Normalized distance
350 mi / 563.3 km
Vehicle & Automotive
MPG Calculator
Use this MPG calculator to calculate fuel economy from a real trip, compare US MPG with Imperial MPG, convert to km/L or L/100 km, and estimate fuel cost.
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Calculator
Calculate instantly
US MPG = miles / US gallons; L/100 km = litres / km x 100
The engine normalizes distance to miles and kilometres, normalizes fuel to litres, US gallons, and Imperial gallons, then calculates the common fuel economy measures.
- Distance and fuel are converted into miles, kilometres, litres, US gallons, and Imperial gallons.
- US and Imperial MPG use different gallon sizes.
- The trip cost uses the price entered for your selected fuel unit.
Inputs
Fuel economy and cost inputs
Enter distance, fuel used, fuel units, fuel price, and optional annual distance or tank fuel for planning estimates.
Breakdown
Clear result breakdown
Review the values that explain the primary result.
Normalized fuel
12 US gal / 9.99 Imp gal / 45.42 L
Trip fuel cost
$42.00
Cost per mile
$0.12
Cost per km
$0.0746
Estimated annual fuel cost
$1,440.00
Estimated range
408.3 mi
Visual comparison
Fuel economy comparison
The chart separates common fuel economy units. US and Imperial gallons are not treated as equal.
The chart separates common fuel economy units. US and Imperial gallons are not treated as equal.
US MPG29.17 MPG
Imperial MPG35.03 MPG
km/L12.4 km/L
Practical guidance
Insights for this scenario
US and Imperial gallons differ
The calculator converts both gallon types through litres so MPG comparisons remain honest.
Real-world results vary
Traffic, speed, weather, tyre pressure, cargo, route, maintenance, and driving style can move the real number.
Cost estimates use your entered price
Trip and annual cost are planning estimates based on the selected fuel unit and price.
Step-by-step solution
Follow the calculation path from known values to final result.
- 1
Normalize units
Distance and fuel are converted into miles, kilometres, litres, US gallons, and Imperial gallons.
350 miles and 45.42 L
- 2
Calculate fuel economy
MPG = miles / gallons
US and Imperial MPG use different gallon sizes.
29.17 US MPG
- 3
Estimate cost
trip cost = fuel used x price
The trip cost uses the price entered for your selected fuel unit.
$42.00
Formula explorer
US MPG = miles / US gallons; L/100 km = litres / km x 100
The engine normalizes distance to miles and kilometres, normalizes fuel to litres, US gallons, and Imperial gallons, then calculates the common fuel economy measures.
- d(miles or kilometres)
- Distance: Distance travelled during the measured trip.
- F(litres, US gallons, or Imperial gallons)
- Fuel used: Fuel consumed during the measured trip.
- P(currency per unit)
- Fuel price: Price per selected fuel unit used for cost estimates.
Assumptions and references
Units
- mi
- gal
Assumptions
- Distance and fuel represent the same measured trip.
- Fuel price is entered per selected fuel unit.
- Annual fuel cost assumes similar efficiency across the annual distance.
Limitations
- Treating US and Imperial gallons as equal.
- Entering fuel price per litre while the fuel unit is gallons.
- Using one short trip as an official vehicle fuel rating.
- Results depend on the accuracy of the values entered.
- Rounding may make displayed values slightly different from exact intermediate calculations.
Worked examples
Real-worldRoad trip fuel economy
Known values
- Distance: 350 miles
- Fuel used: 12 US gallons
Calculation
- 1. Divide 350 by 12 for US MPG.
- 2. Convert US gallons to litres and Imperial gallons.
- 3. Calculate km/L and L/100 km from the normalized values.
Result and meaning
The trip is about 29.17 US MPG, 35.03 Imperial MPG, or 12.40 km/L.
Learning guide
Understand the calculation
Concepts
- Fuel economy can be expressed as distance per fuel or fuel per distance.
- Lower L/100 km means better efficiency, while higher MPG or km/L means better efficiency.
- US gallons and Imperial gallons are different sizes.
Tips
- Use the same fill-up method for more accurate tracking.
- Compare similar driving conditions.
- Use annual distance only as a planning assumption.
Common mistakes
- Mixing US and Imperial MPG.
- Entering fuel price per litre while fuel is set to gallons.
- Treating one short trip as official fuel economy.
Educational notes
- The calculator normalizes distance and fuel through miles, kilometres, litres, US gallons, and Imperial gallons so fuel economy units stay consistent.
- Traffic, driving style, load, maintenance, tire pressure, and route conditions affect real results.
- Yes. Convert MPG, km/L, and L/100km before comparing.
- Use it as an estimate and compare it with the formula, assumptions, and examples shown on the page.
- Real-world inputs can include local rules, changing rates, measurement tolerances, and conditions outside the core formula.
Glossary
- Distance
- Distance travelled during the measured trip.
- Fuel used
- Fuel consumed during the measured trip.
- Fuel price
- Price per selected fuel unit used for cost estimates.
