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Speed of Sound Calculator
Calculate the speed of sound in air, water, steel, wood, and other materials. This acoustic velocity calculator adjusts for temperature, returns wavelengths for any frequency, and compares media side-by-side.
Medium & Temperature
Hz
Results
Speed of Sound
343.2
m/s
km/h
1235.5
mph
767.3
ft/s
1126.0
Mach 1
1.000
Formula Used
v = 331.4 + 0.6 × T(°C)
v = 331.4 + 0.6 × 20 = 343.4 m/s
Wavelength at 1000 Hz
0.3432 m
34.32 cm | 13.51 in
Speed of Sound in Common Materials
| Medium | Speed (m/s) | Speed (ft/s) | Relative to Air | Notes |
|---|---|---|---|---|
| Air (20°C) | 343 | 1125 | 1× | Temperature-dependent |
| Air (0°C) | 331 | 1086 | 0.97× | Reference condition |
| Helium (20°C) | 965 | 3166 | 2.81× | High γ/M ratio |
| Hydrogen (20°C) | 1270 | 4167 | 3.70× | Lowest molecular mass |
| Fresh Water (20°C) | 1481 | 4859 | 4.32× | Temperature + pressure sensitive |
| Sea Water (20°C) | 1522 | 4993 | 4.43× | Salinity raises speed |
| Concrete | 3100 | 10170 | 9.0× | Varies by mix |
| Wood (oak) | 3850 | 12631 | 11.2× | Along grain |
| Glass | 5640 | 18504 | 16.4× | Compressive wave |
| Aluminum | 6320 | 20735 | 18.4× | Longitudinal wave |
| Steel | 5960 | 19554 | 17.4× | Longitudinal wave |
How to Use the Speed of Sound Calculator
- Select a medium — choose from air, water, metals, or other materials.
- Set temperature — for gases, temperature significantly changes sound speed. Use the slider or type a value. Switch between °C, °F, or K.
- Enter frequency — the tool shows the corresponding wavelength at that frequency in the selected medium.
- Read results — speed appears in m/s, km/h, mph, ft/s, and as a Mach number relative to standard air.
- Copy results — click Copy Result to copy the full summary to your clipboard.
Speed of Sound Formulas Explained
Speed of Sound in Air (Newton-Laplace)
v = √(γ × R × T / M)
γ = adiabatic index (1.4 for air), R = 8.314 J/mol·K, T = temperature in Kelvin, M = molar mass of air (0.02897 kg/mol)
Simplified Linear Approximation (Air)
v ≈ 331.4 + 0.6 × T(°C)
Accurate within ±0.1 m/s for temperatures from −30°C to +50°C. This is the formula used in most acoustic calculations.
Wavelength from Speed and Frequency
λ = v / f
λ = wavelength (meters), v = speed of sound (m/s), f = frequency (Hz). At 20°C and 1000 Hz: λ = 343/1000 = 0.343 m
Speed in Solids (Longitudinal)
v = √(E / ρ)
E = Young's modulus (Pa), ρ = density (kg/m³). Dense, stiff materials transmit sound faster than air by 5–20×.
Why Does Temperature Affect Sound Speed?
Sound travels by transferring kinetic energy between molecules through collisions. At higher temperatures, gas molecules move faster and collide more frequently, transmitting energy more quickly. This is why sound travels faster on a hot day. The acoustic velocity of a gas is therefore a direct function of its thermodynamic temperature, not its pressure — at constant temperature, doubling the pressure leaves sound speed unchanged because both density and bulk modulus rise equally.
The exact relationship: every 1°C increase raises air sound speed by approximately 0.6 m/s. The standard sound speed formula for dry air is v = 331.4 + 0.6 × T(°C), accurate to within 0.1 m/s across the range −30°C to +50°C. At 0°C, sound travels at 331.4 m/s. At 20°C (room temperature), it travels at 343.4 m/s. At 40°C it reaches 355.4 m/s. Humidity has a small but real effect: moist air is slightly less dense than dry air (water vapour is lighter than diatomic nitrogen and oxygen), raising the speed by roughly 0.3–0.5 m/s at 50% relative humidity.
In liquids and solids, the temperature dependence is more complex — water actually slows down above 74°C due to structural changes, while metals typically slow as they expand with heat. The acoustic impedance of a medium (Z = ρ × v, in Pa·s/m or rayl) also changes with temperature, which matters for reflection and transmission calculations at boundaries.
Practical Applications
- Sonar & Underwater Acoustics — submarines and fish finders must account for temperature, salinity, and depth gradients that change sound speed by 10–15%. The ocean's SOFAR channel (Sound Fixing and Ranging) is a minimum-speed layer at around 700–1200 m depth where sound becomes trapped and can propagate thousands of kilometres.
