How Do You Convert Mach to FPS?
Multiply the Mach number by 1,125.33 to get feet per second at sea level. The formula is: FPS = Mach x 1,125.33. Since 343 m/s x 3.28084 ft/m = 1,125.33 fps, this converts the speed of sound from metric to imperial units.
Tom Brewer compares aircraft and projectile speeds for Maya. A fighter jet at Mach 1.6 flies at 1.6 x 1,125.33 = 1,800.5 fps. A rifle bullet at 2,800 fps = Mach 2.49. The bullet is actually faster than the jet, though only for the first fraction of a second before air drag slows it down.
Ballistic Speed Reference
| Mach Number | FPS | Example |
|---|---|---|
| Mach 0.30 | 338 fps | Crossbow bolt |
| Mach 0.90 | 1,013 fps | Subsonic ammunition |
| Mach 1.00 | 1,125 fps | Speed of sound |
| Mach 1.07 | 1,204 fps | 9mm handgun |
| Mach 2.59 | 2,915 fps | .50 BMG rifle |
| Mach 2.75 | 3,095 fps | 5.56 NATO rifle |
| Mach 4.40 | 4,951 fps | .220 Swift (fastest commercial) |
| Mach 5.10 | 5,739 fps | Tank sabot round |
Practical Applications
Ammunition Selection
Sam Okafor compares cartridge performance. A .308 Winchester at 2,820 fps = Mach 2.51. A .300 Win Mag at 3,000 fps = Mach 2.67. The 180 fps difference (Mach 0.16) means the .300 Win Mag arrives 0.012 seconds sooner at 500 yards and drops 4 fewer inches, but generates 35% more recoil.
Sonic Boom Prediction
Coach Rivera tracks a space launch. The rocket passes Mach 1 (1,125 fps) about 70 seconds after liftoff at approximately 35,000 feet altitude. The sonic boom reaches the launch viewing area about 100 seconds later. By the time the sound arrives, the rocket is at Mach 4.5 (5,064 fps) and 40 miles downrange.
Wind Tunnel Calibration
Dana Kowalski tours a wind tunnel facility. The subsonic tunnel maxes out at 800 fps = Mach 0.71. The transonic tunnel reaches 1,350 fps = Mach 1.20. The supersonic tunnel can hit 4,500 fps = Mach 4.0. Each tunnel uses different measurement equipment: pressure probes for subsonic, Schlieren photography for supersonic flow visualization.