Unit Converter

Fuel Economy Converter

Named gallons. Clear consumption.

Convert fuel economy

Named gallons. Clear consumption.

Fuel-economy entry method

Fuel-economy value

Positive finite decimal, scientific value, fraction or mixed number. Zero has no finite reciprocal comparison.

From fuel-economy convention

To fuel-economy convention

Planned tripEstimate fuel for a planned trip

The projection applies a constant consumption rate. Driving conditions, idling and route changes are not inferred.

Fuel-only costApply a stated fuel price

Only the stated price is applied. Extra charges, changing prices, other vehicle costs and exchange rates are not added.

Available-fuel rangeEstimate range from available fuel

A constant-rate range estimate is not a guaranteed driving distance.

Equal-distance comparisonCompare with another fuel-economy figure

Positive fuel savings mean the current rate uses less; negative savings mean it uses more. An mpg increase is not the same percentage as a consumption reduction.

View fuel results

Precision and report

Display significant figures

Show exact target ratioShow calculation stepsShow every-metric comparison table

Decimals support twenty significant digits, eighty characters and written exponents from negative thirty through thirty. Fractions support one hundred digits per component and two hundred forty characters per field. Display precision does not improve a vehicle estimate or measurement.

Worked examples

Fuel rate in liters per 100 kilometers

q_t\approx7.84048611111\,\mathrm{L}/(100\,\mathrm{km})

Consumption direction: lower values mean less fuel per distance. Exact numerical arithmetic precedes display rounding.

Fuel-economy conversion record

Entered metric

q_s=30.0000000000\,\mathrm{mpg}_{\mathrm{US}}

Normalized consumption

c\approx0.0784048611111\,\mathrm{L/km}

Consumption per hundred kilometers

c_{100}\approx7.84048611111\,\mathrm{L}/(100\,\mathrm{km})

Distance per liter

e\approx12.7543112229\,\mathrm{km/L}

This changes metric direction, so it uses a reciprocal rather than a fixed linear multiplier. US liquid gallons and Imperial gallons are different volumes.

Economy and consumption in every supported metric

All twelve rows describe the same finite positive rate. Economy and consumption directions are labeled separately, and every row remains in complete text and CSV when this table is hidden.

The same rate in twelve explicit economy and consumption conventions
Convention and direction	Converted rate
Miles per US liquid gallonEconomy: higher means less fuel per distance	$30.0000000000\,\mathrm{mpg}_{\mathrm{US}}$
Miles per Imperial gallonEconomy: higher means less fuel per distance	$\approx\,36.0284977651\,\mathrm{mpg}_{\mathrm{Imp}}$
Kilometers per literEconomy: higher means less fuel per distance	$\approx\,12.7543112229\,\mathrm{km/L}$
Liters per 100 kilometersConsumption: lower means less fuel per distance	$\approx\,7.84048611111\,\mathrm{L}/(100\,\mathrm{km})$
Kilometers per US liquid gallonEconomy: higher means less fuel per distance	$48.2803200000\,\mathrm{km}/\mathrm{gal}_{\mathrm{US}}$
Kilometers per Imperial gallonEconomy: higher means less fuel per distance	$\approx\,57.9822467074\,\mathrm{km}/\mathrm{gal}_{\mathrm{Imp}}$
Miles per literEconomy: higher means less fuel per distance	$\approx\,7.92516157074\,\mathrm{mi/L}$
Liters per 100 milesConsumption: lower means less fuel per distance	$12.6180392800\,\mathrm{L}/(100\,\mathrm{mi})$
Liters per kilometerConsumption: lower means less fuel per distance	$\approx\,0.0784048611111\,\mathrm{L/km}$
US liquid gallons per 100 milesConsumption: lower means less fuel per distance	$\approx\,3.33333333333\,\mathrm{gal}_{\mathrm{US}}/(100\,\mathrm{mi})$
Imperial gallons per 100 milesConsumption: lower means less fuel per distance	$\approx\,2.77558061543\,\mathrm{gal}_{\mathrm{Imp}}/(100\,\mathrm{mi})$
Milliliters per kilometerConsumption: lower means less fuel per distance	$\approx\,78.4048611111\,\mathrm{mL/km}$

Step-by-step fuel-economy calculation

1. Normalize the declared metric direction
Distance per fuel must be inverted after unit normalization; fuel per distance is normalized directly. Zero and negative inputs are rejected rather than silently replaced.
$c\approx0.0784048611111\,\mathrm{L/km}$
2. Express the same rate in the destination convention
Apply the fuel-per-distance convention to normalized consumption. Lower values in this direction mean less fuel per distance.
$q_t\approx7.84048611111\,\mathrm{L}/(100\,\mathrm{km})$

What Can You Create?

