Hand-timed vs electronic 40-yard dash
Hand-timed 40s come out faster than electronic ones, by about two to three tenths. That's the gap between a good time and a great one, so check which kind you're looking at before you compare.
What the research found
| Study | Athletes | Hand faster by |
|---|---|---|
| Mayhew et al., 2010 | 59 Division II football players | 0.31 s (4.85 vs 5.16) |
| Mann et al., 2015, experienced timers | 81 Division I football players | 0.22 s |
| Mann et al., 2015, novice timers | Same athletes | 0.26 s |
Mayhew's group also found the hand timers disagreed with each other by up to 0.19 s on the same rep. Mann's group put the smallest change worth paying attention to at 0.12 s electronic and 0.14 s by hand, so a tenth of improvement on a stopwatch could be noise.
Why hand times are fast
The person holding the watch reacts to the athlete moving, so the first fraction of a second never makes it onto the clock. At the finish they see the athlete coming and stop the watch early. Both errors push the time down, and experience doesn't fix them: the experienced timers in Mann's study were only 0.04 s closer than the novices.
Converting hand to electronic
For track, the NFHS has coaches round a hand time up to the next tenth and add 0.24 s to estimate an electronic time, and only for seeding. The 40-yard studies above land in the same range, so adding 0.24 s to a hand-timed 40 gets you a fair estimate.
| Hand time | About electronic |
|---|---|
| 4.40 | 4.64 |
| 4.50 | 4.74 |
| 4.60 | 4.84 |
| 4.80 | 5.04 |
| 5.00 | 5.24 |
Hand time + 0.24 s. A rough guide; individual timers vary by more than this.
Getting an electronic time
You need something that starts and stops without a human thumb, such as gates, a laser or a wearable. Sprintbrick starts the clock when the sensor on your lower back has moved 0.5 m, and records every split from there. We're still refining that start. In our latest test against OVR gates, the first 10 m read 0.04 to 0.09 s slower than the gates, while everything after 10 m agreed within 50 ms. Full results.