What is a frequency ratio?

A frequency ratio expresses how many times higher one frequency is than another. A ratio of 2:1 means an octave; 3:2 is a just perfect fifth.

Cents divide each equal-temperament semitone into 100 equal parts, giving 1200 cents per octave. They are computed as 1200 × log₂(f₂/f₁).

How is the interval name determined?

The calculator rounds the absolute cents value to the nearest semitone (100 cents) and maps it to a standard interval name (Unison, Minor 2nd … Octave).

Can I use note names instead of Hz?

Yes. Type a note name like A4, C#5, or Bb3 and the calculator converts it to Hz using A4 = 440 Hz as the reference.

What is the difference between just and equal-temperament ratios?

Just ratios use small whole-number fractions (e.g. 3:2) and sound pure; equal-temperament ratios are irrational numbers (2^(n/12)) that allow modulation to any key.

Interval Ratio Calculator

Name: Interval Ratio Calculator
Availability: InStock
Author: Nham Vu

Enter two frequencies (or note names) to instantly get the frequency ratio, cents value, and musical interval name.

Enter Two Frequencies

Frequency 1 (Hz or note name, e.g. A4)

Frequency 2 (Hz or note name, e.g. E5)

Quick Examples

Enter two frequencies and click Calculate

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Summary

Enter two frequencies (or note names) to instantly get the frequency ratio, cents value, and musical interval name.

How it works

Given frequencies f1 and f2, the ratio is f2/f1. Cents are computed as 1200 × log2(f2/f1). The closest standard equal-temperament interval is identified by rounding the cents value to the nearest 100-cent step.

Use cases

Verify tuning accuracy by comparing a played frequency to the target note.
Analyze microtonal intervals and detuning amounts in cents.
Explore just-intonation ratios vs. equal-temperament for any interval.
Understand harmonic relationships between overtone series partials.
Cross-check synthesizer pitch modulation depths.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu