Convert Mach and knots using sea-level, ISA-altitude, or custom-temperature speed of sound, with m/s, km/h, mph, and flight regime.

True airspeed relative to dry air; wind is excluded. Sea-level mode assumes 15°C. Constant-property ideal-gas estimate.

Related Calculators

Mach to Kts Formula

The following formula converts a Mach number M to knots at temperature T (Kelvin) using the ideal-gas speed of sound.

kt = M × √(γ R T) / (1852 / 3600)
  • γ (dry air) = 1.4
  • R (dry air) ≈ 287.05287 J/(kg·K)
  • 1 kt = 1852/3600 m/s exactly (approximately 0.5144444444 m/s)
  • ISA sea level: T = 288.15 K → a ≈ 340.294 m/s ≈ 661.479 kt

Mach to Kts Conversion Table

Mach to Knots (ISA Sea Level, 15°C)
Mach Knots (kt)
0.166.148
0.2132.296
0.3198.444
0.4264.591
0.5330.739
0.6396.887
0.7463.035
0.8529.183
0.9595.331
1.0661.479
1.1727.626
1.2793.774
1.3859.922
1.4926.070
1.5992.218
1.61058.366
1.71124.514
1.81190.661
1.91256.809
2.01322.957
* Values assume ISA sea level (T = 288.15 K), where a ≈ 661.479 kt.

How do you convert Mach to knots? Choose a temperature model (e.g., ISA sea level), compute the speed of sound a = √(γRT), then kt = Mach × a (m/s) ÷ (1852/3600).

How do you convert knots to Mach? Convert knots to m/s (×1852/3600), then Mach = [speed (m/s)] ÷ a where a = √(γRT) at the chosen temperature.

Example Problem

Convert Mach 0.85 to knots at ISA sea level.

Use a ≈ 661.479 kt at T = 288.15 K, then kt = 0.85 × 661.479.

kt ≈ 562.257 kt