Decimal to octal converter
64 in decimal is 100 in octal, because eight times eight is sixty-four: enter a whole number and get its base-8 digits, with negative numbers keeping their minus sign. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- N
- 64
- Decimal
- 64
- Octal
- 100
- Base from
- 10
- Base to
- 8
Octal notation writes whole numbers with eight digit symbols from zero through seven, so each place value is a power of eight instead of a power of ten. Students, embedded developers, and legacy system maintainers still convert decimal integers into octal when reading permission masks, interpreting older machine words, checking textbook exercises, or documenting constants that appear as base-eight literals in C-family languages. This decimal to octal converter accepts a whole number, rejects non-integer input with a clear invalid input error, and returns a deterministic base-8 digit string plus structured fields you can pin in tests.
What decimal-to-octal conversion means and which inputs are valid
A decimal integer is a whole number written with digits zero through nine under place values that are powers of ten. An octal integer uses only digits zero through seven under place values that are powers of eight. Converting from decimal to octal does not change the mathematical value of the number; it only changes how the same magnitude is written.
The classic algorithm repeatedly divides the absolute value by eight, records each remainder as the next least significant octal digit, and stops when the quotient becomes zero. Zero maps to a single octal zero. Negative whole numbers keep a leading minus on the octal magnitude so the sign is preserved without inventing a separate two’s-complement mode.
Digit strings may be large within the published length limit so classroom examples and script-generated constants stay exact through BigInt arithmetic.
Reading the result and checking it by hand
Quick checks help build trust: decimal sixty-four is octal one zero zero because eight squared equals sixty-four; decimal eight is octal one zero; decimal seven is octal seven; decimal zero is octal zero; decimal negative ten is octal negative one two. Use octal alone when a human or report needs a single line; use the full object when automated graders must assert bases and method labels as well as the digit string.
Because remainders are computed with exact integer division, results never drift the way floating-point logarithms would for large inputs.
What you can do with it
Embedded and legacy tooling notes
Developers documenting constants, permission examples, or older word sizes generate stable octal strings from decimal source values without hand-computing remainders.
FAQ
How do I convert a decimal number to octal with this tool?
The response octal field is the base-8 digit string (100 for 64).
Are negative integers supported?
Yes. The absolute value is converted by repeated division by eight, and a leading minus is kept on the octal string when the input is negative and non-zero.
Is the decimal to octal converter free?
The browser tool runs free on your device.
Does the octal result include a 0o or leading-zero C prefix?
No. The octal field is a plain digit string (optional leading minus) so you can add language-specific prefixes yourself when generating code.
What is 64 in octal?
64 is 100 in octal, because eight times eight is sixty-four: the 1 sits in the sixty-fours place and both lower places are zero. Likewise, 8 becomes 10.
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/fmt/decimal-octal \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"n":64}'const res = await fetch("https://api.kit.forhosting.com/fmt/decimal-octal", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"n": 64
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/fmt/decimal-octal",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"n": 64
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/fmt/decimal-octal", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"n":64}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"n":64}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/fmt/decimal-octal", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"n": 64
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "fmt.decimal_octal",
"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
What decimal-to-octal conversion means and which inputs are valid
Send the required field n as a JSON integer or as an integer digit string; aliases value and decimal are accepted when your client already uses those names. Floating-point values, scientific notation, empty strings, and mixed text fail with invalid_input because this product promises a whole-number conversion, not an approximation. Identical inputs always produce identical JSON: there is no network call, random seed, or wall clock in the path.
Reading the response fields and checking common results by hand
On success the response echoes decimal as the parsed whole number when it fits a safe JSON integer, or as a decimal digit string when the magnitude is larger. The octal field is the base-8 digit string you typically want for display, homework answers, and config snippets; it never includes a 0o prefix so you can add language-specific syntax yourself. base_from is always ten and base_to is always eight so downstream code can log the conversion direction without guessing. method is always repeated_division, documenting the algorithm used for the magnitude. Missing n, non-integer n, oversized digit strings, and malformed strings all fail with invalid_input and are not charged after validation rejects the request.
API usage, pricing, classroom workflows, and practical limits
Call the free in-browser decimal to octal converter for homework checks, lecture demos, and quick verification without installing a computer-algebra system or writing a throwaway script. Prefer classroom-scale integers for graded oracles, and keep digit length inside the published cap for isolate safety. Authors shipping SDKs can map the octal string directly into UI labels, CLI flags, or generated code comments that show the base-eight form next to the original decimal constant. Send a JSON body with the required whole integer n, or use the aliases value or decimal if your form or SDK already labels the field that way. Use the prepaid API when a tutoring platform, coding-assessment sandbox, documentation generator, or firmware toolchain needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance. Pair this endpoint with binary or hexadecimal tools when a lesson walks through several bases, or with permission-mask explainers when students map rwx triples to octal modes after they understand pure integer conversion.
Integration use cases
Homework and exam verification
Students convert whole decimal numbers to octal, compare digit strings term by term, and receive a clear invalid_input error when a non-integer is submitted by mistake.
Tutoring platforms and auto-graders
Lesson builders and coding sandboxes call a prepaid JSON contract to check decimal-to-octal answers at scale without reimplementing BigInt division in every stack.
Technical questions
What happens if I enter a non-integer?
The request fails with invalid_input. This converter accepts whole numbers only; floats, scientific notation, and mixed text are rejected and not charged.