Frequency Counter+ Hz FFT

Frequency Counter+ turns your iPhone into a precise audio analyzer with four purpose-built modes. Measure the dominant frequency of any sound, tune an instrument, read motor RPM by ear, or check the stability of your 50/60 Hz mains.

FOUR MODES
• Music — instrument tuner showing note name (A4, F#5) and cents off pitch (A4=440 Hz).
• Motor — RPM displayed first, with hints for 1500/1800/3000/3600 RPM standards.
• Hum — 50/60 Hz mains lock with deviation in ±0.01 Hz.
• Auto — Hz reading with closest musical note or mains harmonic shown live.

WHAT'S NEW
• Measurement History — every reading is auto-saved with a 7-day trend chart and insights like "+12% vs your 7-day average".
• Notes & Favorites — add a note ("fridge", "room 1") and star to any saved reading.
• Compare Mode — pick two saved measurements and view the difference side by side.
• Calibration Offset — fine-tune your microphone in ±0.1 Hz steps.
• Share Result — share your current frequency reading as an image.
• CSV Export — share all your measurements as CSV for spreadsheets.

CORE FEATURES
• Precise dominant frequency measurement (Hz)
• Large multimeter-style digital display
• Automatic 50/60 Hz mains hum detection with lock indicator
• Instant Hz-to-RPM conversion
• Waveform and amplitude visualization
• Microphone calibration

FOR MUSICIANS · AUDIO ENGINEERS · ELECTRICIANS · MECHANICS · HVAC TECHS · INDUSTRIAL DIAGNOSTICS

Available in 14 languages.