Nuclear cross section converter
Switch a cross section between barns and area units without a handbook: 1 barn is exactly 10⁻²⁸ square meters, 10⁻²⁴ square centimeters or 100 square fermis, and every result passes through square meters. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 1
- Source unit
- barn
- Target unit
- m2
- Result
- 0
- From label
- barn
- To label
- square meter
- Si
- 0
A nuclear cross section converter turns a reaction-area quantity written in one unit into another without hunting handbook tables or rewriting spreadsheet formulas by hand.
Supported units and how the conversion is computed
The converter accepts eight nuclear cross-section families under stable canonical codes: barn for the classic barn (exactly ten to the minus twenty-eight square meters), mb for the millibarn, ub for the microbarn (also written μb), nb for the nanobarn, pb for the picobarn, m2 for the SI square meter, cm2 for the square centimeter, and fm2 for the square fermi (square femtometer).
Factors follow SI and nuclear-data convention: one barn is exactly one times ten to the minus twenty-eight square meters and one times ten to the minus twenty-four square centimeters, which also equals one hundred square fermis; millibarn through picobarn apply the usual metric prefixes on the barn. Because the intermediate is always SI square meters, converting A to B and B to A is consistent up to the published rounding of twelve decimal places, and there is no pairwise matrix that can drift out of sync.
Macroscopic cross sections that mix number density with microscopic area, activity, dose, or fluence alone are intentionally out of scope so reactor physics, particle-data, and lab users get predictable area-only results under one clear convention.
Everyday uses in labs and reactor physics
Use the free in-browser nuclear cross section converter when you need a quick barn to square-meter check, a millibarn to square-centimeter normalization, or a picobarn to square-fermi switch while reading an ENDF plot, reactor physics homework, neutron-transport memo, or detector paper. Open the page, enter the number and units, and copy the result without installing a spreadsheet, a unit library, or a desktop calculator pack. Source inputs follow the same retention rules as other KIT parse items, and results are safe to cache because the algorithm is fully deterministic.
Authors shipping mobile apps or chatbots can map the result and formula fields directly into cards that show both the number and the conversion path students, engineers, and technicians expect on paper.
What you can do with it
Reactor physics and ENDF table checks
Normalize evaluated cross sections between barn and millibarn before comparing library plots, transport inputs, or homework answers under one deterministic contract.
Particle-physics analysis chains
Convert picobarn and nanobarn luminosities and process cross sections to SI square meters for simulation metadata and publication unit tables.
Lab instruments and teaching labs
Students and technicians convert barn to cm² or fm² while reading detector notes, without guessing handbook factors or retyping spreadsheet cells.
FAQ
Which nuclear cross section units does this converter support?
barn (b), mb (millibarn), ub (microbarn), nb (nanobarn), pb (picobarn), m2 (m²), cm2 (cm²), and fm2 (fm²).
How do I convert 1 barn to cm²?
The response result is 1e-24, plus an si intermediate in m² and a readable formula.
What happens if I send an unknown unit?
The message names the field and lists supported units. Validation failures are not charged.
Is the nuclear cross section converter free?
The browser tool runs free on your device.
Will converting back and forth give the same number?
Yes, within the published rounding of twelve decimals. Every conversion passes through square meters, so going from barn to picobarn and back cannot drift the way a table of pairwise factors can.
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/nuclear-cross-section \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1,"from":"barn","to":"m2"}'const res = await fetch("https://api.kit.forhosting.com/conv/nuclear-cross-section", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1,
"from": "barn",
"to": "m2"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/nuclear-cross-section",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1,
"from": "barn",
"to": "m2"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/nuclear-cross-section", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1,"from":"barn","to":"m2"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1,"from":"barn","to":"m2"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/nuclear-cross-section", 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": "barn",
"to": "m2"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.nuclear_cross_section",
"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
The browser tool runs free on your device; the prepaid API charges $0.002 per successful item when pipelines need the same contract from servers and automation.
Supported units and how the conversion is computed
Friendly aliases such as barns, millibarn, microbarn, nanobarn, picobarn, square meters, square centimeters, square fermis, and common symbols like b, m², cm², fm², and μb are normalized so forms and APIs can pass either short codes or full names. Every request multiplies the input value by the exact square-meter factor for the source, then divides by the factor for the target.
Request shape, response fields, and unknown-unit errors
The error message names the bad field and lists the supported set so clients can correct forms without guessing. Negative values are allowed when you need signed residual or delta-sigma workflows; zero converts cleanly to zero in every target unit. Send a JSON body with three required fields: value as a finite number, from as the source unit string, and to as the target unit string. Aliases amount, quantity, and sigma are accepted for value; unit_from and source for from; unit_to and target for to. On success the response echoes the canonical from and to codes, human-readable from_label and to_label strings, the converted result, the intermediate si quantity in square meters with si_unit set to m2, the dimensionless factor from source to target, a short formula line suitable for UI display, the method tag nuclear_cross_section_si, and the fixed list of units_supported. Missing value, non-finite numbers such as NaN or Infinity, missing unit fields, and any token that does not map to a supported unit fail with invalid_input and are not charged after the engine rejects the request. Identical inputs always yield identical JSON because the path is pure arithmetic with no randomness, no remote lookup, and no dependence on the wall clock, which makes the endpoint safe to pin in continuous-integration goldens and SDK contract tests. Extreme magnitude pairs such as picobarn to square meters remain well-defined as long as IEEE double precision can represent the intermediate SI product.
Browser use, API pricing, and everyday workflows
Switch to the prepaid API when a nuclear-data pipeline, Monte Carlo post-processor, laboratory LIMS, particle-physics analysis chain, or education platform must convert cross sections at scale under a stable KIT contract at $0.002 per successful item; validation failures that raise invalid_input do not consume balance after rejection. Pair this endpoint with radiation-exposure or energy converters when a product pipeline needs several nuclear measure families, or call it alone when search traffic is specifically for nuclear cross section conversion—barn, millibarn, microbarn, nanobarn, picobarn, square meters, square centimeters, and square fermis—rather than a general unit switchboard.
Technical questions
How many square meters is one barn?
Exactly 1×10⁻²⁸ m². Send value: 1, from: "barn", to: "m2" to see result 1e-28 (reported with stable twelve-decimal rounding of the SI intermediate path).