Road trip gas cost in Canada: how to calculate it, with two examples

Before any road trip, the same question comes up: how much will the gas cost? Working out your road trip gas cost takes one line of math, and it's more reliable than many online calculators, because you plug in your own numbers. Here's the method, two full examples, and what station prices along Highways 20, 40 and 401 show.

The road trip gas cost formula

Cost = distance (km) ÷ 100 × fuel consumption (L/100 km) × price ($/L)

So you need three numbers:

1. The distance. Use your navigation app, address to address. For a round trip, double it.
2. Your fuel consumption. On the highway, use your vehicle's "highway" rating. NRCan's fuel consumption ratings↗ (opens in a new tab) give three values: city, highway and combined. According to NRCan's guide to understanding the tables↗ (opens in a new tab), the highway rating represents a mix of open highway and rural roads typical of longer trips. If you keep a fill-up log, your own average is even better.
3. The price per litre. The price where you'll actually fill up, not the one near home.

Quick example: 300 km at 7 L/100 km and $1.90 a litre comes to 300 ÷ 100 × 7 × 1.90 = $39.90.

Example 1: Montreal to Quebec City, by Highway 20 or 40

According to OpenRouteService (the routing engine Gazo uses for its drive times), it's 252.9 km from downtown Montreal to downtown Quebec City on Highway 20, and 266.7 km on Highway 40. For the price, we used the median of Quebec City stations, averaged from October 4 to 6, 2026: 191.1¢/L.

Highway 40 burns 0.9 L more in the Kona, or $1.77 at that price: the choice is really about traffic and scenery. The round trip on Highway 20 in a Kona comes to $64.76.

Where to fill up between Montreal and Quebec City

This is where you can really save. In Quebec, every station reports its price to the Régie de l'énergie, the provincial energy board, and Gazo logs every change. We calculated the median price of regular in towns along both highways, from Sunday, October 4, 2026 at 8 a.m. to Tuesday, October 6 at 4 p.m., and compared it with Montreal's.

Those three days fell in the middle of a series of price hike waves in Montreal, which widens the gaps. Over a longer period, they're smaller, but they point the same way. According to the daily averages published by the Régie de l'énergie↗ (opens in a new tab) (in French), from January 5 to August 31, 2026, regular cost on average:

• 10.0¢ less than in Montreal in the Les Maskoutains area (Saint-Hyacinthe), cheaper on 161 of 169 business days;
• 8.0¢ less in the Drummond area and 8.1¢ less in the D'Autray area (Berthierville);
• 5.7¢ less in Quebec City, 5.2¢ less in Lévis and 4.4¢ less in Trois-Rivières.

The plan: leave Montreal with a fairly low tank and fill up in Saint-Hyacinthe or Drummondville on Highway 20, or near Berthierville and in Trois-Rivières on Highway 40. On 40 litres, 10¢ less per litre is $4. Not worth a 20 km detour, but a nice saving if the station is right off the exit.

Example 2: Montreal to Toronto gas cost, on Highways 20 and 401

OpenRouteService puts it at 549.3 km from one downtown to the other. In a Kona (6.7 L/100 km), that's 36.8 litres. What they cost depends a lot on where you buy them. According to NRCan's average prices by city↗ (opens in a new tab), for the week of September 23 to 29, 2026:

Ontario taxes gas less, and it shows: a 23.1¢ gap between Montreal and Kingston that week. We explain why in why gas is more expensive in Quebec. The smart move on the 401, heading west: cross into Ontario with enough to get you there, then fill up, for example in Kingston, about halfway. Heading east to Montreal, do the opposite: fill up in Ontario before you cross. Outside Quebec, Gazo's prices come from drivers or, failing that, an official estimate for the area, always labelled as such.

Three mistakes that drive up the bill

• Driving at 120 instead of 100. According to NRCan's fuel-efficient driving techniques↗ (opens in a new tab), a vehicle uses about 20% more fuel at 120 km/h than at 100 km/h. On Montreal to Toronto in a Kona, that's about 7.4 more litres, close to $13 at the Kingston price.
• Using the combined rating for a highway trip, or the reverse. In the city, the Kona goes up to 8.4 L/100 km, 25% more than on the highway.
• Forgetting the roof box and the load. Wind and weight add up: the details are in our 12 ways to use less gas.

And if a wave of price hikes hits the day before you leave, fill up before the stations near you follow: here's what to do when gas prices are going up.

Planning your fill-ups with Gazo

Gazo doesn't have a trip planner, and we'd rather tell you upfront. But on the road, the app sorts the stations around you by price, within 5, 10 or 25 km, and "Go" opens Google Maps, Waze or Apple Maps straight to the station you pick, with the drive time and distance. Before you leave, the city pages on our site show prices in the towns on your way. The full picture is in how Gazo works.