US MPG to European convention
The default conversion, through the reciprocal.
Input
30 MPG (US) → L/100kmOutput
7.84 L/100km — and 12.75 km/L, 36.03 UK MPG alongsideFuel Economy Converter
Convert US MPG, UK MPG, km/L, and L/100km — handling the reciprocal math where lower is better — with all four measures shown at once.
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- Processing clearly labeled
- Instant results
Content last reviewed
30.00 US MPG equals
7.84L/100km
Decimals
Every measure at once
Quick reference
| US MPG | UK MPG | L/100km | km/L |
|---|---|---|---|
| 15 | 18.0 | 15.68 | 6.38 |
| 20 | 24.0 | 11.76 | 8.50 |
| 25 | 30.0 | 9.41 | 10.63 |
| 30 | 36.0 | 7.84 | 12.75 |
| 40 | 48.0 | 5.88 | 17.01 |
| 50 | 60.0 | 4.70 | 21.26 |
| 60 | 72.1 | 3.92 | 25.51 |
Watch the direction. MPG and km/L are "distance per fuel" — higher is better. L/100km is "fuel per distance" — lower is better. That's why L/100km is the reciprocal: L/100km = 100 ÷ (km/L).
US and UK gallons differ: an imperial (UK) gallon is ~20% larger, so 30 UK MPG is noticeably thirstier than 30 US MPG. Always check which gallon a figure uses.
Quick Start
Enter the figure
Type the fuel-economy value — anything above zero.
Pick From and To
US MPG, UK MPG, km/L, or L/100km, with a swap button.
Read all four
The headline pair converts exactly, and every measure shows alongside.
Examples
A frugal European figure in MPG
Lower L/100km is better; the reciprocal turns it into a high MPG.
Input
5 L/100km → MPG (US)Output
47.04 US MPG (20 km/L)About the Fuel Economy Converter
Fuel economy is quoted four different ways, and two of them point in opposite directions: miles per gallon and kilometres per litre measure distance per fuel (higher is better), while litres per 100 km measures fuel per distance (lower is better). Converting between them is not a simple factor — L/100km is the reciprocal of the others — and on top of that, a UK gallon is 20% larger than a US one, so "40 MPG" means two different cars depending on the country. This converter untangles all of it.
Enter a figure, pick its unit — US MPG, UK MPG, km/L, or L/100km — and the exact conversion appears, with all four measures displayed together so a spec sheet from any market reads instantly. The math pivots through km/L with each unit's own transform, using the exact gallon definitions (US 3.785411784 L, imperial 4.54609 L) and mile (1.609344 km). A reference table of common MPG values gives the ladder — 15 to 60 US MPG — in every measure at once.
The practical wins: comparing an American car review against a European brochure, translating your trip computer's L/100km into the MPG your intuition grew up on, and checking a used import's claimed economy in your own market's terms. Precision controls and one-click copy round out the workflow.
How to Use Fuel Economy Converter
Type the fuel economy value — it must be above zero, since these measures are ratios.
Pick the From unit: miles per gallon (US), miles per gallon (UK), litres per 100 km, or kilometres per litre.
Pick the To unit and read the headline result — or take any measure from the every-measure-at-once panel.
Use swap to reverse the pair, the decimals control to set precision, and copy for the result.
Check the reference table for the common-MPG ladder across all four measures.
Key Features
All four common measures
US MPG, UK MPG, km/L, and L/100km — including the two-gallons problem and the reciprocal one.
Correct reciprocal handling
L/100km inverts against the distance-per-fuel measures; the converter does the reciprocal math exactly.
Every measure at once
One figure rendered in all four conventions simultaneously.
Exact gallon definitions
US gallon 3.785411784 L and imperial gallon 4.54609 L — the 20% gap handled explicitly.
Reference ladder
Common MPG values (15–60) shown across every measure for instant context.
When to Use Fuel Economy Converter
Cross-market car shopping
Compare US reviews, UK brochures, and European spec sheets on one scale.
Trip-computer translation
Turn the dashboard's L/100km into the MPG (or km/L) your intuition uses.
Import checks
Verify a used import's claimed economy in your own market's convention.
Trip budgeting
Convert to L/100km — the measure that multiplies cleanly by distance for fuel-cost estimates.
How It Works
Every unit converts through kilometres per litre as the pivot. The MPG units are linear against it — one US MPG is 1.609344 ÷ 3.785411784 ≈ 0.4251 km/L, one UK MPG ≈ 0.3540 km/L, the difference being the gallon — while L/100km is the reciprocal: km/L = 100 ÷ (L/100km) and back again. That reciprocal is why fuel-per-distance and distance-per-fuel cannot share a simple factor, and why zero is excluded: the reciprocal of zero consumption is not a number.
A side effect worth knowing: because of the reciprocal, equal-looking MPG improvements are not equal fuel savings — going from 15 to 20 MPG saves more fuel per distance than going from 40 to 50. Thinking in L/100km makes savings linear, which is why fleet operators prefer it.
