Sig fig calculator
1234.567 rounded to 3 significant figures is 1230, written 1.23 × 10³ in scientific form. Enter a number and how many meaningful digits to keep, from 1 to 15; halves move away from zero, so 1.25 becomes 1.3. Free in your browser.
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Run — free
Worked example
- Value
- 1,234.567
- Figures
- 3
- Rounded
- 1,230
- Scientific
- 1.23e+3
People type sig fig when they need a number rounded to a fixed count of meaningful digits, not when they want a general decimal-place tool. Lab reports, chemistry stoichiometry, physics estimates, and homework checkers all demand three or four significant figures rather than a calculator dump of twelve noisy places.
What a sig fig is and how this calculator rounds
A sig fig, short for significant figure, is a digit that carries meaning in a measured or computed quantity. Counting starts at the first non-zero digit and includes zeros that sit between non-zero digits or that were retained by an explicit rounding choice. Leading zeros after a decimal point do not count, which is why zero point zero zero one two three four has four significant figures in the digits one two three four, not six.
Rounding to N sig figs therefore keeps the leading N meaningful digits and replaces the rest according to a fixed half-away-from-zero rule, rather than chopping a fixed number of decimal places. That distinction is the whole reason this landing exists: two decimal places on one thousand two hundred thirty-four point five six seven still leaves a long integer part, while three significant figures compresses the whole magnitude to one thousand two hundred thirty.
Halfway cases move away from zero, so one point two five to two figures becomes one point three and negative one point two five becomes negative one point three. Zero stays zero.
Where a sig fig calculator earns its keep
Classrooms and tutoring platforms use a dedicated sig fig calculator so learners can check significant-figure homework without flipping a general rounding page through extra modes or decimal-place settings. Exam-prep generators need a deterministic oracle that marks one point two five to two figures as one point three under a published halfway rule instead of depending on a language Math.round quirk.
Chemistry and physics labs keep measured values honest when an instrument only supports three meaningful digits, and engineering notebooks snap intermediate results so they do not pretend to more precision than the data support. Failed validation does not consume balance. Keep requests small, pin rounded and the scientific string in tests, and you get reproducible sig-fig snaps for teaching, grading, reporting, and edge workers without standing up a computer-algebra stack of your own.
Distinct search intent from a multi-mode decimal rounding tool and from the longer significant-figures-rounder phrasing: this landing answers the abbreviated classroom query that people actually type.
What you can do with it
Lab reports and homework
Round a measured or calculated value to the required sig-fig count for chemistry, physics, and engineering write-ups without inventing extra digits.
FAQ
How do I round a number to N sig figs?
Send a finite value and a positive integer figures count from 1 to 15.
Does 1.25 to two significant figures become 1.2 or 1.3?
It becomes 1.3. Halfway cases use half-away-from-zero, so 1.25 rounds to 1.3 and −1.25 rounds to −1.3.
Are leading zeros after the decimal significant?
No. In 0.001234 the leading zeros after the decimal do not count. Two sig figs on that value yield 0.0012, not 0.00.
What happens if figures is zero or not an integer?
The figure count must be a positive integer; a count below one or a non-integer is not a valid sig-fig request and is not billed.
How is this different from rounding to decimal places?
Decimal places count only the digits after the point, while significant figures count from the first meaningful digit. Two decimal places leave 1234.567 long; three significant figures turn it into 1230.
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/math/sig-fig \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1234.567,"figures":3}'const res = await fetch("https://api.kit.forhosting.com/math/sig-fig", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1234.567,
"figures": 3
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/math/sig-fig",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1234.567,
"figures": 3
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/math/sig-fig", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1234.567,"figures":3}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1234.567,"figures":3}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/math/sig-fig", 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": 1234.567,
"figures": 3
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "math.sig_fig",
"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.
Limits
max_abs_value | 1e+300 |
max_figures | 15 |
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
This endpoint accepts one finite number and a positive integer figure count, then returns the value rounded to that many significant figures with a published half-away-from-zero rule. Non-finite values and figure counts that are not positive integers fail with invalid_input and are not charged.
What a sig fig is and how this calculator rounds
The response echoes the parsed value and the requested figure count, returns rounded as the primary result, adds a scientific-style display string built with the same figure count, and includes a method tag, a short formula, and a one-line message. There is no computer-algebra path and no sampling: the engine either builds a finite result inside the supported magnitude range or rejects the input with invalid_input.
Input contract, response shape, and error behaviour
A figure count of zero, a negative integer, or a non-integer such as one point five also fails, because the count is not a positive integer. Magnitude is capped so the absolute value stays at most one times ten to the three hundred; larger figures overflow the reliable range of the floating-point path and are rejected rather than silently corrupted. Example: value one thousand two hundred thirty-four point five six seven with figures three yields rounded one thousand two hundred thirty and scientific one point two three times ten to the three. Example: value zero point zero zero one two three four with figures two yields rounded zero point zero zero one two. POST a JSON body with two required fields: value, the finite number to round, and figures, the positive integer count of significant figures to keep. Value may arrive as a JSON number or as a numeric string; aliases n, number, x, amount, input, and text are accepted when value is omitted. Figures must be an integer from one through fifteen; aliases sig_figs, sigfigs, n_figures, digits, sf, and count are accepted when figures is omitted. Missing fields, empty strings, non-numeric text, NaN, and Infinity fail with invalid_input naming the field and are not billed. On success the body echoes the cleaned value and the figure count, returns rounded as the primary numeric result, lists scientific as a display string with exactly that many significant figures, and includes method set to significant_figures, a short formula string, and a one-line message. Pair the payload with your own labels; this endpoint does not emit plots or multi-step classroom prose beyond the message and formula fields. Keep the request small and pin rounded plus scientific in tests so homework oracles and production pipelines stay reproducible.
Integration use cases
Deterministic test fixtures
Generate reproducible rounded numbers and scientific strings for unit tests, docs, and continuous-integration assertions.
Telemetry and display normalization
Snap sensor readings or API numbers to a published significant-figure count before you show them on a dashboard or in a report.
Technical questions
What does the sig fig calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.