Frequency Calculator
Calculate frequency from a period or from wave speed and wavelength. Get frequency in Hz and kHz plus angular frequency, with the formula and steps shown.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Frequency Calculator Works
Frequency is how many cycles of a repeating event happen each second, measured in hertz (Hz). This calculator offers two modes: find frequency from a period, or from a wave speed and wavelength. It returns the frequency in Hz and kHz, plus the angular frequency.
The Formula
The two standard ways to find frequency are:
From a period: f = 1 ÷ T From a wave: f = v ÷ λ
Here T is the period in seconds, v is the wave speed in meters per second and λ is the wavelength in meters. The angular frequency is ω = 2π × f, in radians per second.
Worked Example
A sound wave travels at v = 343 m/s with a wavelength of λ = 0.78 m:
- f = 343 ÷ 0.78 = ≈ 440 Hz (the musical note A4)
- ω = 2π × 440 = ≈ 2,765 rad/s
If instead you knew the period was T = 0.02 s:
- f = 1 ÷ 0.02 = 50 Hz
Period and Frequency Reference
| Period T | Frequency f |
|---|---|
| 1 s | 1 Hz |
| 0.1 s | 10 Hz |
| 0.02 s | 50 Hz |
| 0.001 s | 1,000 Hz (1 kHz) |
Choosing the Right Wave Speed
When using the wave method, use the correct speed for your medium. Sound in air is about 343 m/s at room temperature, while electromagnetic waves (light, radio, microwaves) travel at the speed of light, 299,792,458 m/s in a vacuum. Using the wrong speed will scale your frequency incorrectly, so match the speed to the kind of wave you are analyzing.
Frequently asked questions
How do you calculate frequency?+
Frequency is the number of cycles per second, measured in hertz. From a period it is f = 1 ÷ T, where T is the time for one cycle in seconds. From a wave you can also use f = v ÷ λ, dividing the wave speed by the wavelength. The calculator supports both methods.
What is the relationship between frequency and period?+
Frequency and period are reciprocals: f = 1 ÷ T and T = 1 ÷ f. A period of 0.02 seconds means 50 cycles per second, or 50 Hz. The shorter the period, the higher the frequency, because more cycles fit into each second.
How do I find frequency from wavelength?+
Divide the wave speed by the wavelength: f = v ÷ λ. For sound in air, v is about 343 m/s; for light or radio in a vacuum, v is the speed of light, 299,792,458 m/s. A wavelength of 0.78 m of sound gives about 440 Hz, roughly the musical note A4.
What is angular frequency?+
Angular frequency ω describes how fast a wave rotates in phase, in radians per second, and equals 2π times the ordinary frequency: ω = 2πf. It appears in equations for oscillation and AC circuits. A 50 Hz signal has an angular frequency of about 314 rad/s.
What units does this frequency calculator use?+
Period is entered in seconds, wave speed in meters per second and wavelength in meters. The result is shown in hertz and kilohertz, plus angular frequency in radians per second. Keep your inputs in these SI units for a correct answer.