Why does Mach 1 vary?

The speed of sound depends on air temperature. At sea level and 20°C it is approximately 343 m/s. At 35,000 ft cruising altitude (−56°C) it is about 295 m/s. This tool uses the sea-level 20°C value as a standard reference.

One knot is one nautical mile per hour. A nautical mile is defined as 1,852 metres, which corresponds to one minute of latitude. Knots are used universally in aviation and maritime navigation.

What is ft/min used for?

Feet per minute (fpm) is the standard unit for vertical speed (climb rate/descent rate) in aviation. Typical climb rates for commercial aircraft are 1,500–3,000 fpm.

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How to Convert Speed Units Free — mph, km/h, knots, Mach (2026)

By Rui Barreira · Last updated: 18 June 2026

Speed units vary by context: road speeds use mph or km/h, aviation and maritime use knots, physics uses m/s, and aerospace comparisons often use Mach numbers. This converter handles all of them in a single table — enter a value in any unit and read all others instantly.

How to Use

Enter a speed value in the input field.
Select the source unit from the dropdown (mph, km/h, m/s, knots, ft/s, ft/min, or Mach).
All conversions appear in the table immediately below.

How It Works

Every unit is converted to metres per second (the SI base unit) using a fixed factor. To convert between two non-m/s units, the tool converts to m/s first, then to the target. For example: 60 mph × 0.44704 m/s/mph = 26.82 m/s; 26.82 m/s ÷ 0.514444 = 52.14 knots.

Unit Reference

1 mph = 1.60934 km/h = 0.44704 m/s. 1 knot = 1 nautical mile per hour = 1.852 km/h = 0.514444 m/s. 1 Mach at sea level (20°C) ≈ 343 m/s ≈ 767 mph ≈ 1235 km/h (Mach varies with temperature and altitude). 1 ft/s = 0.3048 m/s.

Frequently Asked Questions

Why does Mach 1 vary?: The speed of sound depends on air temperature (and to a lesser extent, pressure and humidity). At sea level and 20°C it is approximately 343 m/s. At 35,000 ft cruising altitude (−56°C) it is about 295 m/s. This tool uses the sea-level 20°C value as a standard reference.
What is a knot?: One knot is one nautical mile per hour. A nautical mile is defined as 1,852 metres, which corresponds to one minute of latitude. Knots are used universally in aviation and maritime navigation.
What is ft/min used for?: Feet per minute (fpm) is the standard unit for vertical speed (climb rate / descent rate) in aviation. Typical climb rates for commercial aircraft are 1,500–3,000 fpm.
Is this free?: Yes, entirely free with no signup required.

Frequently Asked Questions

Why does Mach 1 vary?: The speed of sound depends on air temperature. At sea level and 20°C it is approximately 343 m/s. At 35,000 ft cruising altitude (−56°C) it is about 295 m/s. This tool uses the sea-level 20°C value as a standard reference.
What is a knot?: One knot is one nautical mile per hour. A nautical mile is defined as 1,852 metres, which corresponds to one minute of latitude. Knots are used universally in aviation and maritime navigation.
What is ft/min used for?: Feet per minute (fpm) is the standard unit for vertical speed (climb rate/descent rate) in aviation. Typical climb rates for commercial aircraft are 1,500–3,000 fpm.