Frequency to Wavelength Converter
Calculate wavelength from frequency using λ = v / f. Pick from 19 media (air at multiple temperatures, water, steel, helium, glass, EM in vacuum / water / fibre), output in metres, cm, inches, feet. Includes quarter-wave and half-wave for antenna and standing-wave work.
Input
Result
Wave Speed in Common Media
| Medium | Speed (m/s) | Notes |
|---|---|---|
| Rubber (soft) | ~60 | Highly variable; depends on durometer |
| Air at 0°C | 331.4 | Standard reference temperature |
| Air at 20°C | 343 | Room temperature, dry air |
| Air at 40°C | 355.4 | Hot summer day |
| Helium gas (20°C) | 1,007 | Why helium voice is high-pitched |
| Water (fresh, 20°C) | 1,481 | Pure water at room temperature |
| Seawater (20°C) | ~1,500 | ~3.5% salinity baseline |
| Lead | 1,960 | Dense but slow due to low Young's modulus |
| Concrete | 3,700 | Varies with mix; ~3,200–4,100 m/s typical |
| Wood (oak, along grain) | ~4,000 | Across grain ~1,400 m/s |
| Glass | 5,640 | Longitudinal in standard borosilicate |
| Steel (longitudinal) | 5,960 | One of the fastest common materials |
| Aluminum | 6,320 | Light + stiff = fast sound |
| EM in vacuum / air | 299,792,458 | Speed of light (c) |
| EM in water (n = 1.33) | 225,407,862 | c / 1.33 |
| EM in glass (n = 1.5) | 199,861,639 | c / 1.5 |
| EM in optical fibre (n ≈ 1.47) | 203,939,086 | c / 1.47, typical SMF |
About Wavelength & Wave Speed
Wavelength (λ) is the distance over which a wave's shape repeats: from one peak to the next, or from one zero-crossing to the next of the same sign. It's calculated as λ = v / f, where v is the wave's speed in the medium and f is its frequency. Two waves with the same frequency can have very different wavelengths if their wave speeds differ.
Sound in different media
Sound travels faster in denser, stiffer materials. Air (343 m/s at 20°C) is slow; water is over 4× faster (1,481 m/s); steel is 17× faster (5,960 m/s). A 1 kHz tone has a wavelength of 34.3 cm in air, 1.48 m in water, and 5.96 m in steel. This is why submarines use low frequencies for sonar (longer wavelengths = better penetration), and why ultrasonic sensors for thickness gauging use high frequencies in metals (millimetre-scale wavelengths = millimetre-scale resolution).
Air temperature effects sound speed
Sound in air gets faster as temperature rises. A practical linear approximation is v = 331.4 + 0.6 × T(°C) — at 0°C, sound moves at 331.4 m/s; at 30°C it's about 349.4 m/s. A more accurate physical formula uses absolute temperature: v = 331.3 × √(1 + T/273.15). The two agree within ~1 m/s across the 0–40°C range.
EM waves use a different constant
Radio, microwave, infrared, light, and UV are all electromagnetic waves with speed v = c/n, where c = 299,792,458 m/s and n is the refractive index of the medium (1 in vacuum, ~1.33 in water, ~1.5 in glass). This is over a million times faster than sound, so EM wavelengths are correspondingly much smaller at the same frequency. A 1 kHz EM wave is 300 km long (sub-audio band); a 100 MHz FM signal is 3 m; a 2.4 GHz WiFi signal is 12.5 cm.