Gallons to Liters

Reading a Per-Litre Pump Price With a Gallon Habit

You pull off a motorway outside Lyon or across the border in Quebec, and the price board shows something like 1.79. For a second it looks like the bargain of the trip. Then the nozzle keeps running past the point where a tank should be full, and the total on the display climbs to three figures.

The board is quoting a litre, and a litre is roughly a quarter of what you are used to buying. Until you put both sides on one scale, a foreign forecourt gives you no feel at all for whether you are paying more or less than at home, and no feel for what a whole tank is about to cost.

Conversion factor: 1 US gallon = 3.785411784 L exactly. Multiply a per-litre price by 3.7854 to get the per-gallon price, and multiply a gallon tank rating by the same number for litres. A pump at 1.79 per litre is 6.78 per US gallon; an 18 gal tank is 68.14 L.

Where the Gallon Habit Trips You Up Abroad

The board is a quarter of the number you expect

Nothing on a European or Canadian forecourt is priced per gallon, so a figure that reads as cheap is really about 3.79 times bigger than it looks.

Your tank is still a gallon figure

Owner's manuals and rental paperwork from home quote capacity in gallons. To know how many litres will go in, and what that costs, the tank has to move to metric first.

Budgeting a driving holiday

Working out fuel for a two-week road trip means turning per-litre prices into something you can weigh against the number you remember from your last fill at home.

Working Out a Fill Before You Squeeze the Handle

Do this once on the first day of the trip and you will carry the feel for the rest of it. The same two boxes handle the tank volume and, with a little care about what the number means, the price.

Enter the tank rating from the handbook

Type the gallon capacity into the left field. A comma or a dot both act as the decimal mark, and spaces are stripped out, so 18.5 and 18,5 arrive at the same place.

Read the litres the pump will count

The right field updates as you type, without a convert button. That figure is what the display will climb to on a dry-to-full fill, so multiplying it by the board price gives the total to expect.

Go the other way for a jerry can or a receipt

Both fields are editable, so a 20 L can typed on the right reads back in gallons on the left. The swap button (↔) reverses the pair permanently when most of your figures arrive in litres.

Copy the litre figure into your expense sheet

The copy button beside each field puts the bare number on the clipboard with no unit and no thousands spacing, which is what a mileage claim or a shared trip budget wants. Ctrl + C in the field does the same.

For price rather than volume the arithmetic is identical but the direction reverses in your head: a price per litre is multiplied by 3.7854 to become a price per gallon, because you are buying 3.7854 of the smaller unit each time.

Pump Price Per Litre Against Price Per US Gallon

The figures below are in whatever currency the forecourt is using — the ratio is the same everywhere. The last two columns show the damage on a 60 L fill and on a 15 US gallon tank, which is 56.78 L.

Board price per litre	Same price per US gallon	Cost of a 60 L fill	Cost of a 15 gal (56.78 L) tank
1.20	4.54	72.00	68.14
1.40	5.30	84.00	79.49
1.60	6.06	96.00	90.85
1.80	6.81	108.00	102.21
2.00	7.57	120.00	113.56
2.20	8.33	132.00	124.92
2.40	9.08	144.00	136.27

Two things still sit outside the arithmetic. One is the exchange rate, which you have to apply separately before any of this is comparable with a price at home. The other is tax: most of the gap between forecourts in different countries is duty and VAT rather than the cost of the fuel itself, so a cheap-looking border town is usually a tax boundary.

Do not fill a rental to its brochure figure. A quoted tank capacity includes reserve the pump cannot always reach, and automatic cut-off usually stops a little short. Budget the converted litres as a ceiling, not as the amount that will actually go in.

What Makes the Forecourt Maths Quicker

A live answer while you stand at the pump

Every keystroke updates the second field, so you can try three tank sizes or three prices in a row without pressing anything between them.

Runs in either direction

Type litres on the right to read gallons on the left, or hit the ↔ button to reverse the pair outright once the whole trip is being counted in metric.

Searchable lists on both sides

all 28 volume units are in the dropdowns, so the same page also handles imperial gallons, quarts or cubic metres if the paperwork changes unit on you.

Clean digits for a claim form

Each field's copy button strips the unit and the spacing, so the value lands in a spreadsheet cell as a number rather than as text.

Questions at a Foreign Filling Station

Why does a European price board look so much cheaper than it is?

Because you are reading a litre price with a gallon-shaped expectation. A litre is 0.264 of a US gallon, so any per-litre figure has to be multiplied by 3.7854 before it can sit beside a number from home. A board showing 1.90 is 7.19 per US gallon. On top of that comes the exchange rate, and fuel duty in much of Europe is several times the American level, so the honest comparison usually ends up worse rather than better.

Does Canada sell fuel by the imperial gallon?

Not since metrication. Canadian pumps switched to litres around 1979 and every forecourt has priced that way for decades, so the number on the board is directly comparable with one in France, not with an American gallon price. The imperial gallon still turns up in conversation and in older Canadian paperwork, and it is a different size again at 4.54609 L, so if a document really does say gallons, check which kind before converting.

How much should I expect a full tank to cost on the road?

Convert your tank first, then multiply. A 15 gallon tank is 56.78 L, so at a board price of 1.80 that is a fill of about 102 in local currency. Realistically you will pay less, because you rarely arrive completely dry and the nozzle cuts off before the very top. As a working rule, budget for about 80% of the converted capacity on a typical stop and keep the full figure as your worst case.

Fuel expands when it warms — am I getting less on a hot afternoon?

Slightly, in energy terms. Petrol expands by roughly a tenth of a percent per degree Celsius, so warm fuel contains marginally less energy per litre delivered. Canada requires retail dispensers to be temperature-compensated to a reference of 15 °C, and wholesale trade elsewhere corrects the same way. Most American and European retail pumps simply measure the volume that passes. Underground storage stays close to ground temperature all year, so the effect at the nozzle is far smaller than the forecourt-to-forecourt price spread.

What size are the spare fuel cans sold outside the US?

The standard metric can is 20 L, which is 5.28 US gallons, with 5 L and 10 L versions common for smaller loads. An American 5 gallon can holds 18.93 L, so it is noticeably smaller than the 20 L one it resembles on a shelf. Before you carry any of them, check the rules for the country you are in and for your ferry or tunnel operator, since several restrict or forbid spare fuel in a vehicle.