Fuel Economy Converter (MPG, L/100km, km/L, mi/L)
Convert fuel economy between MPG (US & UK), L/100km, km/L, and mi/L. Enter a value in any field and compare the rest instantly.
Enter one number or paste from a spec sheet, then click Calculate. Decimal precision is adjustable below and controls how many digits appear in every field.
Converter inputs
Latest input
—
Enter a value and calculate to populate conversions.
L/100km
—
MPG (US)
—
MPG (UK)
—
km/L
—
mi/L
—
How to use this converter
Start with any known fuel economy value, pick the field that matches its units, and hit Calculate. Every field will update automatically so you can compare across regions and reporting standards.
Toggle the reference table below to see standard tiers (4–12 L/100km) along with the equivalent MPG and km/L numbers. Adjust the decimal places to match your source data or to keep the interface tidy.
Enter positive numbers only. The converter relies on exact relationships between miles, kilometers, and liters, so keep the units consistent when you paste from another document.
Methodology
Internally the calculator normalizes every value to L/100km using the precise relationships between miles, kilometers, liters, US gallons, and Imperial gallons. From there, it derives all other units via reciprocal relationships so the conversions remain consistent with industry standards.
- MPG (US/UK) and mi/L report distance per volume while L/100km is a consumption measure (fuel per distance).
- The tool uses reciprocal calculations to switch between consumption and economy units.
- Decimal precision controls the visible digits and does not affect the underlying values.
Typical fuel economy ranges
- 10–12 L/100km (~19–24 US MPG) – older or large SUVs in city driving.
- 7–8 L/100km (~29–34 US MPG) – average modern compact car.
- 5–6 L/100km (~39–47 US MPG) – efficient diesel or hybrid vehicles.
- <4 L/100km (>59 US MPG) – very efficient hybrids or plug-in vehicles.
Fuel economy vs. fuel consumption
Some regions report economy (higher numbers are better), while others report consumption (lower numbers are better). Always convert values to the same unit type before comparing across regions.
- Economy (higher is better): MPG (US/UK), km/L, mi/L.
- Consumption (lower is better): L/100km, gal/100mi.
Operational notes
Use realistic values and keep timeframes consistent when comparing vehicles. The converter is deterministic across browsers thanks to explicit rounding.
Inputs used by this calculator
- Miles per gallon (US)
- Miles per gallon (UK / Imperial)
- Liters per 100 kilometers
- Kilometers per liter
- Miles per liter
Consistency checks
Every input is validated for positivity. Decimal precision must be between 1 and 4. Invalid entries hide the results until corrected.
About the author
Ugo Candido builds calculators and educational resources with transparent, practical models.
Contact: info@calcdomain.com
Editorial policy
CalcDomain content is created for education, reviewed for clarity, and shows assumptions directly so readers can replicate the math.
Full original guide (expanded)
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<li><span class="text-gray-800">Fuel Economy Converter (MPG, L/100km, km/L, mi/L)</span></li>
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<h1 class="text-2xl font-bold mb-2">
Fuel Economy Converter (MPG, L/100km, km/L, mi/L)
</h1>
<p class="text-gray-700">
Convert fuel economy between MPG (US & UK), L/100km, km/L,
and mi/L. Enter a value in any unit and see all others update
instantly.
