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.