Mileage and Fuel Economy Calculator

Fill-to-fill fuel economy

One refill. One clear mileage result.

Enter the two odometer readings and the fuel used to see real-world MPG, km/L, and L/100 km from the same trip.

Your fuel economy

Equivalent units, calculated from the same refill.

Distance per gallon35.26MPG

Metric equivalent: 6.67 L/100 km
Distance per litre: 14.99 km/L

Distance driven: 335 Miles
Fuel added: 9.5 US gal

Calculation details

Subtract the previous complete-fill reading from the current reading.distance traveled = current odometer − previous odometer
Normalize distance to kilometres and fuel to litres.1 international mile = 1.609344 km; 1 U.S. gallon = 3.785411784 L
Divide distance by fuel or use the reciprocal consumption form.economy = distance / fuel; L/100 km = fuel × 100 / km

For a meaningful fill-to-fill estimate, use two comparable complete fill-ups and the fuel added at the second fill. Partial fills, pump shutoff differences, odometer error, idling, and mixed fuels affect the result.
This calculator does not retrieve a route, fuel price, EPA vehicle rating, maintenance condition, or emissions estimate. Entered price is a scenario value only.

1
Fill upRecord the odometer.
2
Drive normallyUse the vehicle as usual.
3
Fill up againEnter the new reading and fuel.

Observed refill economy

Calculate fuel economy from one complete refill interval

An odometer-and-refill calculation measures what happened between two comparable fill-ups. The distance travelled and fuel needed to return the tank to the same reference level can be expressed as MPG, kilometres per litre, or litres per 100 kilometres.

Side-by-side guide · Observed refill economy

Choose an economy convention before comparing vehicles

Travelled distance: Current odometer − previous odometer
MPG or km/L: Distance ÷ fuel added
L/100 km: 100 × litres ÷ kilometres

Miles per U.S. gallon
Divide miles by U.S. gallons. A higher MPG means more distance from each gallon. State U.S. gallon explicitly because an imperial gallon has a different volume.
Kilometres per litre
Divide kilometres by litres. Like MPG, a higher number indicates more distance per unit of fuel, but the numeric scale is different and should not be compared directly with MPG.
Litres per 100 kilometres
Divide litres by kilometres and multiply by 100. This is consumption per fixed distance, so lower is more efficient. It is not obtained by simply relabelling a km/L result.

Calculate fuel economy from one complete refill interval: An odometer-and-refill calculation measures what happened between two comparable fill-ups. The distance travelled and fuel needed to return the tank to the same reference level can be expressed as MPG, kilometres per litre, or litres per 100 kilometres.

A same-refill interval ties the numerator to the denominator

Record an odometer reading immediately after filling the tank to a consistent stopping point. At the next fill, record the new odometer and the fuel dispensed to reach that same reference. Subtract the readings to obtain the interval distance, then divide by the added fuel for distance-per-volume economy. The fuel purchased at the second stop is used to replace what was consumed during the completed interval; it is not a forecast for the next trip.

A single partial fill cannot establish comparable tank levels. Dashboard estimates can be useful operationally, but they are not the same observation as odometer distance divided by pump quantity. For a planned journey whose route distance and expected economy are already known, use the fuel cost calculator instead of treating a forecast as a measured refill result.

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Divide miles by U.S. gallons. A higher MPG means more distance from each gallon. State U.S. gallon explicitly because an imperial gallon has a different volume.

Kilometres per litre

Divide kilometres by litres. Like MPG, a higher number indicates more distance per unit of fuel, but the numeric scale is different and should not be compared directly with MPG.

Litres per 100 kilometres

Divide litres by kilometres and multiply by 100. This is consumption per fixed distance, so lower is more efficient. It is not obtained by simply relabelling a km/L result.

Run the calculation as a short recording routine

Verify odometer direction
The current reading must exceed the previous reading for an ordinary forward interval. Account explicitly for an odometer replacement or rollover rather than accepting a negative distance.
Enter the actual refill quantity
Use the pump receipt in the selected gallon or litre convention. Tank capacity is not fuel consumed, and a price total cannot replace volume unless the exact unit price is also known.
Keep raw values before rounding
Carry the exact distance difference and entered fuel through the division. Round only the displayed economy so repeated intervals can later be combined from total distance and total fuel.

One tank is an observation, not a permanent vehicle rating

Cold starts, temperature, traffic, speed, grade, payload, tyre pressure, remote starting, and accessory use can change an interval. Compare several complete fills before drawing a trend.
Pump shutoff and parking slope introduce fill-level variation. The error is proportionally larger on short intervals, so a longer ordinary interval generally provides a more stable refill estimate.
EPA label values follow standardized test procedures and are useful reference points, but actual on-road results vary. A refill calculation does not prove a vehicle is defective or certify emissions performance.
For tyre setup rather than fuel accounting, consult the vehicle placard and the tyre and rim manufacturers' current pressure limits. Use the tire dimensions calculator only to compare nominal size relationships; a fuel-economy observation cannot recommend an inflation pressure or certify fit.

