Metric to standard converter
100 °C comes out as 212 °F and 1 m as 3.280839895013 ft. Enter a value and its metric unit, from millimetres to tonnes or kelvin, and get the one US customary figure used on labels, weather reports and freight papers. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 1 m
- Result
- 3.280839895 ft
- Converted
- 3.280839895
- From unit
- m
- To unit
- ft
A metric to standard converter turns a length, mass, or temperature written in everyday SI-family units into the United States customary magnitude Americans actually use on labels, weather reports, and freight documents. You send two fields: the numeric value and the metric unit it is measured in. The engine applies an exact published factor — the 1959 international yard and pound for length and mass, and the linear map nine-fifths plus thirty-two for Celsius — then returns a single converted value in inches, feet, miles, ounces, pounds, US short tons, or degrees Fahrenheit. Non-finite values are rejected as well.
US customary counterparts and the exact factors
United States customary units, which searchers often call standard units, are not a renamed copy of the International System. Length still sits on the international inch, foot, yard, and statute mile fixed by the 1959 yard and pound agreement: one inch equals exactly 25.4 millimetres, one foot equals exactly 0.3048 metres, and one mile equals exactly 1609.344 metres.
Mass sits on the avoirdupois pound of exactly 0.45359237 kilograms, with sixteen ounces in a pound and two thousand pounds in a United States short ton, which is not the same object as a metric tonne. Temperature is an affine map rather than a prefix hop.
Fahrenheit places the ice point at 32 degrees and the steam point at 212, so one hundred Celsius degrees span one hundred eighty Fahrenheit degrees; the converter therefore applies F equals C times nine fifths plus 32, and it subtracts 273.15 from kelvin before that same scale.
Input contract, mapping table, and unrecognized units
Unknown tokens, including United States names such as feet or pounds, are not recognized and fail. Each accepted token has exactly one customary target: millimetres and centimetres become inches, metres become feet, kilometres become miles, milligrams and grams become avoirdupois ounces, kilograms become pounds, tonnes become US short tons, and both Celsius and kelvin become degrees Fahrenheit. Kelvin below zero and Celsius below minus 273.15 are rejected because they sit below absolute zero.
Negative lengths and masses are allowed as signed deltas. Failed validation is not billed.
Where a metric to standard converter earns its keep
Classrooms in the United States still assign homework that asks for metres in feet, kilograms in pounds, and Celsius in Fahrenheit, because textbooks and state tests keep both systems in play. A teacher can send value 1 with unit m and expect the exact foot count from the 1959 foot, or value 100 with unit c and expect 212, and an LMS plugin can mark the same items with this deterministic oracle instead of a scraped webpage.
Importers converting carton dimensions printed in centimetres, shipping clerks turning kilogram weights into pounds for a US carrier, and travelers reading a Celsius forecast next to a Fahrenheit thermostat all type the same two-field form. Failed validation does not consume balance. Dedicated SI-to-SI converters remain the right tool when the search is only prefixes, and single-pair converters remain the right tool when the query is metres to feet alone; this landing exists for people who have a metric number and want the United States standard counterpart in one step.
What you can do with it
Classroom dual-system homework
Let students convert 1 m to feet or 100 °C to Fahrenheit and verify the exact 1959 and nine-fifths results against textbook tables.
Import labels and freight quotes
Turn centimetre carton sizes into inches and kilogram shipment weights into pounds for a United States carrier without a general unit library.
Travel weather and thermostat checks
Read a Celsius forecast or kelvin lab reading as Fahrenheit next to a US thermostat using the same two-field form.
FAQ
Which metric units can I convert to US standard?
Length: mm and cm to inches, m to feet, km to miles. Mass: mg and g to ounces, kg to pounds, t (tonne) to US short tons. Temperature: c (Celsius) and k (kelvin) to Fahrenheit.
What happens if the unit is not recognized?
Only the closed metric enum is accepted; US names such as feet or pounds, and any unknown token, are rejected and not billed.
How is one metre converted to feet?
The international foot is exactly 0.3048 metres, so feet = metres ÷ 0.3048. One metre is 3.280839895013 feet at twelve decimal places.
How are Celsius and kelvin converted to Fahrenheit?
F = C × 9/5 + 32. Kelvin is converted by subtracting 273.15 to obtain Celsius, then applying the same map. Values below absolute zero are rejected.
Is a metric tonne converted to a US ton?
Yes, a tonne becomes US short tons, and the two are not the same: a short ton is 2000 pounds of exactly 0.45359237 kg each, while a tonne is 1000 kg.
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/metric-to-standard-converter \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1,"unit":"m"}'const res = await fetch("https://api.kit.forhosting.com/conv/metric-to-standard-converter", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1,
"unit": "m"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/metric-to-standard-converter",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1,
"unit": "m"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/metric-to-standard-converter", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1,"unit":"m"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1,"unit":"m"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/metric-to-standard-converter", 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,
"unit": "m"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.metric_to_standard_converter",
"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
A unit that is not in the recognized metric set fails with invalid_input instead of inventing a number.
US customary counterparts and the exact factors
This endpoint does not hop between millimetres and metres or between grams and kilograms — those SI prefix conversions belong to a metric converter. It maps each recognized metric token onto one customary counterpart and returns that converted value. The factors live in a tiny table so the same request always yields the same JSON, with no network call and no dependence on wall-clock time.
Input contract, mapping table, and unrecognized units
POST a JSON body with two required fields. value is the numeric magnitude and must be a finite number; JSON numbers and numeric strings are accepted, but NaN, Infinity, empty strings, and missing values fail with invalid_input naming the field. unit is the metric source token and is restricted to a closed enum: mm, cm, m, and km for length; mg, g, kg, and t for mass, where t means the metric tonne of one thousand kilograms; c and k for temperature in Celsius and kelvin. On success the body echoes the input value, names from_unit and to_unit, and returns result as the converted magnitude rounded to twelve decimal places for stable goldens. unit repeats the target token so a client can print the number with its unit. formula restates the arithmetic.
Technical questions
What does the metric to standard converter cost?
The browser tool is free. API requests use prepaid balance at $0.002 per successful call; invalid input is not billed.