- Ultrasonic Testing (NDT) — defect detection in metals relies on knowing exact sound speed in the material to locate cracks by time-of-flight. For a quick reference wavelength at your test frequency, the wavelength calculator covers fluids, metals, and tissue.
- Echo Distance Measurement — distance = (v × time) / 2. Temperature corrections are critical for accurate ranging; an uncorrected 10°C error in air introduces about 0.9% distance error.
- Room Acoustics — speaker delay alignment in live sound requires knowing the speed so delay lines are set correctly (distance / speed = delay time). The Doppler effect calculator extends this to moving sources and receivers.
- Aviation — Mach number = aircraft speed / local speed of sound (which decreases with altitude as temperature drops). The speed of sound at altitude is lower than at sea level precisely because the ISA temperature lapse rate cools the air; at 11,000 m, temperature stabilises at −56.5°C and sound speed settles at ~295 m/s.
Frequently Asked Questions
What is the speed of sound at room temperature?
At 20°C (68°F), the speed of sound in dry air is approximately 343.2 m/s (1125 ft/s or 767 mph). This is the standard value used in most acoustic engineering calculations. Temperature is the dominant factor — every 1°C raises the speed by 0.6 m/s.
Does sound travel faster in water than in air?
Yes — significantly faster. Sound travels at about 1481 m/s in fresh water at 20°C, roughly 4.3 times faster than in air. The higher bulk modulus (resistance to compression) of water more than compensates for its higher density, yielding a much higher sound speed.
How does altitude affect the speed of sound?
Altitude affects sound speed indirectly through temperature. At sea level (15°C), sound travels at ~340 m/s. At 10,000 m altitude (−50°C), it drops to ~299 m/s. This is why Mach 1 represents a lower absolute speed at cruising altitude than at sea level.
Why does sound travel faster in steel than in air?
Steel has an extremely high Young's modulus (stiffness) of ~200 GPa. Sound speed in solids depends on √(E/ρ), and although steel is dense (7850 kg/m³), its stiffness wins out — giving ~5960 m/s, about 17× faster than air. This is why railroad workers historically put their ear to the track to hear distant trains.
What is the speed of sound in helium and why do voices change?
Sound travels at about 965 m/s in helium at 20°C — nearly 3× faster than in air. When you inhale helium, sound waves in your vocal tract travel faster, raising the resonant frequencies of your mouth and throat cavities. This shifts formant frequencies up, creating the characteristic "chipmunk" voice. Your vocal cord vibration frequency (pitch) barely changes.
How do I calculate the wavelength of sound?
Wavelength (λ) = Speed of sound (v) ÷ Frequency (f). At 20°C in air: a 100 Hz sound has λ = 343/100 = 3.43 m. A 1000 Hz tone: λ = 0.343 m (34.3 cm). A 10,000 Hz tone: λ = 0.0343 m (3.43 cm). Lower frequencies have longer wavelengths, which is why bass sounds diffract around obstacles more easily.
Does humidity affect the speed of sound in air?
Yes, but modestly. Humid air is slightly less dense than dry air because water vapour (molar mass 18 g/mol) displaces heavier nitrogen and oxygen molecules. At 20°C and 50% relative humidity the speed of sound increases by roughly 0.3–0.5 m/s compared to dry air. For most everyday calculations the effect is negligible, but precision sonar, metrology, and speed-of-sound standards do account for humidity. This calculator's "Air (humid, 50% RH)" option includes the correction.
What is the speed of sound used to calculate Mach numbers?
Mach 1 is the local speed of sound at the aircraft's altitude, not a fixed value. Using the International Standard Atmosphere (ISA) model: at sea level (15°C) Mach 1 ≈ 340 m/s (761 mph); at 11,000 m cruise altitude (−56.5°C) Mach 1 ≈ 295 m/s (660 mph). An aircraft flying at 900 km/h at cruise altitude is therefore already around Mach 0.85. This calculator shows the Mach-equivalent of any medium and temperature in the Results panel.
How is the speed of sound related to acoustic impedance?
Acoustic impedance Z = ρ × v, where ρ is the medium's density (kg/m³) and v is the speed of sound (m/s). The unit is the rayl (Pa·s/m). Impedance governs how much sound is reflected vs transmitted at a boundary between two media — a large mismatch means most energy is reflected. Air has Z ≈ 415 rayl, while water is about 1.48 MRayl, which is why only about 0.1% of airborne sound energy enters water directly.