French A435 quick reference
- A4 reference
- 435 Hz
- Relative to A440
- -19.8 cents
- Meter range
- A0–C8
What this reference means
The historical French diapason normal reference established in 1859.
A435 is useful when studying historical pitch and period performance practice.
Sample calculated key targets
The meter applies the same formula to all 88 keys. These sample values make the selected reference visible before microphone use.
| Piano key | Note | MIDI | Frequency |
|---|---|---|---|
| 1 | A0 | 21 | 27.19 Hz |
| 40 | C4 | 60 | 258.65 Hz |
| 49 | A4 | 69 | 435.00 Hz |
| 52 | C5 | 72 | 517.31 Hz |
| 88 | C8 | 108 | 4138.44 Hz |
Need every key? Open the interactive 88-key frequency chart.
Instrument safety and scope
A modern piano is normally maintained near its intended design pitch; consult a technician before changing it.
Method and sources
Each displayed target uses frequency = 435 × 2((MIDI − 69) / 12). This is a transparent equal-temperament calculation. A real piano's string inharmonicity leads technicians to stretch octaves, so a browser target is not a complete tuning curve.
French A435 FAQ
What does French A435 mean?
The historical French diapason normal reference established in 1859. A435 is useful when studying historical pitch and period performance practice.
Does this page really use A4 = 435 Hz?
Yes. Every key target is recalculated from A4 = 435 Hz using the 12-tone equal-temperament formula. The selected reference changes both automatic note matching and fixed-key targets.
Can I retune an acoustic piano to 435 Hz with this page?
This page can measure and compare pitch, but it cannot assess the instrument's structure, unisons, stretch, or stability. Ask a qualified piano technician before changing an acoustic piano's overall pitch.