How do I calculate my vehicle's real mileage (km/L)?

Use the full-to-full method: fill the tank completely and note the odometer. Next time you fill completely, divide the kilometres travelled by the litres it took to refill. That works because a full tank is the only repeatable reference point. fuelbook automates this over your whole log, folding partial fill-ups into the correct tank segment.

Is my fuel log private? Does fuelbook work offline?

Yes. fuelbook has no account, no cloud, and no analytics. Its Content-Security-Policy sets connect-src to none, so the browser itself blocks any network send. Your log lives only in this browser's localStorage; CSV export is your backup.

Why does my km/L change from tank to tank?

Pump auto-cutoffs stop at slightly different levels, so what counts as 'full' varies a little each time. That makes any single tank's figure wobble by a few percent. Trust the lifetime line, computed across many tanks, over any one tank's number.

What is the true cost per km of my vehicle?

Fuel alone understates it. fuelbook computes fuel-only cost per km and an all-in figure that adds service, insurance, tyres and other expenses over the same first-full-to-last-full window, so both numbers cover exactly the same kilometres.

Fuel Mileage Calculator & Fill-Up Log — True km/L and Cost per km, Tank to Tank

Log every fill-up; fuelbook turns it into honest tank-to-tank mileage and the true all-in cost of every kilometre — using the full-to-full method, with its limits stated right here on screen.

Private by construction: this page's security policy blocks all network sends, so your log cannot leave this browser.

Add my first fill-up

Dashboard

Tank-to-tank trend

One point per full-to-full tank. The dashed line is your trailing 3-tank average.

Fill-up log

Manual entry only — fuelbook has no receipt OCR, no OBD/Bluetooth, and no GPS. You type it, it stays yours.

Fill-up entries, newest first
Date	Odometer	Litres	Amount	Price/L	Type	Note	Actions

No fill-ups yet. Add your first full fill above — km/L appears after your second full fill.

Other expenses

Service, insurance, tyres and the rest — they join the all-in cost per km over the same first-full-to-last-full window as your fuel.

Expense entries, newest first
Date	Category	Amount	Note	Status	Actions

No expenses yet.

The method, in plain words

Full-to-full: a mileage segment runs between two consecutive FULL fills. Segment km/L = kilometres between them ÷ every litre poured after the previous FULL through this FULL (partial top-ups in between are folded in and the segment is labelled includes partial). It works because a full tank is the only repeatable reference point.

Its honest limits

km/L exists only between two FULL fills. A log of partials shows spend totals, but fuelbook refuses to guess mileage — it says "need two full fills to compute".
Entries before your first FULL or after your last FULL are excluded from km/L, with the reason shown on screen. They join after your next full fill.
"Full" varies with the pump's auto-cutoff, so single-tank figures wobble a few percent. Trust the lifetime line over any one tank.
All-in cost per km covers only the first-FULL-to-last-FULL window; expenses dated outside it are flagged and join after the next full fill.
The trend note is a prompt to check tyre pressure, service due, or fuel quality — never a mechanical diagnosis.

Export & backup

Your log lives only in this browser's storage — clearing site data erases it. CSV export is your backup and your handoff.

Settings

Vehicle name Vehicle type Currency symbol Units Digit grouping Claimed km/L (optional)

Units change labels and arithmetic only — stored entries are never converted. The claimed figure is a personal reference line, as entered by you; fuelbook ships no claimed-mileage database.