</p>
</header>
<section aria-labelledby="converter-heading" class="mb-8">
<h2 id="converter-heading" class="text-xl font-semibold mb-4">
Fuel economy conversions
</h2>
<div class="grid md:grid-cols-2 gap-4 mb-4">
<div>
<label
for="fe-mpg-us"
class="block text-sm font-medium text-gray-700 mb-1"
>
Miles per gallon (US)
<span class="ml-1 text-xs text-gray-500">(mpg US)</span>
</label>
<input
id="fe-mpg-us"
type="number"
step="0.0001"
inputmode="decimal"
class="w-full border border-gray-300 rounded-md px-3 py-2 focus:ring-2 focus:ring-blue-500 focus:border-transparent"
placeholder="e.g. 30"
/>
</div>
<div>
<label
for="fe-mpg-uk"
class="block text-sm font-medium text-gray-700 mb-1"
>
Miles per gallon (UK / Imperial)
<span class="ml-1 text-xs text-gray-500">(mpg UK)</span>
</label>
<input
id="fe-mpg-uk"
type="number"
step="0.0001"
inputmode="decimal"
class="w-full border border-gray-300 rounded-md px-3 py-2 focus:ring-2 focus:ring-blue-500 focus:border-transparent"
placeholder="e.g. 40"
/>
</div>
<div>
<label
for="fe-l-per-100km"
class="block text-sm font-medium text-gray-700 mb-1"
>
Liters per 100 kilometers
<span class="ml-1 text-xs text-gray-500">(L/100km)</span>
</label>
<input
id="fe-l-per-100km"
type="number"
step="0.0001"
inputmode="decimal"
class="w-full border border-gray-300 rounded-md px-3 py-2 focus:ring-2 focus:ring-blue-500 focus:border-transparent"
placeholder="e.g. 7.5"
/>
</div>
<div>
<label
for="fe-km-per-l"
class="block text-sm font-medium text-gray-700 mb-1"
>
Kilometers per liter
<span class="ml-1 text-xs text-gray-500">(km/L)</span>
</label>
<input
id="fe-km-per-l"
type="number"
step="0.0001"
inputmode="decimal"
class="w-full border border-gray-300 rounded-md px-3 py-2 focus:ring-2 focus:ring-blue-500 focus:border-transparent"
placeholder="e.g. 15"
/>
</div>
<div>
<label
for="fe-mi-per-l"
class="block text-sm font-medium text-gray-700 mb-1"
>
Miles per liter
<span class="ml-1 text-xs text-gray-500">(mi/L)</span>
</label>
<input
id="fe-mi-per-l"
type="number"
step="0.0001"
inputmode="decimal"
class="w-full border border-gray-300 rounded-md px-3 py-2 focus:ring-2 focus:ring-blue-500 focus:border-transparent"
placeholder="e.g. 25"
/>
</div>
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<option value="2" selected>2</option>
<option value="3">3</option>
<option value="4">4</option>
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Clear all
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</section>
<section aria-labelledby="quick-comparison-heading" class="mb-8">
<h2
id="quick-comparison-heading"
class="text-xl font-semibold mb-3"
>
Quick comparison table
</h2>
<p class="text-sm text-gray-700 mb-2">
See how common fuel economy values compare across units.
</p>
<div class="overflow-x-auto border border-gray-200 rounded-md">
<table class="min-w-full text-sm">
<thead class="bg-gray-100">
<tr>
<th
class="px-3 py-2 text-left font-semibold text-gray-700"
>
L/100km
</th>
<th
class="px-3 py-2 text-left font-semibold text-gray-700"
>
MPG (US)
</th>
<th
class="px-3 py-2 text-left font-semibold text-gray-700"
>
MPG (UK)
</th>
<th
class="px-3 py-2 text-left font-semibold text-gray-700"
>
km/L
</th>
</tr>
</thead>
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id="fe-sample-table-body"
class="divide-y divide-gray-100"
>
<!-- Filled by JS -->
</tbody>
</table>
</div>
</section>
<section class="prose">
<h2>How this fuel economy converter works</h2>
<p>
This tool converts between the most common fuel economy and fuel
consumption units used worldwide:
</p>
<ul>
<li>
<strong>MPG (US)</strong> – miles per US gallon (3.785 L)
</li>
<li>
<strong>MPG (UK)</strong> – miles per Imperial gallon
(4.546 L)
</li>
<li><strong>L/100km</strong> – liters per 100 kilometers</li>
<li><strong>km/L</strong> – kilometers per liter</li>
<li><strong>mi/L</strong> – miles per liter</li>
</ul>
<p>
Enter a value in <em>any</em> field and the calculator will
instantly update all the others using precise conversion
factors. You can also adjust the number of decimal places to
match your needs.
</p>
<h2>Conversion formulas</h2>
<p>
Internally, the converter uses exact relationships between
distance and volume units.
</p>
<div class="formula-box text-sm">
<p class="font-semibold mb-1">Base constants</p>
<ul class="list-disc pl-5">
<li>1 mile = 1.609344 km</li>
<li>1 US gallon = 3.785411784 L</li>
<li>1 UK (Imperial) gallon = 4.54609 L</li>
</ul>
</div>
<h3>From L/100km to MPG and km/L</h3>
<p>
L/100km is a <em>consumption</em> unit (fuel per distance). MPG
and km/L are <em>economy</em> units (distance per fuel). That’s
why the formulas use a reciprocal.