Translate fuel rates and document a trip estimate

Compare named economy and consumption metrics

Translate the same positive rate into twelve conventions, including separate US and Imperial mpg. Economy rows describe distance per fuel volume; consumption rows describe fuel per distance, with the favorable direction labeled clearly.

Use matching measured totals or plan a distance

Form a rate from measured total distance and total fuel, then optionally apply it to a planned trip. The source measurement interval and projected distance remain separate, so a forecast is not mistaken for a new observation.

Inspect fuel-only cost, available-fuel range and comparisons

State a fuel price with its liter or gallon convention, choose the fuel amount available for a range model, or compare two rates at equal distance. Every optional result carries its own declared assumptions.

Fuel-economy formulas and step-by-step examples

Normalize consumption as $c=F/D$ . Its reciprocal is economy, $e=D/F=1/c$ , when both measured totals are positive. Keep the distance and liquid-volume definitions explicit before changing direction.

c=\frac{F}{D},\qquad e=\frac{D}{F}=\frac1c

Convert the original thirty-US-mpg example

First use the exact US liquid gallon and international-mile definitions. Then invert the normalized distance-per-fuel figure and express consumption over a hundred kilometers. The final decimal below is rounded for explanation; the calculation keeps the exact ratio.

c_{100}=\frac{100(3.785411784)}{30(1.609344)}=\frac{112903}{14400}\approx7.840486111\quad\mathrm{L}/(100\,\mathrm{km})

Form a rate from measured totals and project a trip

Measured totals of $40\,\mathrm L$ over $500\,\mathrm{km}$ give the rate below. Applying that same rate to a separately planned $250\,\mathrm{km}$ trip gives a numerical fuel projection; it does not account for changed driving conditions.

c=\frac{40\,\mathrm L}{500\,\mathrm{km}}=0.08\,\mathrm{L/km},\qquad F_{\mathrm{trip}}=c(250\,\mathrm{km})=20\,\mathrm L

Compare fuel use over the same distance

For a reference of $24$ US mpg and a current figure of $30$ US mpg, normalize both into consumption. The current rate uses $20\%$ less fuel per equal distance, while the mpg figure itself has increased by $25\%$ . The reciprocal relationship explains why those percentages differ.

S=\frac{c_{\mathrm{ref}}-c}{c_{\mathrm{ref}}}\,100\%=\left(1-\frac{24}{30}\right)100\%=20\%

Apply a volume-specific price or available-fuel amount

Convert the stated price to a price per liter before applying it to projected fuel. For range, divide the entered available fuel by the same consumption rate. Currency units, fuel availability and the modeled rate are inputs supplied by the user.

C=F_{\mathrm{trip}}p_{\mathrm{per\ L}},\qquad R=\frac{F_{\mathrm{available}}}{c}

Why Users Love This Tool

Keep reciprocal direction and gallon conventions explicit

Definitions stay visible

All four original identifiers and the thirty-US-mpg default remain available.
International statute miles, US liquid gallons and Imperial gallons retain their exact definitions.
Zero and negative source rates produce clear validation messages instead of being silently changed.

Planning retains the unrounded numerical model

Measured rates use total fuel divided by total distance before any display rounding.
Equal-distance comparisons calculate fuel reduction rather than assuming that an mpg percentage is a fuel-saving percentage.
Complete copying, CSV and accessible printed mathematics preserve active totals, projections, prices and comparison context.

Perfect For

Useful for mileage notes, liquid-fuel comparisons and dimensional learning

Drivers checking a liquid-fuel figure

Identify which gallon the source uses before comparing numbers. This page converts physical liquid-volume rates; energy-equivalent MPGe ratings need their own energy context and are not treated as actual gallons of a vehicle fuel.

