Fuel economy converter
Restate a fuel economy figure on the scale your market uses: 30 US MPG is 7.84048611111 L/100km, 12.7543112229 km/L or 36.0284977651 UK MPG, all shown together. Handy for overseas car listings and fleet reports. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Fuel-economy magnitude to convert
- 30
- Input fuel-economy unit
- mpg_us
- Output fuel-economy unit
- l_100km
- Result
- 7.8404861111
- Mpg us
- 30
- Mpg imp
- 36.0284977651
- Km per l
- 12.7543112229
Fuel economy conversion between United States miles per gallon, imperial UK miles per gallon, kilometers per liter, and liters per 100 kilometers is a daily task for car shoppers comparing overseas listings, fleet managers normalizing telematics feeds, journalists writing for multi-region audiences, and students working mixed-unit physics problems. People search for a fuel economy converter when they need a single figure restated on the scale their market uses, not a general multi-category unit toolbox that also converts length or temperature. Zero and negative values are rejected because fuel economy is undefined for non-positive readings. Unrecognized unit names fail with a clear validation error instead of silently guessing a nearby symbol.
How the fuel economy converter maps MPG, km/L and L/100km through a km/L bridge
Start from kilometers per liter as the coherent intermediate: higher values always mean better economy, which keeps the arithmetic simple for miles-per-gallon families and for the inverted liters-per-100-kilometers scale. One international mile is exactly one point six zero nine three four four kilometers. One United States liquid gallon is exactly three point seven eight five four one one seven eight four liters, so US MPG multiplies by one point six zero nine three four four divided by that gallon volume to reach kilometers per liter.
One imperial UK gallon is exactly four point five four six zero nine liters, so imperial MPG multiplies by the same mile factor divided by the larger gallon and therefore yields a higher MPG number for the same car. Liters per 100 kilometers measure consumption rather than economy: convert by taking one hundred divided by the L/100km figure to obtain km/L, then reverse that relation when the target unit is L/100km. This calculator never mixes those paths ad hoc.
It multiplies or inverts the input amount into km/L using the source unit factor, then multiplies or inverts again for the target unit. Because every path shares the same intermediate, converting thirty US MPG to L/100km and back, or comparing UK brochure MPG with metric fleet logs, stays numerically consistent within ordinary floating-point precision. The tool does not convert miles per liter, does not invent hybrid units, does not fetch live fuel prices or CO2 tables, and does not estimate real-world driving.
It answers only the algebraic fuel-economy unit conversion people mean when they type fuel economy converter into a search bar and expect MPG US, MPG imperial, km/L, and L/100km.
Where dedicated fuel economy conversion shows up in real work
Automotive marketplaces and importer listings constantly restate manufacturer figures from US EPA MPG or UK imperial MPG into L/100km or km/L so shoppers in another region can compare cars without a spreadsheet. Fleet and logistics teams normalize telematics exports that mix US dashboards, European OBD logs, and Asian km/L reports into one warehouse column before computing cost per kilometer. Journalism and review sites publish the same test loop in MPG for North America and L/100km for continental Europe, so a single conversion pass keeps headlines and tables aligned.
Secondary-school and college physics and environmental-science courses assign problems that give consumption on one scale and ask for another, often mixing brochure MPG with lab-style L/100km in the same worksheet. If you later need mass-only conversion, density conversion, or general multi-category unit conversion, treat those as separate search intents and landings rather than overloading this fuel economy converter page.
What you can do with it
Cross-border car listings
Restate US or UK brochure MPG as L/100km or km/L so international shoppers compare the same vehicle on the scale they know.
Homework and review tables
Map student or journalist fuel figures among MPG and metric units without hand-written conversion factors.
FAQ
Why is US MPG different from imperial MPG?
The US liquid gallon is 3.785411784 L while the imperial gallon is 4.54609 L. The same car therefore reports a higher MPG number in imperial units than in US units.
What happens if amount is zero or negative?
Fuel economy must be a positive finite number; zero and negative values are rejected.
How does L/100km relate to km/L?
Lower L/100km means better economy, while higher km/L means better economy.
What does it cost?
The browser tool is free and runs locally.
Why is a lower L/100km number better?
Because L/100km measures consumption, the fuel used per distance, while MPG and km/L measure economy, the distance per fuel. So a car improves when its MPG or km/L rises and when its L/100km falls.
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/fuel-economy \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"amount":30,"from":"mpg_us","to":"l_100km"}'const res = await fetch("https://api.kit.forhosting.com/conv/fuel-economy", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"amount": 30,
"from": "mpg_us",
"to": "l_100km"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/fuel-economy",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"amount": 30,
"from": "mpg_us",
"to": "l_100km"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/fuel-economy", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"amount":30,"from":"mpg_us","to":"l_100km"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"amount":30,"from":"mpg_us","to":"l_100km"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/fuel-economy", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"amount": 30,
"from": "mpg_us",
"to": "l_100km"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.fuel_economy",
"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
This capability accepts one finite positive amount plus from and to unit labels among mpg_us, mpg_imp, km_l, and l_100km, bridges every conversion through kilometers per liter so economy and consumption scales stay consistent, and returns the target value together with the same figure expressed in all four units.
What you send and what you get back from the API and browser form
Send three fields: amount, a finite positive number for the fuel-economy magnitude; from, a string naming the input unit; and to, a string naming the output unit. When a unit string is unknown the error message includes Unrecognized unit and lists the four supported families so clients can fix the label rather than guessing. When amount is not strictly positive the error explains that fuel economy cannot be zero or negative. Classic checks include thirty US MPG becoming about seven point eight four liters per 100 kilometers, twelve L/100km becoming about eight point three three kilometers per liter, and imperial MPG reading higher than US MPG for the same vehicle because the imperial gallon is larger. Both unit fields accept short keys and everyday words in any common casing, including mpg_us or mpg or US miles per gallon, mpg_imp or uk_mpg or imperial miles per gallon, km_l or kpl or kilometers per liter, and l_100km or lp100km or liters per 100 km. Missing fields, non-numeric amount strings, NaN, Infinity, zero, negative amounts, and unrecognized unit labels fail with invalid_input and are not charged. On success the response echoes the cleaned amount, normalized from and to keys, the primary result in the target unit, the same figure as mpg_us, mpg_imp, km_per_l, and l_per_100km with twelve significant digits of stable precision, the bridge factors used when applicable, the formula string, and method km_l_bridge. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where dedicated fuel economy conversion shows up in real work
Data pipelines that ingest mixed OEM or rental payloads with mpg, mpg_uk, and l_100km tags can call this capability once per reading instead of reimplementing the factors in every service. Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.
Integration use cases
Fleet telematics normalization
Convert mixed mpg_us, mpg_imp, and L/100km feeds into one warehouse unit before cost-per-kilometer reports.
Technical questions
Which fuel economy units does this converter support?
US miles per gallon (mpg_us), imperial/UK miles per gallon (mpg_imp), kilometers per liter (km_l), and liters per 100 kilometers (l_100km). Common aliases such as mpg, uk_mpg, kpl, and lp100km are accepted; the response normalizes to short keys.