What Speed Converter does
Mach 1 is 761.21 mph in this converter, which is the speed of sound at sea level on a standard 15 °C day (340.29 m/s, or 1,225.04 km/h). Set From to Mach (at sea level) and To to Miles per hour (mph), type the Mach number, and the result appears with the same speed in all six units listed below it. The converter also handles kilometres per hour, metres per second, feet per second and knots in any combination: 1 km/h is 0.277778 m/s and 1 knot is 1.150779 mph. Because Mach depends on air temperature, the Mach figures here apply at sea level only; the page explains how to adjust for altitude.
Mach to mph chart at sea level
Mach numbers from subsonic to hypersonic, converted with the sea-level speed of sound of 340.29 m/s.
| Mach | mph | km/h | m/s | Knots |
|---|---|---|---|---|
| 0.5 | 380.60 | 612.52 | 170.145 | 330.74 |
| 0.8 | 608.97 | 980.04 | 272.232 | 529.18 |
| 0.85 | 647.03 | 1,041.29 | 289.2465 | 562.25 |
| 1 | 761.21 | 1,225.04 | 340.29 | 661.47 |
| 1.2 | 913.45 | 1,470.05 | 408.348 | 793.77 |
| 1.5 | 1,141.81 | 1,837.57 | 510.435 | 992.21 |
| 2 | 1,522.41 | 2,450.09 | 680.58 | 1,322.94 |
| 2.2 | 1,674.66 | 2,695.10 | 748.638 | 1,455.24 |
| 3 | 2,283.62 | 3,675.13 | 1,020.87 | 1,984.41 |
| 3.2 | 2,435.86 | 3,920.14 | 1,088.928 | 2,116.71 |
| 5 | 3,806.04 | 6,125.22 | 1,701.45 | 3,307.35 |
| 9.5 | 7,231.47 | 11,637.92 | 3,232.755 | 6,283.97 |
| 10 | 7,612.07 | 12,250.44 | 3,402.9 | 6,614.71 |
| 20 | 15,224.14 | 24,500.88 | 6,805.8 | 13,229.42 |
| 25 | 19,030.18 | 30,626.10 | 8,507.25 | 16,536.77 |
| 100 | 76,120.71 | 122,504.40 | 34,029 | 66,147.08 |
These are sea-level equivalents. An aircraft flying at Mach 0.85 at cruising altitude is moving through the air more slowly than 647 mph, because the air there is colder and sound travels more slowly in it.
mph to Mach chart
Round mph figures expressed as a sea-level Mach number.
| mph | Mach | km/h |
|---|---|---|
| 100 | 0.1314 | 160.93 |
| 500 | 0.6569 | 804.67 |
| 600 | 0.7882 | 965.61 |
| 700 | 0.9196 | 1,126.54 |
| 761.21 | 1 | 1,225.04 |
| 1,000 | 1.3137 | 1,609.34 |
| 1,500 | 1.9706 | 2,414.02 |
| 2,000 | 2.6274 | 3,218.69 |
| 3,000 | 3.9411 | 4,828.03 |
| 17,500 | 22.9898 | 28,163.52 |
Why Mach 1 is 761 mph here and 767 mph elsewhere
A Mach number is a ratio: speed divided by the speed of sound in the surrounding air. The speed of sound is not fixed. It depends almost entirely on air temperature, and falls as the air gets colder.
This converter uses 340.29 m/s, the speed of sound at sea level in the standard atmosphere, where the air is 15 °C. That makes Mach 1 equal to 761.21 mph. Many charts use 343 m/s instead, the speed of sound at 20 °C, which gives 767.27 mph. Both are correct for their stated temperature; they differ by under one percent.
Altitude matters far more. Around airliner cruising height the standard temperature is about -56.5 °C and sound travels at roughly 295 m/s, so Mach 1 there is about 660 mph. To convert a Mach number for a different temperature, multiply it by the local speed of sound in m/s and enter the answer with From set to Metres per second (m/s). Mach 0.85 at 295 m/s is 250.75 m/s, about 561 mph.
km/h to m/s conversion chart
Kilometres per hour divided by 3.6, with miles per hour for comparison.
| km/h | m/s | mph |
|---|---|---|
| 18 | 5 | 11.18 |
| 36 | 10 | 22.37 |
| 36.7 | 10.194 | 22.80 |
| 48 | 13.333 | 29.83 |
| 54 | 15 | 33.55 |
| 60 | 16.667 | 37.28 |
| 72 | 20 | 44.74 |
| 90 | 25 | 55.92 |
| 100 | 27.778 | 62.14 |
| 108 | 30 | 67.11 |
| 120 | 33.333 | 74.56 |
| 213 | 59.167 | 132.35 |
Multiples of 18 km/h give whole numbers of m/s, because 18 ÷ 3.6 = 5.
Speed conversion formulas
mph = Mach × 761.207 Mach = mph ÷ 761.207 m/s = km/h ÷ 3.6 mph = km/h × 0.621371 mph = knots × 1.150779 mph = m/s × 2.236936
Every unit is converted through metres per second. The factors are 1 km/h = 1/3.6 m/s, 1 mph = 0.44704 m/s, 1 ft/s = 0.3048 m/s, 1 knot = 1852/3600 m/s and 1 Mach = 340.29 m/s. The first four are exact by definition; the Mach value is the standard sea-level figure. A useful check: 60 mph is exactly 88 ft/s.
Worked speed conversions
A supersonic speed in Mach
Value 2000, From Miles per hour (mph), To Mach (at sea level)
2.627406 Mach (Rounded: 2.63 Mach)
Wind speed for a physics problem
Value 3.5, From Metres per second (m/s), To Miles per hour (mph)
7.829277 mph (Rounded: 7.83 mph)
The same 3.5 m/s is 12.6 km/h and 6.803456 knots.
Aircraft speed in knots
Value 135, From Knot (kn), To Miles per hour (mph)
155.355225 mph (Rounded: 155.36 mph)
Orbital speed given in km/s
Value 7000, From Metres per second (m/s), To Miles per hour (mph)
15658.554044 mph (Rounded: 15,658.55 mph)
7 km/s was entered as 7,000 m/s because km/s is not in the unit list. The table shows it as 20.57 Mach at sea level.
Using Speed Converter
- 1
Type the speed into Value, for example 2.2.
- 2
Set From to the unit you have, such as Mach (at sea level).
- 3
Set To to the unit you want, such as Miles per hour (mph).
- 4
Read Result. Conversion details shows the factor used, for example 1 Mach = 761.207051 mph.
- 5
Use the Same value in every unit table to read the speed in m/s, km/h, mph, ft/s, knots and Mach at once.