Answer first
What this calculator tells you
Convert between US miles per gallon, imperial miles per gallon, liters per 100 km and kilometers per liter. Compare a car's rating in the unit used where you live with one quoted elsewhere. Formula: Convert through kilometers per liter: 1 US mpg = 0.425144 km/L, 1 imperial mpg = 0.354006 km/L, L/100 km = 100 ÷ (km/L). At the worked-example inputs, the converted value is 7.84. Holding every other input steady, moving value from 24 to 36 moves the result from 6.53 to 9.80.
Transparent method
The formula
Compare a car's rating in the unit used where you live with one quoted elsewhere.
Worked example
Example inputs
How to interpret the result
Fuel economy is quoted in opposite directions: miles per gallon says how far one gallon goes, and liters per 100 kilometers says how much fuel a distance takes. That inversion makes the conversion nonlinear. Thirty US miles per gallon is about 7.84 liters per 100 kilometers, and thirty imperial miles per gallon is about 9.42, because the imperial gallon is larger. The unit of the gallon decides the answer. Reference values: 25 US mpg is about 9.4 liters per 100 kilometers, 40 US mpg is about 5.9 and 50 US mpg is about 4.7. One US mpg is about 0.425 kilometers per liter.
At the worked-example inputs the converted value is 7.84. It falls as from, to and value increase.
Conversion factors are exact defined constants; results are limited only by floating-point precision, not by real-world estimation.
Before you rely on it
What to check
Check which gallon a rating uses. A UK figure in miles per gallon is imperial, and the same number in the US means a smaller gallon and less distance.
The common error
Where people go wrong with fuel economy converter calculator
Averaging the ratings of two cars in miles per gallon to guess a combined figure. The fuel used adds up in liters per distance, so the arithmetic average is wrong.
Sensitivity evidence
How value changes the converted value
Holding every other input at the worked-example value, moving value from 24 to 36 moves the converted value from 6.53 to 9.80: a spread of 3.27, or 42% of the worked-example result.
| Value | Converted value | Same economy in L/100 km |
|---|---|---|
| 24 | 9.80 | 9.80 |
| 27 | 8.71 | 8.71 |
| 30worked example | 7.84 | 7.84 |
| 33 | 7.13 | 7.13 |
| 36 | 6.53 | 6.53 |
Every input, tested
Which input moves the converted value most
Of the 3 inputs, from moves the converted value most (4.51 across the range tested) and value moves it least (1.58).
| Input | Tested from | To | Converted value at each end | Swing |
|---|---|---|---|---|
| From | Miles per gallon (US) | Kilometers per liter | 7.84 to 3.33 | 4.51 (340%) |
| To | Miles per gallon (US) | Kilometers per liter | 30.00 to 12.75 | 17.25 (360%) |
| Value | 27 | 33 | 8.71 to 7.13 | 1.58 (20%) |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Value | 30 | Enter the value used in this calculation. |
| From | Miles per gallon (US) | Unit to convert from. |
| To | Liters per 100 km | Unit to convert to. |
| Converted value | 7.84 | |
| Same economy in L/100 km | 7.84 | |
Inputs, definitions and assumptions
Value
Enter the value used in this calculation. The prefilled worked-example value is 30.
From
Unit to convert from. The prefilled worked-example value is Miles per gallon (US).
To
Unit to convert to. The prefilled worked-example value is Liters per 100 km.
How to use this calculator
- 1Verify the inputs. Gather value, from and to from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the converted value at 7.84. Store your own version of it as Scenario A.
- 3Test one change. Start with from, the input with the biggest effect here: switching from changes the converted value: miles per gallon (US) gives 7.84; miles per gallon (imperial) gives 9.42; liters per 100 km gives 30.00; kilometers per liter gives 3.33.
- 4Check the boundary. Read the interpretation boundary above before acting on the result.
People also ask
Frequently asked questions
How do you calculate fuel economy converter?
Convert through kilometers per liter: 1 US mpg = 0.425144 km/L, 1 imperial mpg = 0.354006 km/L, L/100 km = 100 ÷ (km/L). At the worked-example inputs the converted value is 7.84.
What does the fuel economy converter result mean?
Compare a car's rating in the unit used where you live with one quoted elsewhere. At the worked-example inputs the converted value is 7.84. It falls as from, to and value increase.
How much does value change the converted value?
Holding every other input at the worked-example value, moving value from 24 to 36 moves the converted value from 6.53 to 9.80, a spread of 3.27.
What are the limits of this fuel economy converter calculator?
Conversion factors are exact defined constants; results are limited only by floating-point precision, not by real-world estimation. The tables on this page test value only from 24 to 36; a value outside that range is not tabulated here.
Which input moves the converted value most in the fuel economy converter calculator?
Ranked by how far each moves the converted value across the range tested: from (4.51, 340%), to (17.25, 360%) and value (1.58, 20%).
How much does from matter in the fuel economy converter calculator?
The worked example uses Miles per gallon (US). With the other inputs left at the worked example, switching from changes the converted value: miles per gallon (US) gives 7.84; miles per gallon (imperial) gives 9.42; liters per 100 km gives 30.00; kilometers per liter gives 3.33.
How much does to matter in the fuel economy converter calculator?
The worked example uses Liters per 100 km. Holding every other input at its worked-example value, switching to changes the converted value: miles per gallon (US) gives 30.00; miles per gallon (imperial) gives 36.03; liters per 100 km gives 7.84; kilometers per liter gives 12.75.
Which inputs change the same economy in l/100 km in the fuel economy converter calculator?
At the worked-example inputs it is 7.84. Value takes it from 8.71 to 7.13 and from takes it from 7.84 to 3.33.
Why is a year 365.25 days in the time converter?
Every fourth year adds a day, so the average calendar year is about 365.25 days. For a contract or a birthday, count calendar dates instead of using an average year.
Is a horsepower the same everywhere?
No. A mechanical horsepower is about 745.7 watts and a metric horsepower is about 735.5. A car spec can quote either, so check which before comparing engines.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.