Speed of Sound Calculator

Thunder delay, sonar timing, and lab acoustics all need the same constant: how fast a pressure wave moves in the medium. In air that number climbs with temperature; in water it is much larger and still temperature-dependent, but there is no single short polynomial everyone agrees on. This page mirrors the usual split—dry air from the ideal-gas form, freshwater from tabulated experimental speeds—so you can match homework and field estimates without hunting conversion factors.

How to Use This Speed of Sound Calculator

• Pick air or water. Use the top card for dry air and the bottom card for freshwater at atmospheric pressure.
• Set temperature units. Air accepts any numeric °C or °F. Water accepts any °C value or a Fahrenheit preset from the chart range.
• Choose speed units. m/s, km/h, mph, ft/s, or knots—same list for both sections.
• Click Calculate. Each section updates independently when you submit that form.

For general motion at everyday speeds, use the Speed Calculator. For electromagnetic waves in vacuum, see the Speed of Light Calculator. Lightning distance from flash-to-bang delay is covered in our lightning timing resources when you already know air speed.

Speed of Sound in Air

Dry air behaves like an ideal gas for most classroom work. The full form is c = √(γRT/M), which collapses to a temperature-only estimate in meters per second:

c_air = 331.3 × √(1 + T/273.15)

Here T is temperature in °C. Pressure and density drop out of the ideal-gas result at fixed temperature; humidity shifts the value slightly, but the effect is small enough that meteorology homework usually ignores it.

Speed of Sound in Water

At 20 °C, freshwater is about 1481 m/s—near 3313 mph or 4859 ft/s—compared with ~343 m/s in air at the same temperature. Seawater adds salinity and depth corrections that need dedicated oceanographic equations; this tool uses freshwater chart values with linear interpolation between standard reference points from 0 °C to 100 °C.

Reference Values at 20 °C

Frequently Asked Questions

How do I calculate the speed of sound in air given temperature?

Convert to °C if needed, compute √(1 + T/273.15), multiply by 331.3, and read m/s. The air section above does those steps and converts to mph or ft/s when you change the speed unit.

How does the speed of sound change with temperature?

It increases as air warms because molecules carry disturbances faster. The square-root term in the formula captures that growth; cold winter air slows thunder delay compared with a hot summer day for the same distance.

What is the speed of sound in water?

At 20 °C freshwater, about 1481 m/s. Pick 20 in the Celsius water field or 68 °F equivalent and Calculate to see other units. Cold water near 40 °F is closer to 4670 ft/s on the same chart scale used here.

Does air pressure matter?

At a given temperature, ideal-gas theory says no—only T drives c in the simplified formula. Real air with moisture deviates slightly; use instrument data when sonar or metrology specs require it.

Disclaimer. RapidRatio is educational—not a substitute for calibrated acoustic instruments, NOAA sonar tables, or engineering sign-off.