MPG

Automotive

Fuel Economy Calculator

Calculate real-world fuel economy from distance and fuel used, convert between L/100 km, km/L, US MPG, and Imperial MPG, compare driving scenarios, visualize efficiency, and export a professional PDF record.

Distance traveled (km)Fuel used (liters)Fuel price per liter

Consumption (L/100 km)-

Efficiency (km/L)-

US miles per gallon-

Imperial miles per gallon-

Fuel cost for this trip-

Efficiency sensitivity

Trip cost under alternative fuel economy

Trip fuel costSame distance and fuel price

Consumption	Fuel required	US MPG	Imperial MPG	Trip cost	Cost per 100 km

How to use Fuel Economy Calculator

Enter the distance covered by one consistent measurement interval.
Enter the fuel needed to refill to the same tank level.
Enter the price per litre used for the cost calculation.
Compare consumption scenarios on the live cost-versus-economy curve.

Calculator guide

Understanding Fuel Economy Calculator

A fill-to-fill fuel record connects one measured distance with the fuel needed to refill the tank. The same observation can be expressed as consumption, distance per litre, US MPG, Imperial MPG, and trip fuel cost without mixing gallon definitions.

One observation All units come from the same distance and refill.

Inverse scales Lower L/100 km means higher km/L and MPG.

Two gallons US and Imperial MPG are not interchangeable.

Live cost curve Price and consumption move trip cost together.

Calculation method

How the calculation works

Fuel economy in L/100 km = liters used / kilometers driven x 100. Divide litres by kilometres and scale to 100 km, invert that rate for kilometres per litre, apply the stated gallon conversion constants, and multiply the measured litres by price.

Detailed calculation process

Convert one distance-and-refill record into comparable economy measures

The default record covers 620 km, uses 46 L, and prices fuel at $1.75 per litre.

General formula: c = 100V/de = d/V = 100/cMPG_US = 235.214583/cMPG_Imp = 282.481/cC_trip = Vp Consumption c measures litres needed per 100 km, while efficiency e measures kilometres obtained per litre. The two MPG constants convert the same metric consumption rate using different gallon sizes. Trip cost values the measured refill volume at the entered price.

What each symbol means

d Measured distance traveled (km).

V Fuel used over that distance (L).

c Fuel consumption (L/100 km).

e Distance efficiency (km/L).

MPG_US, MPG_Imp Miles per US gallon and miles per Imperial gallon (mi/gal).

p, C_trip Fuel price ($/L) and fuel cost for the measured trip ($).

Worked substitution with the default inputs

1. Calculate metric consumption c = 100(46 L)/(620 km)c = 7.419355 L/100 km Scaling the observed litres-per-kilometre ratio by 100 gives the standard consumption unit.

2. Invert the observation e = 620 km/46 Le = 13.478261 km/L This expresses the same record as distance obtained from one litre.

3. Convert to both MPG conventions MPG_US = 235.214583/7.419355 = 31.7028 mpgMPG_Imp = 282.481/7.419355 = 38.0735 mpg Imperial MPG is numerically larger because an Imperial gallon is larger than a US gallon.

4. Value the measured fuel C_trip = (46 L)($1.75/L)C_trip = $80.50 Litres cancel against the per-litre price, leaving currency.

5. Reconcile the reciprocal measures (7.419355 L/100 km)(13.478261 km/L) = 100$80.50/620 km × 100 = $12.98 per 100 km The reciprocal product checks the two economy measures; the cost check translates the same trip into a normalized distance cost.

The defaults equal 7.419 L/100 km, 13.478 km/L, 31.70 US MPG, 38.07 Imperial MPG, and $80.50 for the measured 620 km trip.

Efficiency relationship

Read consumption, MPG, and trip cost on one curve

The relationship view plots realistic consumption scenarios, with the current observation highlighted and the corresponding trip cost recalculated.

Current point The entered distance and litres anchor the comparison.

Lower consumption Fuel volume and trip cost fall for the same distance.

MPG conversion The inverse efficiency scale changes in the opposite direction.

Price response Every scenario updates when price changes.

Worked situations

Practical examples

A 620 km interval using 46 L produces 7.419 L/100 km.
The same observation equals 13.478 km/L rather than a different efficiency result.
At $1.75/L, the recorded fuel costs $80.50.

Better inputs

Useful tips

Use several full-tank records to reduce pump shutoff and short-trip noise.
Keep distance and fuel units consistent before comparing vehicles.
Separate seasonal, towing, city, and highway records when operating conditions differ.

Before relying on the result

Limitations and common mistakes

One refill can be distorted by pump cutoff, tank angle, odometer error, idling, or incomplete refilling.
Displayed MPG uses fixed conversion constants and does not infer the user's regional gallon convention.
The trip-cost result excludes maintenance, depreciation, tolls, parking, and other vehicle costs.

Reference

Key terms

Consumption: Fuel volume required for a fixed distance; lower L/100 km is more efficient.
Efficiency: Distance obtained per unit of fuel; higher km/L or MPG is more efficient.
US gallon: A volume of about 3.785 litres.
Imperial gallon: A volume of about 4.546 litres.

Important note

Calculated from the entered vehicle and operating values. Actual prices, financing terms, efficiency, maintenance, insurance, taxes, and resale outcomes can differ.

Frequently asked questions

Why does lower L/100 km mean better economy?

It means fewer litres are needed to cover the same 100 km.

Why are US and Imperial MPG different?

They use different gallon volumes, so the same vehicle record produces different numbers.

Can I use miles and gallons directly?

This page's inputs are kilometres and litres; convert source measurements first.

Does one fill represent long-term economy?

Not necessarily. A multi-fill average better represents varied conditions.