Supported Formats and Options
Options
From / To with swap
Any pair of the four measures, reversible in one click.
Decimals and notation
Precision from 0–6 places (default 2) with a scientific-notation toggle.
Copy and reset
Copy the result as a plain number; reset restores the 30 US MPG → L/100km default.
Common Errors and Troubleshooting
Common errors
Mixing US and UK MPG
The gallons differ by 20%, so 40 UK MPG ≈ 33 US MPG for the same car. Always check which market a brochure figure comes from — the converter carries both explicitly.
Entering zero or a negative value
Fuel-economy measures are positive ratios, and the L/100km reciprocal is undefined at zero — the tool asks for a value above zero.
Assuming lower is always worse
Direction flips between conventions: higher MPG is better, but lower L/100km is better. Compare within one convention after converting.
Troubleshooting guide
Reading economy figures like a buyer
- Brochure vs. reality: official figures come from standardized test cycles and typically overstate real-world economy in every market. Convert them for comparison between cars, not as a promise per tank.
- Fuel budgeting: convert to L/100km, multiply by trip distance ÷ 100, then by the fuel price — the fuel-per-distance form is the one that multiplies cleanly.
- Comparing improvements: judge upgrades in L/100km, where savings are linear; MPG gains flatter at the top of the scale.
- Electric and hybrid figures: kWh/100km and MPGe are different quantities — this converter covers the four liquid-fuel conventions.
Limitations and Important Notes
The four conventions covered are the liquid-fuel standards — electric-vehicle measures (kWh/100km, MPGe) are different quantities and out of scope. Values must be positive, since the reciprocal transform is undefined at zero. The converter translates between conventions; it cannot make an official test-cycle figure match real-world driving.
Privacy and Data Processing
Conversions are computed in your browser; nothing entered is transmitted or saved.
Tips and Best Practices
Practical tips
Confirm whether an MPG figure is US or UK before comparing — the gallons differ 20%.
Budget fuel in L/100km, the form that multiplies cleanly by distance and price.
Compare efficiency improvements in L/100km, where savings are linear.
Treat official figures as comparable test results, not per-tank promises.
Use the all-measures panel to annotate a spec sheet in every convention at once.
Best practices
Comparing cars across conventions
Normalize every candidate to one measure — L/100km if spreadsheets are involved, since it multiplies directly into running costs: annual distance ÷ 100 × L/100km × fuel price is the yearly fuel bill, and suddenly the comparison is in money rather than folklore.
Mind the reciprocal intuition trap when weighing upgrades: replacing the thirstiest car in a household saves more fuel than upgrading an already-efficient one by the same MPG step. Convert both cars to L/100km and subtract — the honest saving falls out immediately.
Technical Details
Conversion pivots through km/L with per-unit transforms: US MPG × (1.609344/3.785411784), UK MPG × (1.609344/4.54609), and L/100km as the reciprocal (100 ÷ value in both directions). Inputs are validated positive. Precision defaults to 2 decimals (0–6 plus scientific notation), and copy payloads are plain numbers. Fully client-side.
Comparison
The same car in four conventions
| US MPG | UK MPG | km/L | L/100km |
|---|---|---|---|
| 20 | 24.0 | 8.5 | 11.8 |
| 30 | 36.0 | 12.8 | 7.8 |
| 40 | 48.0 | 17.0 | 5.9 |
| 50 | 60.1 | 21.3 | 4.7 |
Note the direction flip — MPG and km/L rise with efficiency while L/100km falls — and the constant 20% UK/US gallon gap.
Who Is This For?
Car shoppers reading reviews and brochures across markets, drivers translating their dashboard's convention, importers checking claimed figures, and anyone budgeting fuel for a trip. The reciprocal and two-gallon traps make this one of the conversions genuinely worth a dedicated tool.
Frequently Asked Questions
How do I convert MPG to L/100km?
Through the reciprocal: convert MPG to km/L (US MPG × 0.4251), then L/100km = 100 ÷ km/L. 30 US MPG works out to 7.84 L/100km — the converter does both steps exactly.
Why do US and UK MPG differ for the same car?
The gallons differ: imperial 4.546 L versus US 3.785 L, about 20%. The same car scores ~20% higher in UK MPG — 40 UK MPG and 33 US MPG describe identical fuel use.
Which measure is best for comparing cars?
L/100km, because fuel savings are linear in it: each 1 L/100km cut saves the same litres per distance regardless of where you start. MPG's reciprocal scale exaggerates gains between already-efficient cars.
Why can't I enter zero?
L/100km is the reciprocal of the distance-per-fuel measures, and the reciprocal of zero is undefined — zero fuel use would be infinite MPG. The tool requires a positive value.
Does this cover electric vehicles?
No — EV efficiency uses kWh/100km or MPGe, which measure energy rather than fuel volume. This converter covers the four liquid-fuel conventions.