−12 Semitones (One Octave Down) Frequency Ratio
Dropping by 12 semitones lowers the pitch by one octave, giving a frequency ratio of 0.5.
How to use this tool
- Enter semitones in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your frequency ratio and the full breakdown beneath it.
Transposing down one octave halves the frequency, corresponding to −12 semitones in equal temperament.
Frequently asked questions
- What is the frequency ratio of an octave?
- An octave is exactly 12 semitones, corresponding to a frequency ratio of 2:1.
- What is the perfect fifth ratio?
- A perfect fifth is 7 semitones; the equal-temperament ratio is 2^(7/12) ≈ 1.4983.