ForHosting KIT · Developer Utilities

Centrifuge g-force calculator

This centrifuge g-force calculator converts rotor radius and rotational speed into relative centrifugal force, commonly abbreviated RCF and expressed as a multiple of standard gravity.

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Run — free How it works & API

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Enter the distance from the rotor axis to the sample in centimeters and the speed in revolutions per minute. The calculator applies the established laboratory conversion directly, making it useful when a protocol specifies g but a centrifuge controller displays RPM, or when two rotors need to be compared at the same operating speed.

Enter the radius at the sample position

Use the distance from the center of rotation to the location in the tube where the sample experiences the force. Enter that value in centimeters, because the conversion constant used by this calculator is defined for centimeters and revolutions per minute. Rotor documentation may list a minimum, maximum, or average radius. Choose the radius that matches the protocol and the question you are trying to answer. The maximum radius is often used when reporting the greatest RCF at the bottom of a tube, while an average radius may be appropriate for a method explicitly written around that convention. Do not enter the rotor diameter; if a specification gives only diameter, divide it by two first. The calculator rejects a negative radius because radial distance cannot be negative. Zero is accepted and correctly produces zero g, although it usually represents a theoretical point on the rotation axis rather than a practical sample position. Consistent radius measurement is essential when comparing rotors with different geometry.

Understand the RPM-to-RCF calculation

The calculation is RCF = 1.118 × 10⁻⁵ × r × RPM², where r is the rotor radius in centimeters. The result is dimensionless relative force expressed in g units, meaning a result of 10,000 represents ten thousand times standard gravitational acceleration. RPM is squared, so speed has a much stronger effect than radius: doubling the rotational speed multiplies RCF by four, while doubling the radius multiplies RCF by two. This is why copying an RPM setting from one rotor to another can expose samples to a different force even when both machines report the same speed. The calculator uses the entered values directly and does not apply a rotor-specific correction, acceleration ramp, temperature adjustment, or duration model. It provides the instantaneous nominal RCF implied by radius and RPM. Manufacturers may round displayed values, so small differences between this result and an instrument panel can reflect rounding rather than a meaningful physical discrepancy.

Use the result in a reproducible protocol

When documenting a centrifugation step, record the target RCF, the radius convention, the duration, and any temperature or brake settings relevant to the procedure. Reporting only RPM makes a protocol dependent on the rotor that happened to be used, because different radii produce different forces at the same rotational speed. RCF is therefore the better value for transferring a method between laboratories or between instruments. Use this calculator to verify a controller setting, convert a legacy RPM instruction, or compare the nominal force delivered by candidate rotors. Check the centrifuge and rotor manufacturer limits before selecting a speed; a mathematically valid result does not establish that the equipment, tube, adapter, or sample can safely withstand it. The API price is $0.002 per calculation, and the same deterministic formula is suitable for automated worksheets, equipment setup tools, and protocol validation pipelines. Keep the original inputs with the result so another person can reproduce the calculation and confirm which radius was used.

What you can do with it

Convert an RPM-only protocol

Calculate the nominal RCF for a published speed after identifying the sample radius of the rotor in use.

Compare centrifuge rotors

See how two rotor radii produce different g-force values at the same RPM before transferring a procedure.

Validate equipment setup

Add a deterministic RCF check to a worksheet or laboratory workflow that records radius and speed.

FAQ

What formula does the calculator use?

It uses RCF = 1.118 × 10⁻⁵ × radius in centimeters × RPM².

What does the result in g mean?

It is relative centrifugal force as a multiple of standard gravitational acceleration, not acceleration expressed in meters per second squared.

Should I use minimum, average, or maximum rotor radius?

Use the radius convention required by your protocol. Maximum radius describes force near the tube bottom, while some procedures specify an average radius.

Why does RPM have such a large effect?

RPM is squared in the formula, so doubling RPM produces four times the relative centrifugal force at the same radius.

Does a valid calculation mean the speed is safe?

No. Confirm the rated limits of the centrifuge, rotor, adapters, and tubes before operation.

What does an API calculation cost?

Each API request costs $0.002.

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/mech/centrifuge-g-force

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/mech/centrifuge-g-force \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"rotor_radius_cm":10,"rpm":10000}'

const res = await fetch("https://api.kit.forhosting.com/mech/centrifuge-g-force", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "rotor_radius_cm": 10,
    "rpm": 10000
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/mech/centrifuge-g-force",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "rotor_radius_cm": 10,
    "rpm": 10000
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/mech/centrifuge-g-force", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"rotor_radius_cm":10,"rpm":10000}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"rotor_radius_cm":10,"rpm":10000}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/mech/centrifuge-g-force", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "rotor_radius_cm": 10,
  "rpm": 10000
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "mech.centrifuge_g_force",
  "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 →