DTMF Tone Generator

Press a key to hear its touch tone. Type a number and press Play number to dial it, or decode tones with the decoder below.

Press a key to hear its tone pair

Volume
-12 dB
Call progress tones

DTMF decoder

Decode touch tones from your microphone (hold the phone or speaker close) or from an audio file. Everything is processed in your browser.

How to use the DTMF generator

  1. Press keys on the keypad, or use your keyboard’s number keys plus * and #. The tone plays for as long as you hold the key, and the two frequencies are shown above the keypad. Multi-touch works, so you can press two keys at once to hear how a decoder handles it.
  2. Dial a sequence: the keys you press collect in the number field. You can also type or paste a number. Press Play number (or Enter) to play it with precise timing, and change Tone length and Gap for slow or fast dialing.
  3. Download the sequence as a WAV file to use in an IVR prompt, a test or a video.
  4. Call progress tones play the dial, ringback and busy tones used in the US and UK. Click again to stop.
DTMF tone generator with key 5 pressed, showing 770 Hz and 1336 Hz, plus the dial field, play and download buttons, timing options and call progress tones labeled
  1. The number you’re dialing. Pressed keys are added here, and you can type too.
  2. The two frequencies of the key you pressed.
  3. Hold a key to play its tone.
  4. Play the whole number, or download it as a WAV.
  5. Tone length and gap between digits.
  6. Dial tone, ringback and busy tones.

DTMF frequency table

Each key combines one row frequency and one column frequency. Click a key to hear it. The frequencies were chosen so that no frequency is a harmonic of another, which keeps speech and music from accidentally triggering them.

1209 Hz1336 Hz1477 Hz1633 Hz
697 Hz
770 Hz
852 Hz
941 Hz

Hear the two groups separately: the low (row) tones and the high (column) tones .

How DTMF decoding works

A decoder has to answer two questions about every few milliseconds of audio: is a DTMF tone present, and which one? The decoder on this page does what telephone exchanges do:

  1. Measure the eight frequencies. The Goertzel algorithm is a cheap way to measure the energy at a handful of specific frequencies. It’s like an FFT that only computes the bins you care about. The decoder analyzes a 40 ms window of audio every 10 ms.
  2. Pick the strongest tone in each group and require it to be clearly stronger (about 8 dB or more) than the others in its group.
  3. Check that the two tones dominate. Together they must carry most of the signal’s energy, which rejects speech, music and noise that happen to contain those frequencies.
  4. Check the “twist”, the level difference between the high and low tone. Real lines attenuate high frequencies, so some difference is normal, but more than about 8 dB isn’t a valid tone.
  5. Require a minimum duration (two consecutive windows) and a release between repeats, so a long press counts once and 5-5-5 counts three times.

The decoder rejects frequencies more than about 3.5% off, as the standard requires, and accepts tones from about 40 ms long at standard telephone quality (8 kHz) or better.

Call progress tones

ToneFrequenciesPattern
US dial tone350 + 440 HzContinuous
US ringback440 + 480 Hz2 s on, 4 s off
US busy480 + 620 Hz0.5 s on, 0.5 s off
US fast busy (reorder)480 + 620 Hz0.25 s on, 0.25 s off
UK dial tone350 + 450 HzContinuous
UK ringback400 + 450 Hz0.4 s on, 0.2 s off, 0.4 s on, 2 s off

These are the North American “Precise Tone Plan” and the UK (BT) standards. Other countries use different tones. Much of Europe, for example, uses a single 425 Hz tone, which you can play with the tone generator.

What DTMF is used for

  • Testing phone menus (IVR): download a WAV of a menu path, such as 1,,2,,# with pauses, and play it into a call to step through the menu the same way every time.
  • Amateur radio: repeaters and linking systems (EchoLink, AllStar) are controlled with DTMF codes, often including the A–D keys.
  • Retro phones and electronics: check that an old Touch-Tone phone or a DTMF decoder chip (such as the MT8870) is working, or generate tones for Arduino projects.
  • Forensics and curiosity: decode the number dialed in a recording or video. If the dialing tones are audible, the decoder will usually recover the digits.
  • Sound design: authentic phone keypad sounds for film, games and podcasts.

Frequently asked questions

What does DTMF stand for?

Dual-Tone Multi-Frequency. Every key on a phone keypad sends two sine tones at once: one from a low group (697, 770, 852 or 941 Hz) that identifies the row, and one from a high group (1209, 1336, 1477 or 1633 Hz) that identifies the column. Bell Labs introduced it in 1963 as “Touch-Tone” to replace rotary pulse dialing.

Can I dial a real phone number by playing tones into my phone?

Usually not to start a call, because modern mobile and VoIP phones dial digitally rather than listening for tones. But once you’re in a call, tones played into the microphone (or from this page through a speaker held close to the phone) work with most automated menus, voicemail systems and conference bridges. Many carriers pass them through as audio or convert them to RFC 4733 events.

How do I decode DTMF tones from a recording?

Click Decode a file in the DTMF decoder above and choose the recording (WAV, MP3, M4A, OGG or FLAC). The decoder scans the whole file and shows every key it finds. For live audio, click Listen with microphone and play the tones near your mic. Tones should be at least 40 ms long and not heavily distorted.

What are the A, B, C and D keys for?

They complete the 4×4 grid using the fourth high-group frequency (1633 Hz). They were used by the US military’s AUTOVON network to set call priority (Flash Override, Flash, Immediate, Priority), and today they show up in ham radio repeater control, some alarm panels, and telephone test equipment. Consumer phones don’t have them. Tick Show A–D keys to use them.

What tone length and gap should I use?

The ITU-T Q.24 recommendation says receivers must accept tones of 40 ms or longer, and most phones send around 70–100 ms with a similar gap. 100 ms on and 100 ms off is a safe default for menus and decoders. Some older systems or radio links need longer tones (150–250 ms). Use 50 ms only to test how fast a decoder can keep up.

Why does the decoder miss tones from my microphone?

Common causes are background noise or speech over the tones, a speaker that distorts at high volume, a phone that processes the audio heavily, or tones shorter than about 40 ms. Move the mic closer, lower the speaker volume a little, and make sure no noise suppression is running. The decoder already turns off the browser’s own suppression.

Can I type letters, like 1-800-FLOWERS?

Yes. Letters are converted to their keypad digits (F = 3, L = 5, and so on). Dashes, spaces and brackets are ignored, and a comma inserts a half-second pause, as on many phones. When Show A–D keys is on, the letters A–D send the DTMF A–D tones instead.

Tone GeneratorPlay any frequency from 1 Hz to 22 kHz in four waveforms.Test TonesDownload WAV test tones, sweeps and noise for calibration.Mic TestCheck your microphone with live levels, playback and diagnostics.Spectrum AnalyzerLive frequency spectrum and spectrogram from your mic.