Speed of Sound Calculator

Frequently Asked Questions

How fast does sound travel in air?

About 343 m/s at 20°C. It varies with temperature: v ≈ 331.3·√(1 + T/273.15) m/s, so roughly +0.6 m/s per °C. It is ~1482 m/s in water and ~5960 m/s in steel.

Does humidity or pressure change it?

Temperature dominates. Humidity raises it slightly (humid air is less dense); pressure has almost no effect because density and stiffness change together.

What is Mach number?

Speed divided by the local speed of sound. Mach 1 is the sound speed; above it is supersonic. The tool computes Mach for a given speed and temperature.

How do I find distance from a sound delay?

Distance = speed × time. The classic lightning rule: count seconds to thunder and divide by ~3 for kilometres (or 5 for miles).

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How This Calculator Works

The speed of sound is how fast a pressure wave propagates through a medium, and it depends almost entirely on that medium's stiffness and density - not on the loudness or pitch of the sound. In dry air the dominant variable is temperature, and a tight approximation is v ≈ 331.3 · √(1 + T÷273.15) metres per second, with T in degrees Celsius. The 331.3 m÷s is the speed at 0°C; the square-root term scales it by the ratio of absolute temperatures, because in an ideal gas sound speed goes as √T. For solids and liquids the calculator uses fixed reference values, since sound travels far faster through stiff, dense materials - about 1482 m÷s in water and 5960 m÷s in steel. Results are converted to m÷s, ft÷s, mph, and km÷h, and optionally give the travel time over a distance (t = d÷v) and the Mach number of an entered speed (Mach = speed ÷ v).

Worked Example: A Thunderclap at 20°C

At 20°C, v = 331.3 × √(1 + 20÷273.15) = 331.3 × √1.0732 = 331.3 × 1.0359 ≈ 343.2 m÷s (about 1126 ft÷s or 768 mph). You see lightning, then count 5 seconds to the thunder: distance = v × t = 343.2 × 5 ≈ 1716 m, roughly 1.1 miles - the familiar "five seconds per mile" rule. If a jet flies at 420 m÷s in that same air, its Mach number is 420 ÷ 343.2 ≈ 1.22, meaning it is supersonic and trailing a shock cone.

Where This Is Used

Aviation: Mach number governs aircraft design; the "sound barrier" is Mach 1, and it shifts with altitude because air temperature falls with height.

Audio & acoustics: loudspeaker delay alignment, concert-hall reverberation, and microphone array timing all use v in air.

Ranging: sonar (water), ultrasonic distance sensors, and seismic surveying all infer distance from echo travel time.

Everyday: the lightning-thunder gap, echo timing in canyons, and the crack of a whip (its tip breaks the sound barrier).

Common Mistakes & Edge Cases

Assuming a single fixed "343 m÷s" - that holds only near 20°C; at −40°C aloft it drops to about 306 m÷s.

Thinking louder or higher-pitched sound travels faster - amplitude and frequency do not change propagation speed in a given medium.

Forgetting medium matters most: sound is ~4.3× faster in water and ~17× faster in steel than in air.

Using Celsius directly in a √T law without the +273.15 - the ratio must use absolute (Kelvin) temperature.

Humidity and altitude have small effects this air formula ignores; it is a dry-air approximation good to within ~1 m÷s for normal conditions.

Related Concepts & Limits

The rigorous gas relation is v = √(γRT÷M), where γ is the heat-capacity ratio, R the gas constant, and M the molar mass; the simple √(1+T÷273.15) form is a linearised, dry-air special case of it. In solids the governing equation is v = √(E÷ρ) with E the elastic (Young's) modulus and ρ density, which is why this tool uses tabulated material speeds rather than a temperature formula for them. Sound speed sets the wavelength via λ = v÷f, links to the Doppler effect, and underlies Mach-number aerodynamics. The solid÷liquid values shown are typical references; real speeds vary with alloy, salinity, pressure, and temperature, so treat them as nominal rather than exact.

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