Mach to mph converter
Mach to mph means Mach number times the speed of sound: Mach 1 is about 761.2 mph at 59 °F (15 °C). The speed of sound depends on air temperature, which you set here.
Example: Direction: Mach to speed · Mach number 1 · Unit: km/h · Air temperature 15 °C → Result: Mach 1 = 1,225 km/h at 15 °C. Source: NASA Glenn Research Center, Mach Number: ratio of speed to speed of sound; subsonic M < 1, supersonic M > 1, hypersonic M > 5 (read 13.10.2026). Updated: .
How it is calculated
Mach 1 is about 761.2 mph (1225.0 km/h, 340.3 m/s) at 15 °C. The Mach number is the ratio of an object’s speed to the speed of sound (NASA). In air, v = 331.3 m/s · √(1 + T/273.15 °C): 331.3 m/s at 0 °C and about 343 m/s at 20 °C. That is why there is no fixed Mach-to-mph factor; it depends on temperature.
The formula is an approximation for dry air, and the tool accepts −60 to 60 °C. It differs from the ideal-gas formula v = √(γ·R·T/M) (γ = 1.4, M ≈ 0.02896 kg/mol, OpenStax Eq. 17.6) by less than 0.01 % across that range (calculated). The speed of sound calculator uses the same formula and shows the same values. Textbooks often round to 331 m/s and 273 °C, which gives about 0.1 % less (Mach 1 at 15 °C: 760.5 instead of 761.2 mph).
Mach to mph table at 15 °C
| Mach | km/h | m/s | mph |
|---|---|---|---|
| 0.5 | 612.5 | 170.1 | 380.6 |
| 0.8 | 980.0 | 272.2 | 608.9 |
| 1.0 | 1225.0 | 340.3 | 761.2 |
| 2.0 | 2450.0 | 680.6 | 1522.3 |
| 3.0 | 3675.0 | 1020.8 | 2283.5 |
| 5.0 | 6125.0 | 1701.4 | 3805.9 |
Example: 1000 km/h is Mach 0.816 at 15 °C (1000 ÷ 3.6 = 277.8 m/s, divided by 340.3 m/s). Conversely, Mach 2 at 15 °C is about 1522.3 mph.
Speed of sound by temperature
| Temperature in °C | m/s | km/h |
|---|---|---|
| −50 | 299.4 | 1078.0 |
| 0 | 331.3 | 1192.7 |
| 15 | 340.3 | 1225.0 |
| 20 | 343.2 | 1235.6 |
| 30 | 349.0 | 1256.5 |
Subsonic is below Mach 1, supersonic above it, and hypersonic above Mach 5 (NASA); around Mach 1 the flow is called transonic. For the speed of sound alone use the speed of sound calculator; other speed units are handled by the km/h to mph converter.
Frequently asked questions
How many mph is Mach 1?
About 761.2 mph at 15 °C and about 767 mph at 20 °C (the speed of sound in air).
How many mph is Mach 2?
About 1522.3 mph at 15 °C, twice Mach 1.
Why is Mach 1 not always the same speed?
The speed of sound rises with air temperature: 299.4 m/s at −50 °C, 349.0 m/s at 30 °C.
How do I convert mph to Mach?
Convert the speed to m/s (mph × 0.44704) and divide by the speed of sound. 1000 km/h is Mach 0.816 at 15 °C.
Where does hypersonic start?
According to NASA, above Mach 5.
Sources and legal basis
- NASA Glenn Research Center, Mach Number: ratio of speed to speed of sound; subsonic M < 1, supersonic M > 1, hypersonic M > 5 (read 13.10.2026)
- OpenStax University Physics Volume 1, section 17.2, Eq. 17.6: speed of sound in an ideal gas v = √(γRT/M), γ = 1.4 for air; the tool uses the dry-air form 331.3 m/s · √(1 + T/273.15 °C), which agrees with it to better than 0.01 %; the textbook’s rounded Eq. 17.7 (331 m/s, 273 °C) is about 0.1 % lower (read 13.10.2026)
As of: · Editorial policy
Related tools
- Speed of Sound CalculatorSpeed of sound calculator: get the speed of sound in air from the temperature, then the distance from the travel time, such as lightning to thunder or an echo.
- km/h to mph converterConvert km/h (kph) to mph and back: 100 km/h = 62.14 mph, 160 km/h = 99.42 mph, 200 km/h = 124.27 mph. Also m/s and knots, with a full conversion chart.
- Knots to mph and mph to knots converterKnots to mph: multiply by 1.1508, so 10 kn = 11.508 mph. Type knots for mph, km/h and m/s, or go back from mph to knots, with Beaufort and hurricane speeds.
- Fahrenheit to Celsius converterConvert Fahrenheit to Celsius and back: °C = (°F − 32) ÷ 1.8. Also Kelvin, Rankine and Réaumur, with the working shown and a chart of common temperatures.
- Online CalculatorCalculator online, free and instant: type or tap and see the answer as you go – order of operations, brackets, percent, square root, steps and a history list.
- m/s to mph converterm/s to mph: multiply by 2.2369, so 10 m/s = 22.3694 mph. Convert meters per second to miles per hour or back, with km/h, knots and a speed chart.
- Young modulus calculator: stress, strain and elongation of a rodYoung’s modulus calculator: E = (F/A)·(L₀/ΔL) from force, cross-section, length and elongation – or the elongation of steel, aluminium, copper and more.
- Double integral calculatorDouble integral calculator: integrate f(x, y) over rectangles, regions with curved limits or in polar coordinates – result, error estimate, area and average.
- Five Number Summary CalculatorFive number summary calculator: minimum, Q1, median, Q3 and maximum of a data set with four quartile methods, outlier fences and the working shown step by step.