Trip and operating-note preparation

Translate an entered rate into projected fuel at a stated distance, then apply a declared fuel price if helpful. Keep conditions and measurement assumptions in the record instead of treating a constant-rate estimate as observed vehicle performance.

Students reviewing inverse relationships

Follow the difference between distance per fuel and fuel per distance. Check why a larger mpg number can correspond to a smaller consumption number and why the two directions have different percentage changes.

How It Works

How it works in three quick steps.

Declare the metric or matching measured totals

Choose a finite positive fuel-economy figure and its exact convention, or enter positive total distance and fuel consumed over the same interval. Select US liquid gallons or Imperial gallons explicitly when either is involved.

Inspect consumption and enable relevant planning options

Select the destination metric and display significant figures. Optionally enter a planned distance, fuel price with its volume convention, available fuel or a second fuel-economy figure for an equal-distance comparison. Review the normalized consumption and assumptions.

Save the rate and its planning context

Copy the complete record or LaTeX working, download every metric and optional result as CSV, share validated active settings or print the selected visible report to PDF. Keep the gallon convention, measured interval and any price or range assumptions with the result.

Download & Print

Download and print the rate with its full planning context

Copy the full record or LaTeX steps

Copy every metric and active optional result as labeled text, or copy the generated working with display-math delimiters. A versioned share link preserves validated active inputs, selected conventions and report preferences.

Download complete UTF-8 CSV

The quoted file includes all twelve rate conventions, exact numerical certificates, measured totals, trip projections, price context, available-fuel range and comparison assumptions. Hidden table rows and working remain in the complete saved record.

Print or save the selected report to PDF

Choose the table, exact ratio and working sections, then use the browser print dialog. Check a portrait preview before saving. Controls and the supporting article are omitted, while active model assumptions remain attached to the numerical report. Very long ratios stay available in complete text and CSV.

FAQ

Frequently Asked Questions

Why are US mpg and Imperial mpg different?

The mile is the same international statute mile in both choices, but the gallons are different. A US liquid gallon is exactly

3.785411784\,\mathrm L

, while an Imperial gallon is exactly

4.54609\,\mathrm L

. For the same physical consumption, the larger Imperial gallon therefore corresponds to a larger miles-per-gallon number. The converter keeps the gallon labels explicit in every menu and record. It never infers a gallon from a country name, a bare mpg abbreviation or the size of an entered number.

How do I convert US mpg into liters per hundred kilometers?

Normalize the distance and fuel definitions, then take the reciprocal because mpg measures distance per fuel and liters per hundred kilometers measures fuel per distance. With the exact international-mile and US-liquid-gallon factors, the relationship is

c_{100}=100(3.785411784)/(1.609344m_{\mathrm{US}})

. Here the mpg input is the numerical value, and the result is the numerical count of liters per hundred kilometers. The converter keeps the factor as an exact rational quantity rather than using a shortened decimal shortcut throughout the calculation.

Why does the converter reject zero or negative fuel-economy figures?

The comparison table represents one finite positive rate in both economy and consumption directions. Zero in either rate direction does not have a finite reciprocal in the other direction, and a negative value is not a normal finite fuel-use rate for this model. The tool explains that boundary and clears stale output instead of substituting a tiny positive number. Planned distance, entered available fuel and price can separately be zero: those valid optional inputs produce zero projected trip fuel, zero range or zero cost without changing the underlying positive rate.

How should I calculate fuel economy from measured trips?

Use the total distance and the fuel actually consumed over the same measurement interval. Choose the distance and fuel-volume conventions independently. A tank capacity, an unmatched purchase or a refill covering a different interval is not automatically the measured fuel used. For several legs, add their distances and their fuel amounts before entering the totals. An arithmetic mean of trip mpg figures generally does not equal total distance divided by total fuel, particularly when the legs use different amounts of fuel.

Is an mpg improvement the same percentage as a reduction in fuel used?

No. Economy and consumption are reciprocals, so their percentage changes differ. Moving from

24

30

US mpg increases the mpg figure by

25\%

, while fuel use over an equal distance falls by

20\%

. The comparison section normalizes both figures into consumption before calculating the reduction. Positive savings mean the current rate uses less fuel than the reference; negative savings mean it uses more. The same declared fuel price is applied to both scenarios when cost arithmetic is enabled.

