Chord calculator
C major is C, E and G, stacked at 0, 4 and 7 semitones from the root. Enter a root such as F# or Bb and a type from major to ninths to get the spelled notes and the interval formula. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Root
- C
- Chord type
- Major
- Note count
- 3
- Intervals semitones
- 0, 4, 7
A chord is an ordered stack of pitch classes built from a single root note and a named type such as major, minor, diminished, augmented, or dominant seventh. Guitarists checking a voicing, pianists filling a lead sheet, songwriters testing a progression, and theory students spelling homework all need the same answer: which notes sit inside C major, F sharp minor, B flat dominant seventh, or G suspended fourth, written in stacking order from the root. This chord calculator accepts a root such as C, F sharp, or B flat and a chord type from a published catalog, then returns the spelled notes, the note count, the semitone offsets from the root, and a compact interval formula.
How a root and a chord type become an ordered note list
Western equal temperament divides the octave into twelve semitones. Each letter A through G has a base pitch class on that circle: C is zero, D is two, E is four, F is five, G is seven, A is nine, and B is eleven. Accidentals shift the class by whole semitones before the value is reduced modulo twelve, so F sharp and G flat share a class while keeping different spellings that musicians actually write.
A chord type is then a frozen recipe of offsets from that root. A major triad uses a major third and a perfect fifth (four and seven semitones). A minor triad lowers the third to three semitones.
Diminished and augmented triads move the fifth to six and eight. Suspended second and fourth replace the third with two or five semitones. Dominant, major, and minor sevenths add ten or eleven.
Diminished seventh and half-diminished add nine or ten above a diminished fifth. Sixths add nine. Ninths and add-nine shapes reach fourteen.
A power chord keeps only the root and the fifth. This calculator walks generic interval letters from the root—thirds for tertian stacks, a second or a fourth for suspensions—and attaches the accidental that hits each target pitch class. That is why C major spells C E G, F sharp major spells F sharp A sharp C sharp, B flat minor spells B flat D flat F, and C diminished seventh spells C E flat G flat B double-flat rather than a random mix of enharmonic names.
Where chord calculators show up in real work
Music theory classes assign chord-spelling drills, quality identification, and lead-sheet checks every week; a single trusted oracle that returns both the note list and the interval formula speeds grading and demo setup without arguing about enharmonic choices. Songwriters exploring a progression need a quick, correct list of tones in D minor seventh or B flat major before they invent a melody that fights the harmony.
Ear-training and mobile practice apps require a deterministic backend so progressive lessons never disagree with the classroom chalkboard on whether F sharp major includes A sharp. Session musicians checking a chart on a phone can paste a root and pick a type without installing a DAW plugin.
If you later need the notes of a scale rather than a chord, the sounding key after a capo, a transposition of an existing symbol, or the frequency of a single pitch, treat those as separate search intents and landings rather than overloading this chord page. This calculator returns pitch-class names in stacking order only: it does not voice chords across octaves, suggest guitar fingerings, analyze audio, or invent jazz alterations outside the published type table.
What you can do with it
Theory homework and answer keys
Generate spelled note lists and interval formulas for textbook roots and types so teachers and auto-graders share one ground truth.
Practice sheets and warm-up builders
Fill guitar, piano, or voice warm-up sheets for a chosen root and chord type without hand-writing accidentals.
Songwriting and chart checks
List the tones inside a major, minor, seventh, or suspended chord before drafting a melody, voicing, or lead-sheet symbol.
FAQ
What root spellings can I enter?
Letters A–G with optional accidentals (#, b, x, ##, bb, ♯, ♭), for example C, F#, Bb, or Eb. Optional octave digits are accepted and ignored for spelling.
How is C major different from A minor?
They share pitch classes but stack from different roots: C major is C E G; A minor is A C E. The response always begins on the root you requested and follows that type's interval recipe.
Are enharmonic roots treated the same?
Pitch class is the same for C# and Db, so interval steps match, but spelling follows the root letter you typed, so C# major and Db major keep different accidental families.
What does it cost?
The browser tool is free and runs locally.
What notes are in G dominant seventh?
G, B, D and F: a major triad on G with a minor seventh added above the root. The notes come in stacking order from the root, spelled the way you would write them on a lead sheet.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/hobby/chord \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"root":"C","chord_type":"major"}'const res = await fetch("https://api.kit.forhosting.com/hobby/chord", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"root": "C",
"chord_type": "major"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/hobby/chord",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"root": "C",
"chord_type": "major"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/hobby/chord", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"root":"C","chord_type":"major"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"root":"C","chord_type":"major"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/hobby/chord", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"root": "C",
"chord_type": "major"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "hobby.chord",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Unrecognized roots and unrecognized chord types fail with a clear invalid_input error instead of inventing a bogus stack of pitches.
How a root and a chord type become an ordered note list
Empty fields, letters outside A through G, and types outside the catalog fail early with invalid_input naming the problem so clients can highlight the bad field without guessing. The entire pipeline is pure deterministic arithmetic: no random seeds, no wall-clock timestamps, no network calls, and no model drift, so the same root and chord type always produce the same JSON.
What you send and what you get back
Root may be a bare pitch class such as C, F sharp written F#, B flat written Bb, or a double accidental such as C## or Dbb; unicode sharp and flat signs are accepted; an optional octave digit is ignored because a chord type is pitch-class material, not a single MIDI register. Spaces, hyphens, and mixed case normalize to the same key, so Half Diminished and half-diminished both resolve. Single-letter M versus m is kept case-sensitive so a capital M still means major and a lowercase m still means minor. Classic checks include C major as C E G, A minor as A C E, G dominant seventh as G B D F, and F sharp major as F# A# C#. Send root as a note string and chord_type as a type string. Chord type accepts canonical catalog names and common aliases: major or maj, minor or min, diminished or dim, augmented or aug, sus2, sus4, dominant7 or 7 or dom7, major7 or maj7, minor7 or min7, diminished7 or dim7, half_diminished or m7b5, sixth or 6, minor_sixth or m6, ninth or 9, add9, and power or 5. Aliases include note, tonic, and pitch for the root, and type, quality, and chord for the type. Missing required fields, empty strings, unrecognized roots, and unrecognized chord types fail with invalid_input and are not charged. On success the response echoes the root you typed, returns chord_type as the canonical catalog name, notes as the ordered list of spellings from the bass of the stack upward, note_count, intervals_semitones, a hyphenated formula such as 0-4-7, and method tertian_letter_spelling for tests. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where chord calculators show up in real work
Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.
Technical questions
Which chord types are supported?
Major, minor, diminished, augmented, sus2, sus4, dominant7, major7, minor7, diminished7, half_diminished, sixth, minor_sixth, ninth, add9, and power. Common aliases such as maj, min, 7, maj7, m7, dim7, m7b5, 6, and 5 are accepted. Unknown names return invalid_input.