Speed converter
10 m/s is 36 km/h. Convert a speed between metres per second, kilometres per hour, miles per hour, knots and feet per second for road limits, sailing logs, wind specs and homework. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 10
- From
- m/s
- To
- km/h
- Result
- 36 km/h
- Converted
- 36
- Value ms
- 10
- Factor
- 3.6
A speed converter turns one velocity magnitude into another unit without spreadsheet formulas or mental factor tables. Enter a finite value plus a source unit and a target unit among metres per second, kilometres per hour, miles per hour, knots, and feet per second; the tool returns the converted speed, the SI intermediate in m/s, the exact unit factor applied, and step-by-step substitution lines you can paste into a report. Drivers comparing posted limits, sailors reading log books in knots, engineers checking wind or vehicle specs, and students converting homework values all need the same deterministic path.
Which speed units are supported and how conversion works
This capability converts among five everyday speed units that dominate road, rail, marine, aviation training, and laboratory work. Metres per second (m/s) is the SI coherent unit and the internal hub: every conversion multiplies the input by how many metres per second equal one source unit, then divides by how many metres per second equal one target unit. Kilometres per hour use the exact ratio one thousand metres over three thousand six hundred seconds.
Miles per hour use the international statute mile of one thousand six hundred nine point three four four metres per hour. Knots use the international nautical mile of one thousand eight hundred fifty-two metres per hour—the definition adopted for charts and AIS reports. Feet per second use the international foot of zero point three zero four eight metres.
Same-unit requests succeed and return the input magnitude with a short message that no change of unit was required.
Practical tips, limits, and when to use this landing
Prefer sending bare numbers for value when you control the client; string numbers are accepted only when they match a strict finite numeric pattern without currency symbols or thousand separators. Round-trip checks are straightforward: convert A to B and B back to A and confirm you recover the original within the published twelve-decimal rounding.
When teaching unit analysis, pair classic examples such as ten metres per second to thirty-six kilometres per hour, sixty miles per hour to roughly ninety-six point five six kilometres per hour, and one knot to about one point eight five two kilometres per hour. Stay inside the absolute range so intermediate metres-per-second values cannot overflow.
This landing targets people searching for a speed converter, km/h to mph, m/s to ft/s, or knots to kilometres per hour online; it is not a general length-weight-temperature unit converter, not an acceleration calculator, and not a fuel-economy mpg tool.
What you can do with it
Road and traffic limit comparisons
Map apps and rental-car dashboards convert posted km/h limits to mph (or the reverse) so drivers see familiar numbers without manual factor tables.
Marine and aviation log entries
Crews convert knot readings from logs and AIS into km/h or m/s for shore reports, training simulators, and mixed-unit operational briefings.
Lab and homework velocity checks
Students and technicians convert m/s experiment results to km/h or ft/s and compare deterministic steps against hand calculations before submission.
FAQ
How is a knot defined here?
One knot is one international nautical mile per hour, using exactly 1852 metres for the nautical mile, converted through SI m/s.
Is the speed converter free?
The browser tool is free and runs locally.
How many km/h is 60 mph?
About 96.56 km/h. The converter uses the international mile of 1609.344 metres, so the result matches road signs and car dashboards rather than a rounded rule of thumb.
Can I enter a negative speed?
Yes. Negative values are accepted for directed velocities, such as motion against a chosen direction, and they convert with exactly the same factors as positive ones.
Which speed units can I convert?
Five: metres per second, kilometres per hour, miles per hour, knots and feet per second. Any of them can be the starting unit or the target, and a round trip returns your original value.
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/speed \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":10,"from":"m/s","to":"km/h"}'const res = await fetch("https://api.kit.forhosting.com/conv/speed", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 10,
"from": "m/s",
"to": "km/h"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/speed",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 10,
"from": "m/s",
"to": "km/h"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/speed", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":10,"from":"m/s","to":"km/h"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":10,"from":"m/s","to":"km/h"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/speed", 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": 10,
"from": "m/s",
"to": "km/h"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.speed",
"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
Unknown unit names fail with a clear invalid_input error instead of silent wrong factors.
Which speed units are supported and how conversion works
Common aliases are accepted case-insensitively: kmh and kph for km/h, mi/h and miles per hour for mph, kn kt kts and knots for kn, fps and feet per second for ft/s, and mps or metres per second for m/s. If the name is not on that list the solver rejects the request with invalid_input naming the bad field and listing supported units, so clients never guess whether a typo produced a wrong number. Negative speeds are allowed for directed velocity contexts; absolute magnitude must stay within the published one-trillion limit so intermediate products remain finite in IEEE double precision on the Worker and in the browser.
How to call the API and read the response
Value must be a finite number or a strict numeric string within absolute limits of one trillion. Wire this into dashboards, mobile clients, or batch jobs that already hold a speed reading and only need a second unit for display or regulatory comparison without shipping floating conversion tables in every app binary. Send a JSON body with three required fields: value (aliases speed, amount, and v), from (aliases from_unit, unit_from, and source), and to (aliases to_unit, unit_to, and target). From and to must resolve to supported unit names after alias normalization. On success the response echoes the rounded input value, canonical from and to labels, result and converted set to the same rounded target magnitude, value_ms as the SI intermediate, unit as the target label, factor as from-to multiplier, formula as the short equation string, message as an English summary, steps as ordered substitution lines, and supported_units as the five canonical identifiers. Failed validation—missing fields, non-finite numbers, values outside absolute limits, or an unknown unit name—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, limits, and when to use this landing
Normalize display labels on your side if you need locale-specific spellings—this API always returns the short canonical tokens m/s, km/h, mph, kn, and ft/s so automated tests stay stable. Prefer this capability when both endpoints are among the five supported speed units and you need deterministic factors and step strings; if you only need to reformat a number for a locale without changing physical unit, use a number-format capability instead. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when clients deliberately probe unknown unit names.
Technical questions
Which speed units can I convert?
Metres per second (m/s), kilometres per hour (km/h), miles per hour (mph), knots (kn), and feet per second (ft/s), including common aliases such as kph, kt, and fps.
What happens if I send an unknown unit name?
The API returns invalid_input, names the bad field, and lists the supported units. The failed task is not charged.
Are results deterministic across browser and API?
Yes. Handler and widget share the same lib.js solve path with fixed conversion factors and twelve-decimal rounding, so golden examples match production.