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.