ForHosting KIT · Developer Utilities

Bolometric magnitude calculator

This bolometric magnitude calculator converts a visual magnitude into a bolometric magnitude using the standard additive correction.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

Enter the measured visual magnitude and the appropriate bolometric correction for the star or source; the calculator returns their sum. It is useful for stellar astronomy work where a visual-band observation must represent radiation across all wavelengths. The calculation is deterministic, accepts finite numeric inputs only, and can be repeated consistently in a browser or through the API.

What bolometric magnitude represents

Visual magnitude describes how bright an astronomical source is in a visual passband, commonly the V band, rather than across the full electromagnetic spectrum. A star can emit substantial energy outside that passband, especially in ultraviolet or infrared wavelengths. Bolometric magnitude is intended to describe the source after accounting for its total radiant output across all wavelengths. The bolometric correction connects those two descriptions. This calculator uses the convention bolometric magnitude = visual magnitude + bolometric correction. You provide both terms in magnitudes, and the result remains a magnitude. Because the astronomical magnitude scale runs backward, a smaller or more negative result represents greater inferred bolometric brightness. The calculator does not estimate a correction from temperature, spectral type, metallicity, extinction, or a model atmosphere. It applies the correction you supply. That distinction matters: selecting an appropriate correction is an astrophysical judgment based on the source and calibration, while adding it is a direct arithmetic operation. Keep the correction convention consistent with the catalog, paper, or model from which you obtained it.

How to enter and interpret the values

Enter the observed visual magnitude in the first field and the bolometric correction in the second. Both entries must be finite numbers; labels, unit strings, blank values, infinity, and other non-numeric inputs are rejected instead of being silently converted. The calculator adds the signed correction exactly as entered. For example, a negative correction makes the bolometric magnitude numerically smaller than the visual magnitude, while a positive correction makes it larger. Do not change the sign merely because the word correction suggests subtraction. In the convention used here, the sign is already part of the correction and the operation is addition. The output is named bolometric_magnitude so it can be used directly in a data pipeline without guessing which quantity was returned. Magnitudes are logarithmic and dimensionless, so the output has no physical unit such as watts. Any uncertainty in the visual measurement or correction is also outside this calculation. If you need an uncertainty for the result, propagate the input uncertainties according to whether they are independent or correlated rather than treating this single value as an error estimate.

Choosing a correction and avoiding common mistakes

The quality of the result depends on the bolometric correction you choose. Corrections may be calibrated for a particular photometric system, filter response, effective temperature range, surface gravity, metallicity, extinction treatment, and adopted solar zero point. Record that provenance beside the calculated magnitude so another researcher can reproduce the value. Before combining a visual magnitude with a correction, confirm that both use compatible definitions and that any required extinction adjustment has been handled consistently. A common mistake is to mix an apparent visual magnitude with a correction intended for a differently calibrated absolute-magnitude relation without documenting the context. The addition itself can still produce a number, but the scientific interpretation may be wrong. Another mistake is reversing the formula and subtracting a negative correction, which changes the result in the opposite direction. This tool deliberately performs only the stated additive relation, making it suitable for spreadsheets, teaching examples, catalog preparation, and automated workflows where the correction is already known. Browser use is free, while an API request costs $0.002; both paths run the same deterministic calculation and require no network lookup.

What you can do with it

Prepare a stellar catalog

Apply an already selected bolometric correction to each visual magnitude before deriving or comparing total luminosity-related quantities.

Check an astronomy calculation

Verify the sign and arithmetic of a published or classroom example using the explicit additive convention.

Automate a reduction workflow

Convert validated visual magnitudes and model-supplied corrections into consistently named bolometric-magnitude results.

FAQ

What formula does the calculator use?

It uses bolometric magnitude = visual magnitude + bolometric correction. The correction is added with its supplied sign.

Should I subtract a negative bolometric correction?

No. Enter the signed correction and add it. A negative correction therefore lowers the numerical magnitude.

Does the calculator determine the correction from spectral type or temperature?

No. You must supply a correction appropriate to the source, filter system, and calibration you are using.

Can I enter text or values with units?

No. Both inputs must be finite numeric values. Unit labels and other non-numeric content produce an invalid-input error.

What does one API calculation cost?

Each API request costs $0.002. The same deterministic calculation is also available free in the browser.

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

POSThttps://api.kit.forhosting.com/astro/bolometric-magnitude

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/astro/bolometric-magnitude \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"visual_magnitude":4.83,"bolometric_correction":-0.07}'

const res = await fetch("https://api.kit.forhosting.com/astro/bolometric-magnitude", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "visual_magnitude": 4.83,
    "bolometric_correction": -0.07
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/astro/bolometric-magnitude",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "visual_magnitude": 4.83,
    "bolometric_correction": -0.07
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/astro/bolometric-magnitude", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"visual_magnitude":4.83,"bolometric_correction":-0.07}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"visual_magnitude":4.83,"bolometric_correction":-0.07}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/astro/bolometric-magnitude", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "visual_magnitude": 4.83,
  "bolometric_correction": -0.07
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "astro.bolometric_magnitude",
  "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

Per request$0.002

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.

Read the full KIT documentation →