440 Hz Tone Generator Online — Free Concert A Reference
Play a pure, precise 440 Hz tone online — the international standard concert pitch (A4) — directly in your browser. Free, instant, no install. Perfect for tuning guitars, violins, pianos, and any acoustic instrument.
What is 440 Hz?
440 Hz is the international standard frequency for musical pitch — it represents the note A above middle C (A4). Since 1955, ISO 16 has defined 440 Hz as the reference frequency for tuning orchestras, pianos, and electronic instruments worldwide. When a musician says "tuning to 440," they mean their A4 string or note vibrates exactly 440 times per second.
Our online 440 Hz tone generator produces a mathematically pure sine wave at exactly 440 Hz using the browser's Web Audio API — making it perfect for tuning any acoustic instrument by ear, calibrating digital tuners, or comparing with 432 Hz alternative tuning.
Features
Exact 440.00 Hz
Mathematically precise reference pitch — no drift, no jitter, perfect Concert A.
Built for Tuning
Hold the tone as long as you need and tune your instrument by ear without rush.
Compare 432 vs 440
One-tap presets to A/B test 432 Hz, 440 Hz, 442 Hz, and 444 Hz tunings.
Works Everywhere
Tune on iPhone, Android, laptop, or studio computer — no app or signup required.
Zero Latency
Web Audio API plays the tone instantly with sample-accurate frequency.
Volume-Safe Defaults
Smooth fade-in prevents speaker pops. Always start at low volume.
Common Uses
Tune your 5th string (A) to 440 Hz, then tune the other strings relative to it.
Piano technicians use 440 Hz as the unison reference before stretching octaves.
Singers use a steady 440 Hz to practice pitch matching and ear training.
Verify that your digital tuner or app is reading the correct reference pitch.
How to Use
1. Choose Waveform
Pick sine, square, sawtooth, or triangle depending on the tone character you need.
2. Set Frequency
Use the slider or tap a preset to dial the exact frequency you need.
3. Adjust Volume
Start at low volume — pure tones can be louder than they feel.
4. Press Play
Hit Play and the tone keeps playing continuously until stopped.
Frequently Asked Questions
In 1939 an international conference adopted A4 = 440 Hz as the standard concert pitch, and ISO 16 formalised it in 1955. Most orchestras, instrument makers, and digital tuners worldwide use 440 Hz as their reference.
Neither is objectively "better". 440 Hz is the global standard and ensures instruments play in tune with each other. 432 Hz is an alternative many musicians find warmer or more relaxing — try both with our presets and decide for yourself.
Play the 440 Hz tone, then pluck your open A (5th) string and adjust the tuning peg until the two pitches match. Once A is in tune, use it as the reference for the other strings.
Yes — the Web Audio API generates the tone at exactly 440.00 Hz with floating-point precision. Actual playback accuracy is limited only by your device's audio clock, which is typically accurate to within a few cents.
Currently no — but the tone plays continuously for as long as you need it. Recording the live output with your DAW is the simplest way to capture it.
Hearing Safety
Pure tones — especially below 40 Hz or above 10 kHz — carry significant energy at high volumes. Start low and protect your hearing and speakers.