Trust panel
Calculator quality and review
- Reviewed by
- AZCalculate automotive calculator review
- Review date
- 2026-06-25
- References
- 2
- Trust score
- 93/100
- Formula verified
- Yes
- Risk level
- medium
- Category
- Vehicle & Automotive
- Calculator version
- 2.1
- Formula version
- 2.1
Sign in to save this calculation and access it later.
Trust note
Planning estimate
Use this result as a practical estimate. Real-world conditions, local rules, measurement tolerance, and changing inputs can affect the final outcome.
Medium risk contextDifficulty: easyConfidence estimate: 93/100Reviewed 2026-06-25Reviewed by: AZCalculate automotive calculator reviewCalculator v2.1 / Formula v2.12 sources listed
Formula and Explanation
US MPG = miles / US gallons; Imperial MPG = miles / Imperial gallons; L/100 km = litres / kilometres x 100
The calculator normalizes distance and fuel through miles, kilometres, litres, US gallons, and Imperial gallons so fuel economy units stay consistent.
Variable descriptions
- d(miles or kilometres)
- Distance: Distance travelled during the measured trip.
- F(litres, US gallons, or Imperial gallons)
- Fuel used: Fuel consumed during the measured trip.
- P(currency per unit)
- Fuel price: Price per selected fuel unit used for cost estimates.
Formula Notes
- US and Imperial gallons are not equal.
- L/100 km becomes better as the number decreases.
- Cost estimates use the fuel price and unit selected by the user.
Common uses
- Track fuel economy
- Compare vehicles
- Estimate trip fuel
- Track real fuel economy
- Compare US and Imperial MPG
Assumptions
What this calculation assumes
- Distance and fuel represent the same measured trip.
- Fuel price is entered per selected fuel unit.
- Annual fuel cost assumes similar efficiency across the annual distance.
Avoid mistakes
Quick checks before you rely on the result
- Treating US and Imperial gallons as equal.
- Entering fuel price per litre while the fuel unit is gallons.
- Using one short trip as an official vehicle fuel rating.
Step-by-Step Explanation
Follow the reasoning, not only the final number.
- 1
Set up the calculation
Enter distance driven and choose miles or kilometres.
Starting with clearly defined values and units prevents the most common calculation errors.
- 2
Work through step 2
Enter fuel used and choose litres, US gallons, or Imperial gallons.
This step transforms the known values into the form required by the formula.
- 3
Work through step 3
Normalize the values into common units.
This step transforms the known values into the form required by the formula.
- 4
Work through step 4
Calculate MPG, km/L, and L/100 km.
This step transforms the known values into the form required by the formula.
- 5
Interpret the result
Use fuel price and annual distance for cost estimates.
Compare the result with your real-world goal, such as track fuel economy.
Worked example
Road trip MPG example
Known values
- Distance: 350 miles
- Fuel used: 12 US gallons
Calculation
- 1. Divide 350 by 12 to get US MPG.
- 2. Convert 12 US gallons to litres and Imperial gallons.
- 3. Calculate km/L and L/100 km from the normalized values.
Result and meaning
The trip is about 29.17 US MPG, 35.03 Imperial MPG, 12.40 km/L, and 8.06 L/100 km.
Calculator guide
About this MPG Calculator
Calculate miles per gallon, gallons per 100 miles, and trip fuel. This page includes an interactive calculator, concise formula notes, worked examples, FAQs, related calculators, and practical guidance you can revisit whenever needed.
References
Sources used for this calculator
Last checked: 2026-06-25 | Next review: 2026-12-25
Last checked: 2026-06-25 | Next review: 2026-12-25
Found something that does not look right?
We work hard to keep every calculator accurate and useful. If you notice a calculation error, missing option, or unclear explanation, please let us know so we can review and correct it promptly.
Calculator usage
Usage information loads after the calculator is ready.
FAQ
MPG Calculator FAQs
How does the mpg calculator work?+
It uses MPG = miles / gallons and calculates the result from the values you enter.
Can I copy or print the result?+
Yes. AZCalculate calculator pages include copy, share, and print actions.
What is MPG?+
MPG means miles per gallon. It shows how many miles a vehicle travels for each gallon of fuel used.
Are US MPG and Imperial MPG the same?+
No. A US gallon and an Imperial gallon are different sizes, so the calculator converts both through litres before showing both MPG values.
How do I calculate L/100 km from a trip?+
Divide litres used by kilometres travelled, then multiply by 100. A lower L/100 km means better fuel economy.
Can I enter litres instead of gallons?+
Yes. Enter fuel used in litres, US gallons, or Imperial gallons and choose miles or kilometres for distance.
Why is my real-world MPG different?+
Traffic, speed, weather, tyre pressure, vehicle load, fuel quality, maintenance, and driving style can all change real fuel economy.
Can this estimate trip fuel cost?+
Yes. Enter the fuel price per selected fuel unit to estimate trip cost, cost per mile, cost per kilometre, and annual fuel cost.
Can I estimate driving range?+
Yes. Enter tank or available fuel to estimate range using the calculated fuel economy.
Does this show official vehicle fuel economy?+
No. It calculates fuel economy from your entered trip data and should not be treated as an official vehicle rating.
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