🌊

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

Frequency

Medium

Air Temperature

°C

−90°C20°C60°C

Wave speed in medium: 343 m/s (Air 20°C)

Common Frequency + Medium Pairs

Result

Wavelength (λ = v / f)

—

Metres (m)

—

Centimetres (cm)

—

Inches (in)

—

Feet (ft)

—

Quarter-wave (λ/4)

—

Half-wave (λ/2)

—

Formula

λ = v / f (wavelength = wave speed ÷ frequency)

For sound in air: v = 331.4 + 0.6 × T(°C)

For EM waves: v = c / n (c = 299,792,458 m/s)

—

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

This frequency to wavelength converter — sometimes called a lambda calculator — gives you 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. The formula is λ = v / f, where v is the wave's speed in the medium and f is its frequency. Converting Hz to wavelength is as simple as dividing the wave speed by the frequency value. Two waves with the same frequency can have very different wavelengths if their wave speeds differ — a concept central to acoustics, antenna engineering, and optics alike.

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). The sound wavelength of a 1 kHz tone is 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 diffraction around obstacles), and why ultrasonic non-destructive testing uses frequencies in the MHz range in metals (millimetre-scale wavelengths = millimetre-scale crack resolution). To confirm what frequency a sound is at in the first place, use the online frequency detector.

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. Humidity has a secondary effect: moist air is slightly less dense than dry air, raising the speed by up to ~0.35% at full saturation — small enough to ignore for most audio work but meaningful for precision acoustic metrology.

EM waves use a different constant

Radio, microwave, infrared, visible light, and UV are all electromagnetic waves with phase velocity 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 the EM wavelength is correspondingly much larger at the same frequency. A 1 kHz EM wave is 300 km long (sub-audio band); a 100 MHz FM signal has a radio wavelength of 3 m; a 2.4 GHz WiFi signal is 12.5 cm; a 5G mmWave signal at 28 GHz is about 10.7 mm. The antenna wavelength at any frequency sets the physical length of the radiating element — which is why this converter includes quarter-wave and half-wave outputs. Optical fibre carries infrared light near 1,550 nm — use this converter with THz frequencies to explore that regime. For a comparison of the calculated period of any frequency, see the frequency to period converter.

Frequently Asked Questions

How do I convert frequency to wavelength?

Divide the wave's speed in the medium by the frequency: λ = v / f. For sound in air at 20°C: λ (m) = 343 / f (Hz). For EM in vacuum: λ (m) = 299,792,458 / f (Hz). Example: a 440 Hz musical note in air has λ = 343/440 = 0.78 m. A 100 MHz FM radio signal has λ = 299,792,458 / 100,000,000 = 3 m.

What's the wavelength of audible sound?

In air at 20°C: 20 Hz (sub-bass) = 17.15 m, 100 Hz (bass) = 3.43 m, 1 kHz (mid) = 34.3 cm, 10 kHz (upper) = 3.43 cm, 20 kHz (limit) = 1.72 cm. Sound wavelengths shorten by exactly 10× for each 10× frequency increase.

Why is my voice high-pitched after inhaling helium?

Sound travels ~2.9× faster in helium (1,007 m/s) than in air (343 m/s). Your vocal tract is unchanged, but the resonant frequencies of the cavities scale with wave speed — they shift roughly 3× higher. Your fundamental pitch is set by your vocal folds (which don't change), but the FORMANT frequencies shift, making your voice sound thin and high.

What's the wavelength of WiFi?

WiFi at 2.4 GHz has λ = 299,792,458 / 2,400,000,000 ≈ 12.5 cm. WiFi at 5 GHz: λ ≈ 6 cm. WiFi 6E at 6 GHz: λ ≈ 5 cm. These short wavelengths explain WiFi antenna design — quarter-wave whip antennas at 2.4 GHz are about 3 cm, easily fitting inside laptops.

How does temperature affect sound speed?

Sound in air increases by about 0.6 m/s for each 1°C rise. So a 440 Hz note has wavelength 78 cm at 0°C, 78 cm at 20°C... actually only a tiny difference because the speed change is small. But for ultrasonic distance sensors and acoustic surveying, the ~5% speed change across 0–40°C matters for accuracy.

What's a quarter-wave used for?

Quarter-wavelength (λ/4) is the resonant length for closed-end air columns (e.g., bottles, ear canals) and the optimal length for basic monopole antennas. A 1 kHz tone resonates in a closed tube ~8.6 cm long (λ/4 of 34.3 cm). A 100 MHz FM antenna ~75 cm long. Half-wavelength (λ/2) is the resonance length for both-end-open tubes (flutes) and dipole antennas.

How do I calculate antenna length from frequency?

The standard rule is: a half-wave dipole antenna length (in metres) = 150 / f (MHz), and a quarter-wave monopole length = 75 / f (MHz). These derive directly from λ/2 = v/2f using the speed of light. For example, a 2.4 GHz WiFi dipole should be about 150/2400 = 6.25 cm per element. In practice, a velocity factor of ~0.95 is applied for wire antennas, making the physical element slightly shorter than the free-space formula predicts.

What is the wavelength of visible light?

Visible light spans roughly 380–700 nm (nanometres). Violet light is ~380–450 nm (~789–666 THz), blue is ~450–495 nm, green is ~495–570 nm, yellow is ~570–590 nm, orange is ~590–620 nm, and red is ~620–700 nm (~483 THz). These correspond to extremely high frequencies — enter a value in THz in this converter to explore the optical spectrum. Infrared begins around 700 nm (430 THz) and extends to ~1 mm.

Why does sound wavelength matter for room acoustics and speaker design?

When a sound's wavelength is comparable to a room dimension, standing waves (room modes or resonances) build up, causing bass frequency peaks and nulls at specific positions. A 50 Hz bass note has a wavelength of ~6.9 m — the same order as many room widths. Speaker enclosure ports, bass reflex tuning, and acoustic panel placement all rely on wavelength calculations. Frequencies whose half-wavelength matches an enclosure dimension can cause internal cancellations, which is why subwoofer cabinet dimensions are engineered precisely.

Related Tools

← All Converters