40-yard dash to mph
Divide 40 yards by your time and you get your average speed. A 4.50 s 40 averages 18.2 mph. Your top speed during that rep was higher, because that average includes the start from zero.
Conversion chart
| 40 time (s) | Average mph | Average m/s | Average km/h |
|---|---|---|---|
| 4.30 | 19.0 | 8.51 | 30.6 |
| 4.40 | 18.6 | 8.31 | 29.9 |
| 4.50 | 18.2 | 8.13 | 29.3 |
| 4.60 | 17.8 | 7.95 | 28.6 |
| 4.70 | 17.4 | 7.78 | 28.0 |
| 4.80 | 17.0 | 7.62 | 27.4 |
| 4.90 | 16.7 | 7.46 | 26.9 |
| 5.00 | 16.4 | 7.32 | 26.3 |
| 5.20 | 15.7 | 7.03 | 25.3 |
| 5.40 | 15.2 | 6.77 | 24.4 |
| 5.60 | 14.6 | 6.53 | 23.5 |
| 5.80 | 14.1 | 6.31 | 22.7 |
| 6.00 | 13.6 | 6.10 | 21.9 |
40 yards = 36.576 m. mph = 81.82 / time in seconds.
Average speed vs top speed
You start a 40 from zero, so the first 10 yards drag the average down. Most of the time in a 40 goes into acceleration. Developing athletes often reach top speed between 30 and 40 m, right around the 40-yard line, and elite sprinters keep accelerating past 50 m. Two players with the same 4.60 can get there differently: one is quick out of the stance and tops out early, the other starts slower and is moving faster at the finish.
The 10-yard split measures the start and a flying 10 at the end measures top speed. Put them side by side and you can tell whether a slow 40 needs start work or top-speed work.
Getting your real top speed
To measure top speed with timing gates, you set a pair 10 yards apart near the end of the run and divide 10 yards by the time between them. The top speed calculator does that division and has tables for flying 10s and flying 30s.
Sprintbrick skips the zone. A receiver behind the start measures how far away your wearable is 100 times a second, which gives the app your speed at every point of the rep. After a 40, you see your 10, 20 and 30-yard splits, your 40 time, your peak speed and where in the run you hit it.