ForHosting KIT · Developer Utilities

Schwarzschild radius calculator

This Schwarzschild radius calculator returns the event-horizon radius of a non-rotating black hole from a single mass value.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

The closed form is fully deterministic: Rs equals two times G times M over c squared, using the CODATA 2018 gravitational constant G equals 6.67430 times ten to the minus eleven cubic metres per kilogram per second squared and the exact SI speed of light c equals 299792458 metres per second. With mass in kilograms the result is in metres, the natural SI length for comparing stellar, planetary, and supermassive horizons. Well-known checks include a solar-scale mass near 1.9885 times ten to the thirty kilograms, which yields about 2.95 kilometres, and an Earth-scale mass near 5.972 times ten to the twenty-four kilograms, which yields about 8.87 millimetres. The engine uses only finite arithmetic with no network calls, no sampling, and no date-dependent shortcuts. Use it free in the browser for homework, astrophysics demos, and contest drills, or call the API at $0.002 per successful request when you need reproducible horizon fixtures in CI, teaching software, or science pipelines.

How to use it

Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.

Check your inputs

Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.

Use it again or automate it

Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.

What you can do with it

Get an answer now

Enter one set of values and see the result without building a spreadsheet or script.

Compare scenarios

Change one value at a time and rerun the calculation to understand what affects the result.

Automate repeated work

Use the API when the same calculation needs to run inside your product or workflow.

FAQ

How do I use this capability?

Complete the fields above and run it on this page. The form highlights anything that needs attention.

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/schwarzschild-radius

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/schwarzschild-radius \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"mass":1.9885e+30}'

const res = await fetch("https://api.kit.forhosting.com/astro/schwarzschild-radius", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "mass": 1.9885e+30
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/astro/schwarzschild-radius",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "mass": 1.9885e+30
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/astro/schwarzschild-radius", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"mass":1.9885e+30}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"mass":1.9885e+30}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/astro/schwarzschild-radius", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "mass": 1.9885e+30
}

Example response

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

Limits

max_abs_mass 1e+40

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 →

Run — free