Solar mass, radius & luminosity converter
One solar mass is 1.98847 × 10³⁰ kg. This converter turns M☉, R☉ and L☉ into kilograms, metres and watts, or into Earth and Jupiter units, for star tables, exoplanet notes and homework. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Numeric quantity to convert
- 1
- Source unit
- Msun
- Target unit
- kg
- Result
- 1,988,470,000,000,000,000,000,000,000,000
- From label
- solar mass
- To label
- kilogram
- Dimension
- mass
Stellar catalogues, exoplanet papers and homework problems quote masses, radii and luminosities in solar units, then ask for the same numbers in SI. This capability converts solar mass M☉, solar radius R☉ and solar luminosity L☉ to kilograms, metres, watts and a short list of related units—grams, kilometres, Earth and Jupiter masses and radii, kilowatts through gigawatts, and erg per second—using published fixed factors including IAU 2015 nominal solar radius and luminosity. Conversions stay inside one physical dimension: mass units only map to mass units, radius to radius, luminosity to luminosity.
Choosing value, from, and to for solar and SI units
Mass family tokens include Msun, solar mass, kg, g, Mearth and Mjupiter. Radius family tokens include Rsun, solar radius, m, km, Rearth and Rjupiter. Luminosity family tokens include Lsun, solar luminosity, W, kW, MW, GW and erg/s.
Value may be negative when you track signed deltas; NaN and Infinity are rejected. One solar mass equals 1.98847 times ten to the thirty kilograms by the fixed conventional factor used here; one solar radius equals 6.957 times ten to the eight metres and one solar luminosity equals 3.828 times ten to the twenty-six watts following IAU 2015 nominal constants. Earth and Jupiter comparison units use the conventional masses and mean radii listed in the product notes so classroom and catalogue workflows stay pin-stable across runs.
What you can do with it
Stellar catalogue and paper prep
Convert published M☉, R☉ and L☉ values into kg, m and W for tables, figure captions and SI-first data products without retyping constants by hand.
Homework and exam verification
Students and graders check solar-to-SI conversions for mass, radius and luminosity and get a clear error when an unknown unit or wrong dimension is submitted.
Exoplanet and pipeline tooling
Scripts normalise host-star and planet comparison units (solar, Earth, Jupiter) to SI intermediates before orbital or transit calculations.
FAQ
How do I convert one solar mass to kilograms?
The result is 1.98847e30 kilograms using the fixed conventional solar-mass factor.
Can I convert solar mass to solar radius?
No. Mass and radius are different physical dimensions.
Which solar constants does this use?
IAU 2015 nominal solar radius (6.957e8 m) and luminosity (3.828e26 W), plus a fixed conventional solar mass of 1.98847e30 kg, documented in the product notes.
Is the solar mass radius converter free?
The browser tool runs free on your device.
How many watts is one solar luminosity?
One solar luminosity is 3.828 × 10²⁶ watts, the IAU 2015 nominal value. From the same entry you can also get kilowatts, megawatts, gigawatts or erg per second.
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/conv/solar-units \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1,"from":"Msun","to":"kg"}'const res = await fetch("https://api.kit.forhosting.com/conv/solar-units", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1,
"from": "Msun",
"to": "kg"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/solar-units",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1,
"from": "Msun",
"to": "kg"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/solar-units", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1,"from":"Msun","to":"kg"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1,"from":"Msun","to":"kg"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/solar-units", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 1,
"from": "Msun",
"to": "kg"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.solar_units",
"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
Unknown unit names and cross-dimension requests fail with a clear invalid_input error and are not charged. The algorithm is pure arithmetic with no network, no random seed and no clock, so identical inputs always yield identical JSON for tests and pipelines.
Choosing value, from, and to for solar and SI units
Send a JSON object with three required fields: value (a finite number, aliases amount and quantity), from (source unit, aliases unit_from and source), and to (target unit, aliases unit_to and target). Unit strings are case-insensitive; spaces, underscores and hyphens collapse to the same alias table, so M_sun, solar-mass and Msun all resolve to solar mass.
Reading the result, SI intermediate, and dimension checks
The result field is the converted quantity in the target unit, rounded to twelve decimal places for stable goldens and UI display. Factor is how many target units equal one source unit at the given scale, and formula restates the multiply-and-divide path for teaching and debug logs. Units_supported lists every canonical token by family. Missing value, from or to fails the same way. On success the response echoes value, from and to with human-readable from_label and to_label, plus dimension set to mass, radius or luminosity. The si field is the intermediate quantity in the SI base for that dimension—kilograms for mass, metres for radius, watts for luminosity—with si_unit naming that base. Method is always solar_units_iau2015 so downstream code can branch without sniffing shapes. If from and to belong to different dimensions—for example Msun to Rsun—the engine raises invalid_input with a dimension mismatch message rather than inventing a nonsense conversion. Unknown tokens raise invalid_input naming the bad unit and listing supported families. Validation failures never consume prepaid balance after the engine rejects the request.
API pricing, browser use, and practical workflows
Call the free in-browser solar mass radius converter for homework checks, lecture demos and quick catalogue spot-checks without installing Astropy or a local constants table. Authors shipping SDKs can map result, si and dimension into UI tables that mirror what students write on paper when they convert one solar mass to kilograms or one solar luminosity to watts by hand. Use the prepaid API when an exoplanet pipeline, stellar isochrone service, tutoring platform or research notebook needs a stable contract under KIT balance at $0.002 per successful item. Pair this endpoint with light-year or orbital calculators when the next step is dynamical modelling rather than unit conversion alone. Keep inputs within ordinary floating-range magnitudes; extreme exponents may lose precision in IEEE double arithmetic the same way any browser calculator would.
Technical questions
What happens with an unknown unit?
The request fails with invalid_input, names the unknown unit, and lists supported mass, radius and luminosity tokens. No balance is charged.