DTMF Tone Generator
Press and hold a key to hear its touch tone, or type a phone number and play the whole dialing sequence with your own tone and gap lengths. Download it as a WAV file, or switch to Detect to decode DTMF digits from your microphone or a recording.
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Digits 0–9, * and #. A–D are the extra DTMF tones. A comma adds a pause. Spaces, dashes, dots and brackets are ignored.
Press Start listening and play DTMF tones near your microphone, or open an audio file.
Detection uses the Goertzel algorithm on the 8 DTMF frequencies, with twist and energy checks to reject speech and music. Audio never leaves your device.
How to use the DTMF Tone Generator
- Tap a key on the keypad (or press it on your keyboard) to hear its two DTMF frequencies for as long as you hold it.
- Type a number in Number to dial. Use commas for pauses and tick the letters option for vanity numbers.
- Set the timing: tone and gap length in milliseconds (70 ms each is a fast auto-dialer, 100–150 ms is typical).
- Press Play sequence to hear it, or Download WAV to save it for an IVR menu, a test or a video.
- To decode, open Detect / decode, press Start listening and play tones near the microphone, or choose an audio file.
DTMF frequency table
Each key is the sum of one row tone and one column tone. Pressing 5 sends 770 Hz and 1336 Hz together. The frequencies were chosen so that no tone is a harmonic of another, which makes them easy to tell apart from speech.
| 1209 Hz | 1336 Hz | 1477 Hz | 1633 Hz | |
|---|---|---|---|---|
| 697 Hz | 1 | 2 | 3 | A |
| 770 Hz | 4 | 5 | 6 | B |
| 852 Hz | 7 | 8 | 9 | C |
| 941 Hz | * | 0 | # | D |
Uses and good practice
- Testing phone menus (IVR): download a WAV with the exact digits and timing you need and play it into a call or test system.
- Video and sound design: real keypad tones for dialing scenes; export at 8 kHz for an authentic telephone sound.
- Radio and remote control: amateur radio repeaters and some remote switches are controlled by DTMF codes, often including A–D.
- Reading a recording: the decoder can recover digits dialed in a voicemail or video. Only decode recordings you are allowed to analyse.
Each tone is generated as x(t) = A·sin(2π·frow·t) + A·sin(2π·fcol·t) with a 4 ms fade in and out to avoid clicks. Both tones have the same level, so the twist (level difference between the two tones) is 0 dB.
Frequently asked questions
What is DTMF?
DTMF (dual-tone multi-frequency) is the touch-tone signalling used by telephone keypads. Each key sends two sine waves at the same time: one from a low group (697, 770, 852 or 941 Hz) for its row and one from a high group (1209, 1336, 1477 or 1633 Hz) for its column. The standard is ITU-T Recommendation Q.23.
What frequencies does each key use?
Row frequencies are 697 Hz (1 2 3 A), 770 Hz (4 5 6 B), 852 Hz (7 8 9 C) and 941 Hz (* 0 # D). Column frequencies are 1209 Hz (1 4 7 *), 1336 Hz (2 5 8 0), 1477 Hz (3 6 9 #) and 1633 Hz (A B C D). For example 5 is 770 Hz + 1336 Hz.
What are the A, B, C and D keys?
They are a fourth column of DTMF tones at 1633 Hz that most phones do not have. They were used on military AUTOVON phones and are still used by some radio, paging and control systems. Tick Show A B C D keys to use them.
How long should each tone be?
Q.24-based telephone equipment generally accepts tones of about 40 ms or longer with gaps of about 40 ms or longer. Phones usually send 70–100 ms tones, and 100–150 ms with similar gaps is a safe choice for answering machines and phone menus.
How does the decoder work?
It measures the strength of the eight DTMF frequencies about every 13 ms with the Goertzel algorithm. A key is accepted when one low and one high frequency clearly dominate, their levels are within the allowed twist, and the result is stable for two measurements in a row.
Why are some digits not detected?
Background noise, music, speech, a very quiet signal or very short tones can stop detection. Hold the phone close to the microphone, raise the volume, avoid audio compression where possible, or set Sensitivity to High. Phone calls often filter or compress DTMF, so a direct recording works best.
Is anything uploaded?
No. Tones are generated and recordings are analysed entirely in your browser. Microphone audio is processed live and discarded.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.