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Wavelength Calculator
This wavelength calculator converts between frequency and wavelength for sound waves, electromagnetic waves, and radio frequencies. Use it as a frequency-to-wavelength converter or a wavelength-to-frequency converter -- enter either value for an instant result.
Wave Parameters
Wave Speed:
343 m/s
Result
Wavelength
0.3432
meters
cm
34.32
mm
343.2
inches
13.51
feet
1.126
Formula
λ = v / f
λ = 343 / 1000 = 0.343 m
Audio Frequency Wavelength Reference (Sound in Air at 20°C)
| Frequency | Wavelength (m) | Wavelength (cm) | Notes |
|---|---|---|---|
| 20 Hz | 17.16 m | 1716 cm | Lowest audible bass |
| 40 Hz | 8.58 m | 858 cm | Sub-bass |
| 80 Hz | 4.29 m | 429 cm | Bass |
| 100 Hz | 3.43 m | 343 cm | Bass/room mode range |
| 440 Hz | 0.780 m | 78.0 cm | Concert A (440 Hz) |
| 1 kHz | 0.343 m | 34.3 cm | Mid-range reference |
| 4 kHz | 0.0858 m | 8.58 cm | Presence/attack range |
| 10 kHz | 0.0343 m | 3.43 cm | High treble |
| 20 kHz | 0.01716 m | 1.72 cm | Upper hearing limit |
Understanding Wavelength and Frequency
Wavelength (λ, lambda) and frequency (f) are inversely related through wave speed (v): λ = v / f. Double the frequency and the wavelength halves. This relationship is fundamental to acoustics, optics, and radio engineering, and it applies equally to sound wavelength, light wavelength, and radio wavelength calculations.
Why Wavelength Matters in Audio
- Room acoustics — standing waves (room modes) occur when the room dimension equals a half-wavelength (or multiple). A 17 m room has a 20 Hz mode. Use the Room Mode Calculator to find which specific frequencies your room dimensions reinforce.
- Speaker placement — bass management, subwoofer placement, and boundary effects all depend on wavelength relative to room dimensions.
- Microphone design — microphone diaphragms should be small relative to the shortest wavelength to avoid interference and off-axis coloration.
- Acoustic treatment — bass traps must be physically thick relative to wavelength: λ/4 depth for a quarter-wave absorber at the target frequency. A trap aimed at 100 Hz needs roughly 86 cm of depth.
Temperature and the Speed of Sound
Wave speed for sound in air is not fixed — it increases approximately 0.6 m/s for every 1°C rise in temperature. At 0°C the speed is about 331 m/s; at 20°C it is 343 m/s; at 35°C it reaches roughly 352 m/s. Because λ = v/f, a hotter room produces slightly longer wavelengths at the same frequency. This shift is small for most audio work but becomes meaningful in precision acoustic measurement and outdoor PA system timing alignment. Use the Speed of Sound Calculator to find the exact propagation speed at any temperature before plugging it into this calculator.
Wavelength vs. Wave Type
The formula λ = v/f applies to all waves, but wave speed varies dramatically by medium and wave type:
- Sound in air: ~343 m/s at 20°C → 1 kHz has λ = 0.343 m
- Sound in water: ~1481 m/s → 1 kHz has λ = 1.481 m (roughly 4× longer than in air)
- Sound in steel: ~5100 m/s → 1 kHz has λ = 5.1 m (used in ultrasonic non-destructive testing)
- Light in vacuum: 3×10⁸ m/s → 500 THz (visible green light) has λ ≈ 600 nm
- FM radio in air: ~3×10⁸ m/s → 100 MHz has λ = 3 m (antenna quarter-wavelength ≈ 75 cm)
- Wi-Fi 2.4 GHz: λ ≈ 12.5 cm; Wi-Fi 5 GHz: λ ≈ 6 cm — shorter wavelengths are more easily blocked by walls
Frequently Asked Questions
What is the wavelength of 440 Hz (concert A)?
At 20°C in air, the wavelength of concert A (440 Hz) is 343.2 / 440 = 0.780 m (78.0 cm or 30.7 inches). In a violin string, the same 440 Hz corresponds to a half-wavelength equal to the string length when it vibrates in its fundamental mode.
How do I convert wavelength to frequency?
Frequency (f) = wave speed (v) ÷ wavelength (λ). For sound in air: f = 343 / λ. For a 1-meter wavelength: f = 343 / 1 = 343 Hz. Switch to Wavelength → Frequency mode above and enter your wavelength value.
What is the wavelength of FM radio waves?
FM radio broadcasts between 87.5–108 MHz. Using λ = c/f with c = 3×10⁸ m/s: at 100 MHz, λ = 3×10⁸ / 10⁸ = 3 meters. This is why FM antennas are roughly 75 cm long (quarter-wavelength dipole).
Why are bass frequencies harder to absorb acoustically?
Low frequencies have long wavelengths. A 100 Hz wave has λ = 3.43 m. Effective absorption requires material thickness of at least λ/4 ≈ 86 cm. That's why effective bass traps are physically large — thin foam panels only work for shorter wavelengths (higher frequencies).
How does temperature affect sound wavelength?
Temperature changes the speed of sound in air — approximately +0.6 m/s per °C. At 0°C the speed is ~331 m/s; at 20°C it is ~343 m/s; at 35°C it is ~352 m/s. Because λ = v/f, a 10°C rise stretches every wavelength by about 1.8%. At 1 kHz this shifts λ from 0.331 m to 0.343 m. For critical acoustic measurement or outdoor PA alignment, always use the temperature-corrected speed of sound rather than assuming 343 m/s.
What wavelength range corresponds to visible light?
Visible light spans roughly 380–700 nm. Violet light is at the short end (~380–450 nm, ~670–790 THz); red light is at the long end (~620–700 nm, ~430–480 THz). Green, the peak sensitivity of the human eye, falls around 555 nm (~540 THz). Select "Light / EM waves (in vacuum)" and enter a frequency in THz (using the MHz field with a value like 540,000,000 MHz equals 540 THz) to calculate the corresponding wavelength.
Why is antenna length related to the wavelength of a radio signal?
A half-wave dipole antenna is cut to exactly half the wavelength of its target frequency — this creates a resonant standing wave in the conductor, maximising energy transfer. A quarter-wave monopole (one arm of a dipole over a ground plane) is half that length. At 100 MHz FM radio (λ = 3 m) the ideal quarter-wave antenna is 75 cm. At 2.4 GHz Wi-Fi (λ ≈ 12.5 cm) the quarter-wave element is about 3.1 cm. This is why compact devices can embed antennas for higher-frequency bands but need external antennas for lower-frequency long-range links.
What is the wavelength of 5G and Wi-Fi signals?
Wi-Fi 2.4 GHz has λ ≈ 12.5 cm; Wi-Fi 5 GHz has λ ≈ 6 cm. 5G mid-band frequencies (3.5 GHz) have λ ≈ 8.6 cm; 5G mmWave at 28 GHz has λ ≈ 1.07 cm. Shorter wavelengths are more easily blocked by walls, furniture, and the human body, which is why 5G mmWave has shorter range and requires line-of-sight. Enter the frequency in GHz using the RF/Microwave wave type to compute these wavelengths directly.