Frequency Counter: Hz Meter

Frequency Counter is an audio frequency meter, Hz counter, and instrument tuner for Android. Measure the dominant sound frequency in real time with your phone's microphone — no extra hardware needed.

Turn your Android phone into a four-in-one frequency lab: read any tone in hertz, tune instruments, count RPM, and verify 50/60 Hz mains hum.

▶ MAIN FEATURES

• Frequency meter — dominant frequency in Hz, live from the microphone

• Instrument tuner — tune guitar, piano, violin and more with cents precision

• RPM counter — measure rotation speed from sound or vibration

• 50/60 Hz mains mode — check power-line and electrical hum frequency

• Real-time FFT with high-resolution peak detection (20 Hz–20 kHz)

• Adjustable averaging, smoothing and sensitivity

• Hold mode to freeze the reading

• Dark mode, works fully offline, no account needed

▶ HOW TO USE

1. Open Frequency Counter and allow microphone access

2. Pick a mode: frequency, tuner, RPM or 50/60 Hz mains

3. Point the phone at the sound source

4. Read the live frequency in hertz, the musical note, or the RPM

▶ WHO USES FREQUENCY COUNTER

• Musicians and instrument makers tuning by exact frequency

• Audio and AV engineers checking tones and signal pitch

• Electricians and technicians verifying 50/60 Hz mains

• Mechanics and makers measuring motor and fan RPM

• Piano tuners needing cents-accurate pitch

• Students learning acoustics, sound and signal processing

• DIY hobbyists testing speakers, buzzers and alarms

Microphone permission required. External USB microphones supported.