</p>
<div class="formula-box text-sm">
<p>Let \( C \) be fuel consumption in L/100km.</p>
<p class="mt-2">
US MPG: \[ \text{MPG}_{US} = \frac{235.214583}{C} \]
</p>
<p>UK MPG: \[ \text{MPG}_{UK} = \frac{282.480936}{C} \]</p>
<p>km/L: \[ \text{km/L} = \frac{100}{C} \]</p>
<p>mi/L: \[ \text{mi/L} = \frac{62.137119}{C} \]</p>
</div>
<h3>From MPG to L/100km</h3>
<div class="formula-box text-sm">
<p>Let \( E_{US} \) be US MPG and \( E_{UK} \) be UK MPG.</p>
<p class="mt-2">
From US MPG: \[ C = \frac{235.214583}{E_{US}} \]
</p>
<p>From UK MPG: \[ C = \frac{282.480936}{E_{UK}} \]</p>
</div>
<h3>From km/L and mi/L</h3>
<div class="formula-box text-sm">
<p>Let \( K \) be km/L and \( M \) be mi/L.</p>
<p class="mt-2">L/100km from km/L: \[ C = \frac{100}{K} \]</p>
<p>L/100km from mi/L: \[ C = \frac{62.137119}{M} \]</p>
<p>
US MPG from km/L: \[ \text{MPG}_{US} = K \cdot
\frac{100}{3.785411784} \]
</p>
<p>
UK MPG from km/L: \[ \text{MPG}_{UK} = K \cdot
\frac{100}{4.54609} \]
</p>
</div>
<h2>Typical fuel economy values</h2>
<p>
Very roughly, you can think of these ranges for passenger cars:
</p>
<ul>
<li>
<strong>10–12 L/100km</strong> (≈ 19–24 US MPG) – older or
large SUVs, city driving
</li>
<li>
<strong>7–8 L/100km</strong> (≈ 29–34 US MPG) – average modern
compact car
</li>
<li>
<strong>5–6 L/100km</strong> (≈ 39–47 US MPG) – efficient
diesel or hybrid
</li>
<li>
<strong>< 4 L/100km</strong> (≈ > 59 US MPG) – very
efficient hybrids or plug‑in hybrids
</li>
</ul>
<h2>Fuel economy vs. fuel consumption</h2>
<p>
It’s easy to get confused because some countries report how far
you can drive on a unit of fuel, while others report how much
fuel you need to drive a fixed distance:
</p>
<ul>
<li>
<strong>Economy (higher is better)</strong>: MPG, km/L, mi/L
</li>
<li>
<strong>Consumption (lower is better)</strong>: L/100km,
gal/100mi
</li>
</ul>
<p>
When comparing cars across regions (for example, US MPG vs
European L/100km), always convert to the same type of measure
first.
</p>
</section>
</div>
<section class="mt-10" id="author">
<h2 class="text-xl font-semibold mb-4">About the author</h2>
<div class="bg-gray-50 border border-gray-200 rounded-lg p-4">
<p class="text-sm text-gray-700">
<a href="https://www.linkedin.com/in/ugocandido92821/" class="text-blue-600 hover:underline" target="_blank" rel="noopener">Ugo Candido</a>
builds financial tools and educational resources to help
readers make better money decisions. He focuses on practical,
transparent models that reflect how lenders calculate
payments and total cost of ownership.
</p>
<p class="text-sm text-gray-700 mt-3">
Contact: <a href="mailto:info@calcdomain.com" class="text-blue-600 hover:underline">info@calcdomain.com</a>
</p>
</div>
</section>
<section class="mt-10" id="editorial-policy">
<h2 class="text-xl font-semibold mb-4">Editorial policy</h2>
<div class="bg-gray-50 border border-gray-200 rounded-lg p-4">
<p class="text-sm text-gray-700">
CalcDomain content is created for educational purposes and is
reviewed for clarity, accuracy, and transparency. We do not
accept paid placements that influence calculator outputs.
Inputs and assumptions are shown directly in the interface so
you can verify how results are produced.
</p>
</div>
</section>
<section class="mt-10" id="methodology">
<h2 class="text-xl font-semibold mb-4">Methodology</h2>
<div class="bg-gray-50 border border-gray-200 rounded-lg p-4">
<p class="text-sm text-gray-700">
Results use standard formulas and the values you provide.
Figures are estimates and may differ from lender quotes.
For decisions that require professional guidance, consult a
licensed advisor.
