Note from interval and root calculator
A perfect fifth above C is G, and a major third above F sharp is A sharp, not B flat: pick a root, an interval from unison to octave and a direction, and get the correctly spelled note. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Root
- C
- Interval
- P5
- Direction
- Above
- Interval name
- Perfect Fifth
- Interval quality
- perfect
- Interval number
- 5
- Note name
- G
Finding the pitch that sits a named interval above or below a given root is the everyday inverse of naming the distance between two notes. Students type what note is a perfect fifth above C; songwriters ask for a major third below F sharp; arrangers need the octave above B flat with the correct letter spelling. This note from interval and root calculator accepts a root such as C, F#, Bb, or C4, a named interval from the closed simple catalog (unison through octave, including diminished and augmented qualities plus the tritone), and a direction of above or below. It returns the destination note spelled with the proper diatonic letter, so a major third above F sharp is A sharp rather than B flat.
How a named interval becomes a spelled destination note
Western tonal theory names an interval by two facts at once: a diatonic number that counts letter names inclusive of the root (a fifth always lands on the fifth letter, C through G), and a quality that fixes the exact size in equal-tempered semitones (a perfect fifth is seven semitones, a diminished fifth is six). This calculator applies that pair to a root instead of measuring two given pitches.
First the root is parsed into a letter A through G, an accidental offset from sharps, flats, or double sharps written as x or two hash marks, and an optional octave digit that later yields a MIDI number with middle C as sixty.
Next the interval token is looked up in a closed table: P1 is zero semitones and number one, m3 is three semitones and number three, P5 is seven and five, P8 is twelve and eight, TT is the tritone spelled as an augmented fourth, and the remaining diminished and augmented simple sizes complete the catalog. Direction chooses the sign: above adds the letter offset and the semitones; below subtracts them.
The destination letter is the root letter advanced by the interval number minus one, wrapping around the seven-note cycle and carrying the octave when that wrap crosses C or when the interval itself is an octave. The destination accidental is then the unique offset that makes that letter match the target pitch class. That is why F sharp plus a major third is A sharp, not B flat: the third must be some kind of A.
Where a note-from-interval calculator earns its keep
Theory classrooms assign the inverse drill of interval identification: given a root and a printed name such as perfect fifth or minor sixth, write the destination pitch with the correct accidental. A single trusted oracle that spells letters diatonically speeds grading and demo setup without a teacher re-deriving every pair. Ear-training and mobile practice apps need a deterministic backend so that a prompt for a major third above F sharp never awards B flat as correct.
Songwriters, guitarists, and arrangers sketching melody leaps want the note a perfect fourth below the current tone before they commit to voice-leading or a capo chart. Keep roots inside letter-plus-accidental spelling, pick a catalog interval, choose above or below, and you get reproducible theory answers for homework, LMS plugins, and edge workers without standing up a notation stack.
What you can do with it
Theory homework and answer keys
Generate the destination pitch for textbook prompts such as “perfect fifth above C” or “major third below F#” so teachers and auto-graders share one spelled ground truth.
Arranging and melody leaps
Look up the pitch a named interval above or below the current tone before committing a leap, inner voice, or capo transposition.
FAQ
How do I find the note a perfect fifth above C?
Send root "C", interval "P5", and direction "above". The destination note is G. With an octave on the root (C4) the note is G4 and a MIDI number is included.
Why is a major third above F sharp written A sharp, not B flat?
A third must land on the third letter from the root. F–G–A is a third, so the quality (major, four semitones) adjusts the accidental on A, giving A#. Bb is a fourth letter from F and would be a diminished fourth, not a third.
What is the difference between this and a musical interval calculator?
A musical interval calculator takes two notes and names the distance between them. This tool takes one root plus a named interval and returns the other note. They are inverse search intents.
Can I go below the root, or use an octave?
Yes. direction "below" subtracts the interval (C4 plus P5 below is F3). An optional octave 0–9 on the root is copied through letter wrap so destination octave and MIDI are reported.
What does the note from interval calculator cost?
The browser tool is free and runs locally.
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/music-note-from-interval \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"root":"C","interval":"P5","direction":"above"}'const res = await fetch("https://api.kit.forhosting.com/hobby/music-note-from-interval", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"root": "C",
"interval": "P5",
"direction": "above"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/hobby/music-note-from-interval",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"root": "C",
"interval": "P5",
"direction": "above"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/hobby/music-note-from-interval", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"root":"C","interval":"P5","direction":"above"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"root":"C","interval":"P5","direction":"above"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/hobby/music-note-from-interval", 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",
"interval": "P5",
"direction": "above"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "hobby.music_note_from_interval",
"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
How a named interval becomes a spelled destination note
The pipeline is pure modular arithmetic with no clock, no random seed, and no network, so the same root, interval, and direction always return the same JSON.
What you send and what you get back
Classic checks include C plus P5 above as G, F# plus M3 above as A#, C4 plus P5 below as F3, and Bb plus m3 above as Db. Wire the free browser form for homework and rehearsal, then call the identical contract from scripts when you need bulk answer keys. Send three required fields. root is a note name: letter A through G, optional accidentals using hash, b, x, double hash, double flat, or the sharp and flat glyphs, and an optional octave integer from zero through nine, for example C, F#, Bb, or C4. Aliases include note, tonic, root_note, and from. interval is a named token from the closed enum: P1, d2, m2, M2, A2, d3, m3, M3, A3, d4, P4, A4, TT, d5, P5, A5, d6, m6, M6, A6, d7, m7, M7, A7, d8, P8, and A8. Aliases include interval_name, name, and iv. direction is above or below (aliases dir, way, side). Missing fields, empty strings, bare numbers used as a root, unrecognized spellings, unknown interval tokens, and directions other than above or below fail with invalid_input naming the field and are not billed. On success the body echoes the root, a parsed letter accidental and pitch class, the canonical interval short code, full interval name, quality, and diatonic number, the normalized direction, the destination note (with octave digits when the root carried an octave), note_name without octave, note_letter, note_accidental, pitch_class, unsigned semitones, signed semitones_directed, method, and formula text for tests. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where a note-from-interval calculator earns its keep
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.
Integration use cases
Ear-training app backends
Score “sing or name the note a minor sixth above this root” with the same diatonic spelling the free browser widget uses.