How are planned fuel and fuel-only cost estimated?

The tool multiplies normalized consumption by the planned distance, following

F=cD

. If price is enabled, it converts the entered price per liter, US liquid gallon or Imperial gallon into a price per liter before multiplying by the modeled fuel. Currency units are the units you choose for that input; no exchange rate is inferred. The estimate does not add changing prices, charges absent from your stated price, maintenance, tolls or other vehicle costs. Actual driving conditions can also change consumption relative to the assumed constant rate.

Does the available-fuel calculation give a guaranteed driving range?

The modeled range follows

R=F_a/c

, using the available fuel you enter and the same positive consumption rate. The result is shown in kilometers and international miles. No reserve, usable-tank allowance, route condition, weather effect or driving behavior is inferred. Entered available fuel can be zero, which gives zero modeled range. A nominal tank capacity should not automatically be treated as fuel available for a particular trip, and the numerical calculation is an estimate under its assumptions rather than a guaranteed distance.

Are the digits exact, and what do shared or saved records retain?

The defined unit factors and entered numerical model use exact rational arithmetic. Display significant figures affect presentation only and do not improve a vehicle rating, distance reading, fuel measurement or price assumption. Complete text and CSV retain every metric, exact numerical certificates, active measured totals, optional projections, comparison signs and hidden working. Share links restore validated active settings while omitting dormant buffers. PDF follows the selected visible report sections, with extremely long exact ratios kept in complete text and CSV so they do not overflow a printed page.

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About This Tool

About this Fuel Economy Converter

The Toolarithm Fuel Economy Converter treats an economy figure and a consumption figure as two directions of the same positive rate. Distance per fuel volume describes how far a vehicle travels using a stated amount of liquid fuel. Fuel per distance describes the volume used to cover a stated distance. These directions are reciprocal, so the relationship between mpg and liters per hundred kilometers is not a fixed linear multiplier. Making that distinction explicit helps keep unit conversion separate from an assumption about improved vehicle performance.

The page preserves the original thirty-US-mpg example and all four original unit identifiers. Additional named choices include kilometers per US or Imperial gallon, miles per liter, liters per mile-based interval and gallon-based consumption measures. International statute miles and both liquid gallon conventions retain exact definitions. A bare mpg label is not used to infer which gallon was intended, and the converter does not substitute a different number when a source input cannot define a finite positive reciprocal rate.

A measured-entry method forms the rate from total fuel consumed and total distance over the same interval. This also provides a sensible way to use aggregated trip information: enter the combined fuel and distance totals, rather than an unweighted mean of separate mpg figures. The optional planning sections then apply that rate to a separately stated distance, fuel price, available-fuel amount or comparison figure. Each section keeps its purpose and assumptions visible so that a projected trip is not confused with a measurement.

Fuel price is entered in the user's own currency units per selected volume, and the model normalizes it before calculating fuel-only costs. Available-fuel range uses the amount the user chooses to model, without inferring a reserve or a usable-tank allowance. Equal-distance comparisons subtract the current consumption from reference consumption, preserving negative outcomes as increased use rather than clamping them into savings. These are numerical projections under stated assumptions; changing conditions, driving behavior and other vehicle costs require their own information.

Exact rational arithmetic preserves the input model through unit normalization, reciprocal conversion, trip planning and percentage comparisons. Display significant figures remain a presentation choice. Complete text and CSV keep every rate and active assumption, while share links contain canonical validated settings and printed reports follow selected visibility preferences. Server-rendered defaults and accessible MathML keep the initial calculation and supporting examples available before interactive code loads. The tool is a liquid-volume rate converter and does not turn an energy-equivalent MPGe label into a measured volume of vehicle fuel.

Editorial Transparency

Who maintains this page

Ownership and review

Written and maintained by the Toolarithm editorial team. No review date is shown without a maintained editorial record. No independent professional review is claimed.

Methodology

Conversion factors are normalized to canonical units and checked in both directions. Exact definitions and offset formulas are preferred over rounded lookup values.

Read the editorial methodology

Dates and sources

Review dates change only after a substantive method or content check.

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