</p>
</div>
</section>
<section class="mt-10" id="sources">
<h2 class="text-xl font-semibold mb-4">Sources</h2>
<div class="bg-gray-50 border border-gray-200 rounded-lg p-4">
<ul class="list-disc list-inside text-sm text-gray-700 space-y-1">
<li>
<a href="https://www.nist.gov/pml/owm/metric-si/si-units" class="text-blue-600 hover:underline" target="_blank" rel="noopener">
NIST: The International System of Units (SI)
</a>
</li>
<li>
<a href="https://openstax.org/details/books/college-algebra" class="text-blue-600 hover:underline" target="_blank" rel="noopener">
OpenStax: College Algebra
</a>
</li>
</ul>
</div>
</section>
<section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Operational notes</h2><p class="text-sm text-gray-700">Fill in realistic values and keep units and timeframes consistent.</p><p class="text-sm text-gray-700 mt-2">Key entities: Conversions, Fuel, Economy, Miles per gallon (US) (mpg US), Miles per gallon (UK / Imperial) (mpg UK), Liters per 100 kilometers (L/100km), Kilometers per liter (km/L), Miles per liter (mi/L).</p></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Inputs used by this calculator</h2><ul class="text-sm text-gray-700 list-disc pl-5"><li>Miles per gallon (US) (mpg US)</li><li>Miles per gallon (UK / Imperial) (mpg UK)</li><li>Liters per 100 kilometers (L/100km)</li><li>Kilometers per liter (km/L)</li><li>Miles per liter (mi/L)</li></ul></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Consistency checks</h2><p class="text-sm text-gray-700">Checks: non-negative values, plausible ranges, coherent outputs.</p></section><!-- %%EEAT_STRIP%% -->
<!-- %%QUALITY_BLOCKS%% -->
<!-- %%FAQ_JSONLD%% -->
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<script src="/assets/js/mobile-menu.js"></script>
<script src="/search.js"></script>
<script>
(function () {
const MPG_US_PER_MPG_UK = 0.83267418463; // 1 UK MPG ≈ 1.20095 US MPG -> inverse
const KM_PER_MILE = 1.609344;
const L_PER_US_GAL = 3.785411784;
const L_PER_UK_GAL = 4.54609;
const inputs = {
mpgUs: document.getElementById("fe-mpg-us"),
mpgUk: document.getElementById("fe-mpg-uk"),
lPer100: document.getElementById("fe-l-per-100km"),
kmPerL: document.getElementById("fe-km-per-l"),
miPerL: document.getElementById("fe-mi-per-l"),
};
const precisionSelect = document.getElementById("fe-precision");
const resetBtn = document.getElementById("fe-reset");
const sampleBody = document.getElementById("fe-sample-table-body");
let updating = false;
function getPrecision() {
const p = parseInt(precisionSelect.value, 10);
return isNaN(p) ? 2 : p;
}
function round(value) {
if (!isFinite(value)) return "";
const p = getPrecision();
return Number(value.toFixed(p));
}
function fromLPer100(C) {
const kmPerL = 100 / C;
const miPerL = (100 * KM_PER_MILE) / (100 * C); // simplifies to KM_PER_MILE / C
const mpgUs = (100 * KM_PER_MILE) / (C * L_PER_US_GAL);
const mpgUk = (100 * KM_PER_MILE) / (C * L_PER_UK_GAL);
return { kmPerL, miPerL, mpgUs, mpgUk };
}
function updateFromLPer100(value) {
const C = parseFloat(value);
if (!isFinite(C) || C <= 0) {
clearAllExcept("lPer100");
return;
}
const res = fromLPer100(C);
inputs.kmPerL.value = round(res.kmPerL);
inputs.miPerL.value = round(res.miPerL);
inputs.mpgUs.value = round(res.mpgUs);
inputs.mpgUk.value = round(res.mpgUk);
}
function updateFromMpgUs(value) {
const mpgUs = parseFloat(value);
if (!isFinite(mpgUs) || mpgUs <= 0) {
clearAllExcept("mpgUs");
return;
}
const C = 235.214583 / mpgUs;
inputs.lPer100.value = round(C);
updateFromLPer100(C);
}
function updateFromMpgUk(value) {
const mpgUk = parseFloat(value);
if (!isFinite(mpgUk) || mpgUk <= 0) {
clearAllExcept("mpgUk");
return;
}
const C = 282.480936 / mpgUk;
inputs.lPer100.value = round(C);
updateFromLPer100(C);
}
function updateFromKmPerL(value) {
const kmPerL = parseFloat(value);
if (!isFinite(kmPerL) || kmPerL <= 0) {
clearAllExcept("kmPerL");
