First step: fill the tank completely, choose the fuel type and enter the current odometer reading. The first entry does not need a fuel amount or price.

Initial full tank

Overall average

No data yet. Enter the odometer reading at the first full tank to start your fuel log.

Fill-ups and consumption intervals

Date and odometerDistanceAddedConsumptionCost

Data and backups

Entries are stored only in this browser. Use a JSON backup to restore them and CSV to view the log in a spreadsheet.

How to use the fuel consumption tracker

Four steps from the first full tank to a reliable average.

Set a starting point

Fill the tank completely, select the fuel type and save the current odometer reading. No fuel amount is needed for the first entry.

Log the next full fill-up

When you next fill the tank completely, enter the new odometer reading, the amount added and, optionally, what you paid.

Review the results

See consumption for every interval, the weighted overall average, distance covered and fuel-cost summary.

Back up your log

Download JSON to restore or move the editable log, or CSV to open the data in a spreadsheet.

What matters when measuring real fuel consumption?

For reliable comparisons, use the same full-to-full method and do not skip complete fill-ups.

Fill to the same level

Only close an interval when the tank has been filled completely again. A partial top-up does not finish an accurate interval.

Log consistently

Record the odometer and amount after every full fill-up. More consecutive intervals make the overall average more useful.

Compare intervals

A sudden change may reflect traffic, weather, speed, load, tyre pressure or the mechanical condition of the car.

Fuel economy formula, overall average and example

Fuel consumption (l/100 km) = litres added ÷ distance since the previous full tank × 100. If the odometer moves from 15,000 to 15,200 km and the tank takes 10 litres, consumption is 5.0 l/100 km.

The overall result is a weighted average. Total fuel used is divided by total distance, so a longer interval has more influence than a short one.

Odometer readings may be entered in kilometres or miles. Results can be shown as l/100 km, km/l, US mpg or UK mpg.

Cost totals appear once a price has been entered for every fill-up after the starting point.

How to reduce fuel use and interpret changes

Check tyre pressures when the tyres are cold and follow the vehicle manufacturer’s figures. Under-inflation increases rolling resistance.

Drive smoothly, read the road ahead and avoid needless hard acceleration and braking. Higher speeds also increase aerodynamic drag.

Remove unused roof racks and unnecessary weight. Loads, trailers and open windows at speed can all affect consumption.

An unexpected rise may point to tyres, brakes, engine issues or another fault. Look at several fill-ups before calling it a trend.

Town driving, congestion, cold starts, temperature, wind, hills, air conditioning and heating can all change one interval.

More useful tools for driving and travel

Plan a journey with the fuel cost calculator, or keep parking, accommodation and other holiday spending in the travel tracker.

Fuel cost calculator

Calculate journey cost, consumption and distance for a chosen budget.

Travel expense tracker

Log fuel, accommodation, food, parking and other holiday spending.

EV charging calculator

Estimate charging time, energy required and charging cost.

Fuel consumption tracker: common questions

Full-to-full fill-ups, MPG units, costs, privacy and backups.

How is real fuel consumption calculated?
Fill the tank completely each time. Save only the odometer at the first fill, then record the next odometer reading and the amount needed to refill the tank.
Can I enter a partial fill-up?
Only if that amount brings the tank back to full. A partial top-up does not complete a full-to-full interval and would distort the result.
Does the first entry need a fuel amount?
No. The first full tank is the starting point, so only its odometer reading is required.
How is the overall average calculated?
Fuel from all completed intervals is divided by their total distance. This weighted average gives longer intervals the appropriate influence.
Can I use miles and MPG?
Yes. Use kilometres or miles for the odometer and display consumption as l/100 km, km/l, US mpg or UK mpg.
What is the difference between US and UK mpg?
The gallons differ: a US gallon is 3.785 litres and an imperial gallon is 4.546 litres.
Where is my data stored?
Only in this browser on this device. Clearing site data may remove it, so download a JSON backup for an important log.
What are JSON and CSV for?
JSON restores the editable log or moves it to another device. CSV is a spreadsheet report and cannot be imported.