Aerospaceweb.org | Ask Us Mach vs. Altitude Tables (2024)

How fast is Mach 1, Mach 2, Mach 4, Mach 6, Mach 15, Mach 20, etc. at different altitudes?
- question from name withheld

The first table is in the English System and indicates the speed of sound in miles per hour (mph), feet per second (ft/s), and knots (kts) for altitudes from -15,000 ft to 400,000 ft in 5,000 ft increments.

Mach 1 vs. altitude in English Units

The second table is in the Metric System and indicates the speed of sound in kilometers per hour (km/h), meters per second (m/s), and knots (kts) for altitudes from -4,000 m to 122,000 m in 2,000 m increments.

Mach 1 vs. altitude in Metric Units

The tables are also color-coded to correspond to different regions of the atmosphere. These regions are defined by the behavior of the atmospheric temperature and (by extension) the speed of sound as altitude increases. These regions include:

Layers of the atmosphere

The atmosphere is broken down into regions of decreasing temperature (blue), constant temperature (green), and increasing temperature (red). This behavior is further illustrated below for the Troposphere, Tropopause, Stratosphere, Stratopause, Mesosphere, Mesopause, and lower Thermosphere. Above the Thermosphere is the Exosphere, which is well into what is considered to be space.

Variation of temperature through the layers of the atmosphere

The Mach 1 tables are .gif image files that you can download or print for future reference. Furthermore, the tables can be used to determine the speeds associated with multiples of Mach 1. Mach number (M) is a ratio comparing the velocity of a vehicle (V) against the speed of sound (a):

Knowing M and a, we can also rearrange the above equation to the following form to solve for the velocity V:

If you want to know a multiple of the speed of sound at any particular altitude, simply multiply the value of Mach 1 at the altitude of choice by the desired Mach number. For example, Mach 5 at sea level is 5 times the value of Mach 1 at an altitude of 0 ft (0 m):

These tables were created using the 1976 US Standard Atmosphere. Unfortunately, most textbooks and computer programs that provide Standard Atmosphere tables only go up to a height between 200,000 and 295,000 ft (61 to 90 km). Sources that do provide speed of sound values beyond these altitudes are rather contradictory. To extend our tables up to 400,000 ft (122 km), a few known data points were used to linearly interpolate the remaining values. While the Mach 1 values provided for the Thermosphere may not be precise, they should be reasonable approximations. Beyond 400,000 ft (122 km), the air density is so low that the atmosphere essentially ceases to exist and the speed of sound becomes undefined. It is for these reasons that the height of the atmosphere is considered to be about 400,000 ft, or 76 miles (122 km).

You can also verify the results of these tables against our Atmospheric Properties Calculator. Just enter the altitude and speed to see the corresponding Mach number. Conversely, the user can also enter the atmosphere and Mach number to see the resulting true airspeed.
- answer by Jeff Scott, 23 February 2003

Related Topics:

What is the speed of sound? How fast is Mach 1? What is the sound barrier? How fast do you have to go to break the sound barrier? How fast is the speed of sound at ground level? What does the term Mach number mean? What is the speed of an aircraft traveling at Mach 3 at an altitude of 30,000 feet? What is subsonic speed?

Your site and many others list the speed of sound as 761 mph, but an equal number of other sites say 742 mph. Which value is right? Why are they different?

How can I calculate the speed of sound on Mars?

Why do we use knots? I know that was probably imported from the naval arena, but why do they use it? How fast is a knot?

Where does the word "Mach" come from? Is it an abbreviation?

I was on a flight ... when the TV screen showed a speed of well over 700 mph, and the pilot told us that we were being pushed by one of the fastest tail winds he had ever experienced. ... Did I fly faster than the speed of sound?

Read More Articles:

• Current Question of the Week
• Past Question Archive
• Most Popular Questions
• Search the Archive
• Submit a Question