Fahrenheit to Celsius converter
Turn a US weather, thermostat or oven reading in Fahrenheit into Celsius with the exact formula: 32 °F is 0 °C and 212 °F is 100 °C, without the subtract-30-and-halve shortcut. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- F
- 32
- Result
- 0 C
- Converted
- 0
- Fahrenheit
- 32
- Celsius
- 0
A Fahrenheit-to-Celsius converter turns a familiar US weather or oven reading into the metric degree people use in science class, travel apps, and most of the world outside the United States. Approximate mental shortcuts such as subtract thirty and halve are rejected in favour of the exact linear map aligned to the freezing and boiling points of water, so homework checks and sensor pipelines match reference tables.
Why Fahrenheit and Celsius meet at (F − 32) × 5/9
Degrees Fahrenheit remain standard for everyday weather reports, home thermostats, and many cooking instructions in the United States. Degrees Celsius are the SI-compatible everyday scale used in laboratories, international forecasts, and school science almost everywhere else. Both scales are linear and fixed by the same physical anchors: pure water freezes at thirty-two Fahrenheit or zero Celsius and boils at two hundred twelve Fahrenheit or one hundred Celsius at standard pressure.
That means a one-hundred-eighty-degree Fahrenheit span equals a one-hundred-degree Celsius span, so each Fahrenheit degree is exactly five ninths of a Celsius degree. Shifting the zero first—subtract thirty-two—then scaling by five ninths yields the exact map Celsius equals open parenthesis Fahrenheit minus thirty-two close parenthesis times five ninths. Teachers still sometimes teach subtract thirty and half as a rough estimate, but that shortcut drifts by several degrees on body temperature and double digits on oven settings.
Practical tips, checks, and related searches
Prefer sending bare numbers when you control the client; string numbers are accepted only when they match a strict finite numeric pattern without degree symbols, unit letters, thousand separators, or currency marks. Round-trip sanity checks are easy: convert the textbook freezing point thirty-two Fahrenheit and confirm you receive exactly zero Celsius after rounding, convert two hundred twelve and confirm one hundred Celsius, or convert ninety-eight point six body-temperature style readings and compare against a hand calculation of open parenthesis F minus thirty-two close parenthesis times five ninths.
When teaching, pair the exact path with the mental shortcut so students see how many degrees the estimate drifts on oven and fever ranges. Stay inside the absolute range so the linear map cannot overflow into a non-finite result the solver must reject. This landing targets people searching for fahrenheit to celsius, convert F to C, or an exact five ninths temperature calculator; it is not a general multi-scale temperature hub, not a Celsius-to-Fahrenheit primary form, and not a gas-mark or Kelvin converter.
Prefer this capability when the input is already in Fahrenheit and you only need Celsius; if you must convert among many temperature units in one call, use a broader unit converter instead.
What you can do with it
Travel and weather localization
Turn US forecast Fahrenheit highs into Celsius for international itineraries, guest apps, and bilingual weather widgets with the same exact 5/9 factor every reading.
Homework and lab report checks
Students convert classroom Fahrenheit thermometer readings to Celsius and compare hand work against deterministic steps before submitting worksheets.
Cooking and appliance setpoints
Home cooks and recipe importers map oven and candy-thermometer Fahrenheit targets to Celsius setpoints without mental shortcuts that miss by several degrees.
FAQ
What formula converts Fahrenheit to Celsius?
Celsius = (Fahrenheit − 32) × 5/9. The 5/9 factor is exact because a 180 °F span between freezing and boiling equals a 100 °C span.
Is 5/9 exact or approximate?
Exact. This tool uses the standard linear map aligned to water’s freezing and boiling points, not a rough “subtract 30 and half” estimate.
Can I convert Celsius back to Fahrenheit?
This capability is Fahrenheit → Celsius only. Use F = C × 9/5 + 32 on your side, or a bidirectional temperature converter for other scales.
Is the Fahrenheit to Celsius converter free?
The browser tool is free and runs locally.
Why not just subtract 30 and halve?
Because that shortcut drifts by several degrees on a body temperature and by more than ten degrees on oven settings. The converter always subtracts 32 first and then multiplies by 5/9.
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/fahrenheit-to-celsius \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"f":32}'const res = await fetch("https://api.kit.forhosting.com/conv/fahrenheit-to-celsius", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"f": 32
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/fahrenheit-to-celsius",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"f": 32
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/fahrenheit-to-celsius", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"f":32}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"f":32}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/fahrenheit-to-celsius", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"f": 32
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.fahrenheit_to_celsius",
"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 | 1000000000000 |
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
Invalid or missing input fails with a clear invalid_input error instead of inventing a number.
How to call the API and what comes back
Absolute values must stay within the published limit of one trillion. Send a JSON body with one required finite number field named f. Aliases fahrenheit, F, temp_f, value, and temperature are accepted so SDK clients and form posts can use the name that fits the product. On success the response echoes rounded f and fahrenheit, sets celsius, result, and converted to the same rounded Celsius magnitude, unit to the token C, from_unit to F and to_unit to C, factor to the rounded five ninths scale, formula to the string celsius equals open parenthesis f minus thirty-two close parenthesis times five ninths, message to a short English summary, and steps to an ordered array of substitution lines that show the freezing-point offset and the multiply. Failed validation—missing fields, non-finite numbers, bare plus or minus signs, non-numeric strings, values outside absolute limits, or a non-finite converted result—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, checks, and related searches
Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately omit f or pass text.
Technical questions
What happens on missing or non-numeric input?
The API returns invalid_input naming the problem (for example a missing f field). Failed tasks are not charged.