return;
}
const C = 100 / kmPerL;
inputs.lPer100.value = round(C);
updateFromLPer100(C);
}
function updateFromMiPerL(value) {
const miPerL = parseFloat(value);
if (!isFinite(miPerL) || miPerL <= 0) {
clearAllExcept("miPerL");
return;
}
const C = (KM_PER_MILE * 100) / (miPerL * 100); // simplifies to KM_PER_MILE / miPerL
const Cexact = KM_PER_MILE / miPerL;
inputs.lPer100.value = round(Cexact);
updateFromLPer100(Cexact);
}
function clearAllExcept(key) {
Object.keys(inputs).forEach((k) => {
if (k !== key) inputs[k].value = "";
});
}
function attachListeners() {
inputs.lPer100.addEventListener("input", () => {
if (updating) return;
updating = true;
updateFromLPer100(inputs.lPer100.value);
updating = false;
});
inputs.mpgUs.addEventListener("input", () => {
if (updating) return;
updating = true;
updateFromMpgUs(inputs.mpgUs.value);
updating = false;
});
inputs.mpgUk.addEventListener("input", () => {
if (updating) return;
updating = true;
updateFromMpgUk(inputs.mpgUk.value);
updating = false;
});
inputs.kmPerL.addEventListener("input", () => {
if (updating) return;
updating = true;
updateFromKmPerL(inputs.kmPerL.value);
updating = false;
});
inputs.miPerL.addEventListener("input", () => {
if (updating) return;
updating = true;
updateFromMiPerL(inputs.miPerL.value);
updating = false;
});
precisionSelect.addEventListener("change", () => {
// Re-run last non-empty field to re-round values
const order = ["lPer100", "mpgUs", "mpgUk", "kmPerL", "miPerL"];
for (const key of order) {
const el = inputs[key];
if (el.value !== "") {
updating = true;
switch (key) {
case "lPer100":
updateFromLPer100(el.value);
break;
case "mpgUs":
updateFromMpgUs(el.value);
break;
case "mpgUk":
updateFromMpgUk(el.value);
break;
case "kmPerL":
updateFromKmPerL(el.value);
break;
case "miPerL":
updateFromMiPerL(el.value);
break;
}
updating = false;
break;
}
}
});
resetBtn.addEventListener("click", () => {
Object.values(inputs).forEach((el) => (el.value = ""));
});
}
function buildSampleTable() {
const sampleL = [4, 5, 6, 7, 8, 10, 12];
const rows = sampleL
.map((C) => {
const res = fromLPer100(C);
const mpgUs = (100 * KM_PER_MILE) / (C * L_PER_US_GAL);
const mpgUk = (100 * KM_PER_MILE) / (C * L_PER_UK_GAL);
return `
<tr>
<td class="px-3 py-1.5">${C.toFixed(1)}</td>
<td class="px-3 py-1.5">${mpgUs.toFixed(1)}</td>
<td class="px-3 py-1.5">${mpgUk.toFixed(1)}</td>
<td class="px-3 py-1.5">${res.kmPerL.toFixed(2)}</td>
</tr>
`;
})
.join("");
sampleBody.innerHTML = rows;
}
attachListeners();
buildSampleTable();
})();
</script>
<script>
window.MathJax = {
tex: {
inlineMath: [
["\\(", "\\)"],
["$", "$"],
],
displayMath: [
["$", "$"],
["\\[", "\\]"],
],
},
svg: { fontCache: "global" },
};
</script>
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var loadMathJax = function () {
if (window.__mathjaxLoading) return;
window.__mathjaxLoading = true;
var script = document.createElement("script");
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script.async = true;
script.src = "https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml.js";
document.head.appendChild(script);
};
var target = document.querySelector(
".formula-box, .mathjax, .math, .formula, [data-mathjax]"
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if (!target) return;
if ("IntersectionObserver" in window) {
var observer = new IntersectionObserver(
function (entries) {
if (entries.some(function (entry) { return entry.isIntersecting; })) {
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loadMathJax();
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{ rootMargin: "200px" }
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observer.observe(target);
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window.addEventListener(
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setTimeout(loadMathJax, 1000);
},
{ once: true }
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