# Semitone Calculator

Calculate frequency ratios and intervals between musical notes. Shift by semitones, see interval names, frequencies, and cents. Supports custom tuning.

## What this calculates

Select a starting note and shift by any number of semitones to see the resulting frequency, interval name, and frequency ratio. This calculator uses equal temperament tuning and lets you adjust the A4 reference pitch for historical or alternative tuning systems.

## Inputs

- **Starting Note** — options: C3 (130.81 Hz), D3 (146.83 Hz), E3 (164.81 Hz), F3 (174.61 Hz), G3 (196.00 Hz), A3 (220.00 Hz), B3 (246.94 Hz), C4 - Middle C (261.63 Hz), D4 (293.66 Hz), E4 (329.63 Hz), F4 (349.23 Hz), G4 (392.00 Hz), A4 - Concert Pitch (440 Hz), B4 (493.88 Hz), C5 (523.25 Hz), D5 (587.33 Hz), E5 (659.26 Hz), F5 (698.46 Hz), G5 (783.99 Hz), A5 (880.00 Hz), B5 (987.77 Hz), C6 (1046.50 Hz)
- **Semitones to Shift** — min -48, max 48 — Positive = up, negative = down. 12 = one octave.
- **Tuning Reference (A4)** (Hz) — min 400, max 480 — Standard concert pitch is 440 Hz. Baroque tuning uses 415 Hz.

## Outputs

- **Starting Frequency**
- **Resulting Frequency**
- **Frequency Ratio**
- **Interval Name** — formatted as text — Musical name for this interval
- **Cents** — Interval size in cents (100 cents = 1 semitone)

## Details

In equal temperament (the standard tuning system), each semitone raises the pitch by a factor of 2^(1/12), which is approximately 1.05946. Twelve semitones make one octave, which doubles the frequency.

Common intervals and their semitone counts:

  - Minor 3rd: 3 semitones (ratio 1.189)

  - Major 3rd: 4 semitones (ratio 1.260)

  - Perfect 4th: 5 semitones (ratio 1.335)

  - Perfect 5th: 7 semitones (ratio 1.498)

  - Octave: 12 semitones (ratio 2.000)

Cents are a finer subdivision. One semitone = 100 cents. Cents are useful for measuring tiny pitch differences, like the 2-cent detuning between equal temperament and just intonation thirds.

## Frequently Asked Questions

**Q: What is a semitone?**

A: A semitone (or half step) is the smallest interval in standard Western music. On a piano, it is the distance between any two adjacent keys (including black keys). On a guitar, it is one fret. Twelve semitones make up one octave.

**Q: Why is A4 set to 440 Hz?**

A: The A4 = 440 Hz standard was adopted internationally in 1955 (ISO 16). Before standardization, concert pitch varied by region and era. Baroque orchestras commonly used A4 = 415 Hz, and some modern orchestras tune to 442 or 443 Hz for a slightly brighter sound.

**Q: What is the difference between equal temperament and just intonation?**

A: Equal temperament divides the octave into 12 equal semitones, making all keys sound equally in tune (or equally slightly out of tune). Just intonation uses pure frequency ratios (like 3:2 for a fifth) which sound more harmonically pure in one key but increasingly out of tune in distant keys.

**Q: How are cents used in music?**

A: Cents measure tiny pitch differences. One semitone = 100 cents. A trained ear can detect differences of about 5-10 cents. Cents are useful for comparing tuning systems, measuring vibrato width, checking instrument intonation, and describing microtonal intervals.

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Source: https://vastcalc.com/calculators/everyday/semitone
Category: Everyday Life
Last updated: 2026-04-08