Turn measured economy into a transparent cost estimate

Multiplying fuel used by the entered price per gallon or litre gives the fuel cost for the measured interval. Divide that cost by interval distance to obtain a historical cost per mile or kilometre. It excludes maintenance, depreciation, insurance, parking, and tolls. Verify route-specific tolls with the relevant facility operators rather than describing fuel cost as total ownership cost.

Keep the dates, odometer readings, volume unit, fuel quantity, price basis, and unusual driving notes. When evaluating a destination, do not substitute straight-line city spacing for distance travelled; the city distance calculator explicitly reports geographic separation, not the road mileage that belongs in a fuel record.

Important limitations

Mileage and Fuel Economy Calculator is limited to the finite inputs, modes, and outputs stated for the Trip fuel economy from odometer readings and refill volume method. Check previous odometer reading, current odometer reading, odometer distance unit, fuel added, and fuel unit, validation messages, the equation, and the stated display precision before relying on distance traveled, miles per U.S. gallon, kilometres per litre, and litres per 100 kilometres.

This formula passed its registered engineering tests and is published under an explicit site-owner policy authorization. No independent expert, QA, editorial, legal, or third-party review is claimed. Verify consequential results with a qualified professional.

Observed refill economy

Calculate fuel economy from one complete refill interval

Side-by-side guide · Observed refill economy

Choose an economy convention before comparing vehicles

Travelled distance: Current odometer − previous odometer
MPG or km/L: Distance ÷ fuel added
L/100 km: 100 × litres ÷ kilometres

Miles per U.S. gallon
Divide miles by U.S. gallons. A higher MPG means more distance from each gallon. State U.S. gallon explicitly because an imperial gallon has a different volume.
Kilometres per litre
Divide kilometres by litres. Like MPG, a higher number indicates more distance per unit of fuel, but the numeric scale is different and should not be compared directly with MPG.
Litres per 100 kilometres
Divide litres by kilometres and multiply by 100. This is consumption per fixed distance, so lower is more efficient. It is not obtained by simply relabelling a km/L result.

A same-refill interval ties the numerator to the denominator

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Divide miles by U.S. gallons. A higher MPG means more distance from each gallon. State U.S. gallon explicitly because an imperial gallon has a different volume.

Kilometres per litre

Divide kilometres by litres. Like MPG, a higher number indicates more distance per unit of fuel, but the numeric scale is different and should not be compared directly with MPG.

Litres per 100 kilometres

Divide litres by kilometres and multiply by 100. This is consumption per fixed distance, so lower is more efficient. It is not obtained by simply relabelling a km/L result.

Run the calculation as a short recording routine

Verify odometer direction
The current reading must exceed the previous reading for an ordinary forward interval. Account explicitly for an odometer replacement or rollover rather than accepting a negative distance.
Enter the actual refill quantity
Use the pump receipt in the selected gallon or litre convention. Tank capacity is not fuel consumed, and a price total cannot replace volume unless the exact unit price is also known.
Keep raw values before rounding
Carry the exact distance difference and entered fuel through the division. Round only the displayed economy so repeated intervals can later be combined from total distance and total fuel.

One tank is an observation, not a permanent vehicle rating

Cold starts, temperature, traffic, speed, grade, payload, tyre pressure, remote starting, and accessory use can change an interval. Compare several complete fills before drawing a trend.
Pump shutoff and parking slope introduce fill-level variation. The error is proportionally larger on short intervals, so a longer ordinary interval generally provides a more stable refill estimate.
EPA label values follow standardized test procedures and are useful reference points, but actual on-road results vary. A refill calculation does not prove a vehicle is defective or certify emissions performance.
For tyre setup rather than fuel accounting, consult the vehicle placard and the tyre and rim manufacturers' current pressure limits. Use the tire dimensions calculator only to compare nominal size relationships; a fuel-economy observation cannot recommend an inflation pressure or certify fit.

Mileage and Fuel Economy Calculator

One refill. One clear mileage result.

Enter this fill-up

Your fuel economy

Calculate fuel economy from one complete refill interval

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Kilometres per litre

Litres per 100 kilometres

A same-refill interval ties the numerator to the denominator

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Kilometres per litre

Litres per 100 kilometres

Run the calculation as a short recording routine

One tank is an observation, not a permanent vehicle rating

Turn measured economy into a transparent cost estimate

Important limitations

One refill. One clear mileage result.

Enter this fill-up

Your fuel economy

Calculate fuel economy from one complete refill interval

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Kilometres per litre

Litres per 100 kilometres

A same-refill interval ties the numerator to the denominator

Choose an economy convention before comparing vehicles

Miles per U.S. gallon

Kilometres per litre

Litres per 100 kilometres

Run the calculation as a short recording routine

One tank is an observation, not a permanent vehicle rating

Turn measured economy into a transparent cost estimate