CGS system of units converter
1.5 metres is 150 centimetres in the CGS system. Choose length, mass or time, enter the SI value and read the figure in centimetres, grams or seconds with its exact factor of 100, 1000 or 1, so no scale slip reaches your notebook. Free in your browser.
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Worked example
- Value
- 1.5
- Quantity
- Length
- Result
- 150
- Si unit
- m
- Si name
- metre
- Cgs unit
- cm
The centimetre-gram-second system of units, abbreviated CGS, is the classical mechanical system that still appears in electromagnetism textbooks, older laboratory notebooks, and many astrophysics papers. SI measures length in metres, mass in kilograms, and time in seconds; CGS measures the same three quantities in centimetres, grams, and seconds. This converter accepts a finite SI value together with a quantity of length, mass, or time and returns the CGS magnitude with its CGS unit. Metres scale by one hundred, kilograms scale by one thousand, and seconds are unchanged because time is shared.
The three mechanical bases and the exact SI-to-CGS factors
The CGS system of units is defined by three mechanical bases: the centimetre for length, the gram for mass, and the second for time. Those bases sit next to the SI metre, kilogram, and second as pure scale changes, which is why a dedicated SI-to-CGS converter for length, mass, and time is a different search from a general unit toolbox that mixes imperial length, avoirdupois mass, and calendar time. One metre contains exactly one hundred centimetres, so an SI length becomes a CGS length by multiplication by one hundred.
One kilogram contains exactly one thousand grams, so an SI mass becomes a CGS mass by multiplication by one thousand. The second is the same unit in both systems, so an SI duration is already a CGS duration and the factor is one. Those three identities are exact by definition of the prefixes centi and kilo; they are not experimental constants and they do not depend on temperature, local gravity, or a commodity pound.
If you need those, use a converter whose landing is actually about that quantity. Here the contract is mechanical bases only: declare the quantity, send the SI number, and read back the CGS number with its CGS unit so a notebook never hides a factor of one hundred or one thousand.
Where an SI-to-CGS mechanical converter earns its keep
Classrooms teaching unit systems still contrast metre-kilogram-second and centimetre-gram-second in the first weeks of a physics sequence, and students lose marks by writing two kilograms as two grams or by leaving a length in metres inside a CGS formula that expects centimetres. A deterministic SI-to-CGS converter for the three mechanical bases lets a tutoring site, a learning-management plugin, or a problem generator check the scale without pulling a computer-algebra library.
Laboratory information systems that ingest mixed historical records often store lengths in metres from modern instruments and centimetres from older CGS glassware; converting at the boundary with an explicit quantity field is safer than inferring the system from a unit suffix that someone omitted. Astronomy and plasma-physics notebooks still quote CGS densities and scale heights beside SI constants; converting the mechanical inputs in one call keeps the notebook from hiding a factor of one hundred or one thousand inside a later electromagnetic formula.
Keep requests small, pin the rounded result in tests, and you get reproducible centimetre, gram, and second values without standing up a general units package of your own.
What you can do with it
Physics homework and LMS checks
Let students convert an SI length, mass, or time to CGS and verify centimetres, grams, or seconds against the textbook scale factors.
Laboratory records that mix SI and CGS
Normalise metres, kilograms, and seconds from modern instruments to centimetres, grams, and seconds used in older CGS glassware logs.
Astronomy and plasma notebooks
Convert mechanical SI inputs to CGS before a later Gaussian formula so a hidden 100× or 1000× factor does not leak into density or scale height.
FAQ
How do I convert SI units to the CGS system of units?
Send a finite SI value and a quantity of length, mass, or time.
Which quantities does the CGS system of units converter support?
Only the three mechanical bases: length (metre to centimetre), mass (kilogram to gram), and time (second to second). Energy, force, pressure, and electromagnetic CGS variants are out of scope.
Why is time the same in SI and CGS?
Both systems use the second as the time base. The converter still accepts quantity time so a script can treat all three mechanical bases through one contract without a special case in the client.
What happens if the unit type is unsupported or the value is not a number?
Unsupported quantities such as energy, and values that are missing, NaN, or Infinity, are rejected and are not billed.
Can it convert newtons to dynes or joules to ergs?
No. It handles only the three base quantities: length, mass and time. Force, energy, pressure and electromagnetic units need their own conversions, above all the electromagnetic ones, whose CGS and SI forms differ by more than a power of ten.
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/cgs-system-of-units \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1.5,"quantity":"length"}'const res = await fetch("https://api.kit.forhosting.com/conv/cgs-system-of-units", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1.5,
"quantity": "length"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/cgs-system-of-units",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1.5,
"quantity": "length"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/cgs-system-of-units", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1.5,"quantity":"length"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1.5,"quantity":"length"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/cgs-system-of-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": 1.5,
"quantity": "length"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.cgs_system_of_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
Unsupported quantities and values that are not finite numbers fail with invalid_input so a pipeline never silently treats energy as mass or a blank field as zero.
The three mechanical bases and the exact SI-to-CGS factors
This endpoint applies only those identities. It will not convert force from newton to dyne, energy from joule to erg, pressure from pascal to barye, or electromagnetic quantities whose Gaussian and SI forms differ by powers of four pi and by the speed of light.
Input contract, response shape, and error behaviour
Negative values are allowed because a signed displacement or a mass-change delta can be negative even though a laboratory mass is usually positive; the converter does not invent a positivity constraint that a scale factor does not need. quantity is a closed enumeration: length, mass, or time. On success the body echoes value and quantity, names the SI unit as metre, kilogram, or second, and returns result as the CGS magnitude together with the CGS unit centimetre, gram, or second, the exact factor, and a one-line formula of the form CGS equals SI times factor. A length of one point five therefore yields one hundred fifty centimetres; a mass of two yields two thousand grams; a time of sixty yields sixty seconds. Failed validation is not billed. Send a JSON object with two required fields. value is the SI magnitude: a finite JSON number or a numeric string. Missing, empty, NaN, and Infinity values are not numbers for this contract and fail with invalid_input naming value. The form renders a select so you do not have to memorise spellings; the API still rejects any other string as an unsupported unit type, including energy, force, temperature, and free-text unit symbols such as centimetre or kilogram.
Technical questions
What does the CGS system of units converter cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.