Four modes, one panel.
Pick a tab below — everything recalculates live as you type, and every result explains itself.
Switching targets keeps your numbers — the panel simply solves for the third quantity.
The length of one full cycle — crest to crest, or compression to compression.
Cycles per second — 440 Hz is the concert A that orchestras tune to.
Light ≈ 299,792,458 m/s · sound in air ≈ 343 m/s · sound in water ≈ 1,481 m/s.
The wave’s length in empty space — “550 nm light” means exactly this. Inside a material it shortens to λ ÷ n.
Only speed and wavelength change with the medium — frequency and photon energy never do.
Cycles per second — 440 Hz is the note most instruments tune to.
Sound races through liquids and metals far faster than through air.
Speed rises with temperature — 331 m/s at 0 °C, about 343 m/s at 20 °C.
How hard the string is stretched. Guitar strings sit near 60–80 N; piano strings can top 700 N.
Mass per metre of string. A steel guitar high E ≈ 0.4 g/m; a wound bass E ≈ 35 g/m.
The note the string plays — its fundamental frequency.
Four steps, ten seconds.
No manual needed — pick a mode, type two numbers, and read your answer with the working shown.
Pick your wave
Choose the tab that matches your problem — a general wave, light, sound in a material, or a wave travelling along a stretched string.
Enter what you know
Any two of wavelength, frequency and speed — or a photon energy for light. Set units from the small dropdowns, or tap an example chip to load everything at once.
Read the live answer
The big number is your result. The rows beneath add period, wavenumber and unit conversions — plus the EM band for light and the nearest musical note for sound.
Trust the working
Every answer shows its formula with your numbers substituted — perfect for homework. One tap on COPY takes the whole summary with you.
Every formula it uses.
Nothing hidden — these six relations power every number on this page.
The wavelength formula
Wave speed divided by frequency — the distance one full cycle covers. 343 m/s at 440 Hz gives the 0.78 m concert A.
Frequency
The same triangle rearranged: how many cycles pass a point each second when you already know the spacing and the speed.
Period & wavenumber
Period is seconds per cycle; wavenumber is radians per metre — the wave’s frequency written in space instead of time.
Photon energy
h = 6.626×10−34 J·s and c = 2.998×108 m/s. Visible light spans about 1.6–3.3 eV, and λ(nm) × E(eV) ≈ 1240.
Speed of sound in air
T is the Celsius temperature — at 20 °C this gives 343.2 m/s. The shortcut v ≈ 331.3 + 0.606·T stays close near room temperature.
Wave on a string
Tension F over linear density µ, square-rooted. Combine with λ = v ÷ f to find the wavelength of the note the string sounds.
Wavelength, decoded.
The questions students actually ask about λ — answered in plain language, with the numbers to back them up.
Something not adding up? Send us the numbers and we’ll help you work it through.
CONTACT USWhat is the formula for wavelength?+
Divide the wave’s speed by its frequency: λ = v ÷ f. A 440 Hz sound wave moving at 343 m/s has a wavelength of 343 ÷ 440 ≈ 0.78 m.
Keep speed in m/s and frequency in Hz and the wavelength comes out in metres — the same triangle also gives f = v ÷ λ and v = λ × f.
How do I calculate the wavelength of a sound wave?+
Take the speed of sound in the medium and divide by the frequency. In air the speed depends on temperature — about 331 m/s at 0 °C and 343 m/s at 20 °C — so a 440 Hz concert A stretches about 0.78 m from compression to compression.
The Sound waves tab computes the speed from your air temperature, or uses preset speeds for water, glass, steel and aluminium.
How do I calculate the wavelength of light?+
Use the speed of light, c = 299,792,458 m/s. Green 532 nm laser light has a frequency of f = c ÷ λ ≈ 563 THz, and each of its photons carries E = hc ÷ λ ≈ 2.33 eV.
The Light & photons tab converts between wavelength, frequency and photon energy in a single step, and names the EM band the value falls in.
Does wavelength change when a wave enters a new medium?+
Yes — but frequency never changes. When light passes from air into water it slows to c ÷ 1.33, so its wavelength shrinks by the same factor: 532 nm green light becomes about 399 nm inside water.
The colour is unchanged, because colour tracks frequency, not wavelength. Pick a medium in the Light & photons tab to see both wavelengths side by side.
What is the wavelength range of visible light?+
Roughly 380 nm (violet) to 750 nm (red). Shorter than 380 nm you are in ultraviolet, then X-rays and gamma rays; longer than 750 nm lies infrared, then microwaves and radio waves.
Visible light covers less than an octave of frequency — a narrow window of the full electromagnetic spectrum.
How are wavelength, frequency and period related?+
Frequency counts cycles per second; period is its flip side in seconds per cycle: T = 1 ÷ f. Wavelength connects them to speed through v = λ × f.
A 100 MHz FM radio wave, for instance, repeats every 10 ns and measures about 3 m from crest to crest.
How do I convert wavelength to photon energy?+
Use E = h × c ÷ λ, where h = 6.626×10−34 J·s is Planck’s constant. Divide the energy in joules by 1.602×10−19 to get electronvolts.
A shortcut worth memorising: λ(nm) × E(eV) ≈ 1240 — handy for quick estimates in physics and chemistry exams.
Is the calculator free, and is my data sent anywhere?+
It is completely free and runs entirely in your browser — nothing you type is uploaded, logged or sent to a server.
No account, no sign-up, no limits, and it keeps working offline once the page has loaded.