run on a track in spikes, but on the turf at Lucas Oil Stadium in cleats, with each position group running separately. Still, the test functions as football's most recognizable measure of straight-line speed.

Every year athletes post eye-popping performances that dramatically increase the buzz surrounding them ahead of April's NFL Draft. In 2017, John Ross set the NFL Combine record with a 4.22, which vaulted him into the ninth overall pick by the Cincinnati Bengals.

At the same time, it is common to see NFL scouts, coaches, and general managers timing prospects themselves and trusting their own stopwatch times rather than the official mark published by the combine.

That discrepancy became a talking point again this year.

Potential top-10 pick Carnell Tate, a wide receiver from the Ohio State Buckeyes football, recorded a 4.53 in the 40-yard dash at the combine. The time surprised many observers who expected him to run significantly faster.

While straight-line speed is only one component of a receiver's ability to separate from defensive backs, Tate appeared quicker than a 4.53 based on his play over the past three seasons.

The result quickly sparked discussion on social media, with reports that several teams had him running considerably faster using their own timing.

As Adam Schefter reported on X:

Ohio State WR Carnell Tate, a potential top 10 pick, was timed by several NFL executives and GMs on Saturday with a 40 time in the range of 4.45-4.47 seconds.

Although the combine registers official times, teams always conduct their own timing, and those measurements sometimes differ from the official results.

Why would the biggest stage for the 40-yard dash produce such different times?

To better understand the discrepancy, we spoke with timing expert Cody Branch, Director of Elite Events at PrimeTime Timing. PrimeTime Timing serves as USATF's timing partner and times many of the largest meets in the United States, including the Millrose Games, the USATF Indoor and Outdoor Championships, and the NCAA Cross Country Championships.

Branch explained that one of the largest differences between track timing and the NFL Combine comes from the removal of reaction time.

In track and field, races begin with a starting gun that electronically triggers the timing system. The finish is determined using a line-scan photo finish camera that captures the precise moment an athlete's torso crosses the vertical plane of the finish line. This system is known as Fully Automatic Timing, or FAT.

Reaction time is therefore included as part of the athlete's total performance. At major championships, sensors in the starting blocks measure reaction time, and any athlete reacting quicker than 0.100 seconds is ruled to have false-started.

We saw this at the 2022 World Athletics Championships when Devon Allen was disqualified from the 110-meter hurdles final after registering a reaction time of 0.099 seconds.

Reaction times among elite sprinters can vary significantly. At the World Athletics Championships 100-meter final in Tokyo last year, reaction times ranged from 0.157 seconds for champion Oblique Seville to 0.211 seconds for Kenneth Bednarek, who finished fourth.

Below are the official results from that race. The margins were so tight that if Seville and Bednarek had swapped reaction times, the finishing order would have nearly changed. Seville would still win in 9.81, but Bednarek and Noah Lyles would have been separated by just one hundredth of a second at 9.89 for the bronze medal.

"In track with fully automatic timing the athlete is set to go with a gunshot, and then there's a 0.100-plus reaction time built into the race," Branch said.

He pointed to Usain Bolt's famous 9.59 world record in the 100 meters at the 2009 World Championships as an example.

"When Bolt ran 9.59 his reaction time was 0.146, so in reality he covered the 100 meters in about 9.44 seconds after leaving the blocks," Branch said.

The 40-yard dash works very differently.

Instead of reacting to a starting gun, athletes begin whenever they choose. The clock starts when the athlete's hand leaves the ground, triggered manually by the timing operator.

"Depending on the type of system, you could potentially game it by starting to move without breaking the beam that's being used to trigger the start," Branch said.

To put that difference in perspective, reaction times in elite sprinting typically fall between 0.13 and 0.20 seconds - roughly the same gap between a 4.45 and a 4.52 40-yard dash, the kind of margin that can dramatically affect how a prospect is evaluated.

The combine uses a hybrid timing system provided by Zybek Sports. The finish is measured electronically using timing gates that stop the clock when something breaks an infrared beam.

That creates another difference between football timing and track timing.

Timing gates stop the clock the moment any body part breaks the beam, meaning a hand or arm extended forward can trigger the finish early. In track and field, the line-scan camera determines the exact moment the athlete's torso crosses the finish line, which provides a standardized reference point.

Those differences may seem small, but they can create measurable variation.

Among the 189 athletes who ran the 40-yard dash at this year's combine, including quarterbacks, linebackers, and linemen, 77 of them - or 40.7 percent - ran between 4.40 and 4.60 seconds.

When so many performances fall within such a narrow range, even small differences in timing methods can dramatically change the order of results.

Track and field faced similar challenges decades ago. Before Fully Automatic Timing became standard, races were often hand timed using stopwatches. Because human reaction time introduced variability, governing bodies required hand times to be rounded up to the next tenth of a second and then converted to electronic equivalents.

For example, a hand time of 10.51 in the 100 meters would first be rounded up to 10.6, then converted to an official FAT equivalent of 10.84 by adding 0.24 seconds.

Those adjustments were designed specifically to account for the inconsistency introduced by human timing.

So from a timing perspective, is NFL Combine timing less accurate than track timing?

Branch believes the answer depends on how the results are used.

"Accuracy is relative based on the rules," Branch said. "I'd say combine timing is less consistent and therefore makes it hard to compare two people against each other solely based on time. One person might know how to game the start or the finish which gives them an advantage over the others."

That is one reason teams increasingly rely on additional data sources when evaluating speed.

Modern tracking systems such as NFL Next Gen Stats collect detailed player movement data during games, including top speed and acceleration. That data can often provide a more complete picture of an athlete's true speed than a single 40-yard dash.

Amazon's Thursday Night Football broadcast even features an alternate feed called Prime Vision that displays real-time player tracking and analytics during the game.

Still, the 40-yard dash remains one of the most recognizable measurements in football.

So what would Branch change if he were responsible for timing the NFL Combine?

"I'd try to standardize the timing more," he said.

"The way 40s are currently timed are easy to deploy but have flaws. You could potentially use a camera-based system to detect the first movement instead of relying on when the athlete's hand leaves the turf, and use a line-scan camera to read the finish so you can be certain you're timing the torso crossing the line."

The trade-off, Branch said, is that the results might not appear instantly.

"Times would probably be slightly slower and might not show up immediately the way they do now," he said. "But it would also lead to more consistent timing, which makes it easier to compare athletes across the board."

And that consistency is something track and field solved long ago.

In other words, the most famous sprint in a multi-billion-dollar sport is still timed using a method track abandoned nearly half a century ago.