GasBuddy trip calculator: check your fuel budget
Three numbers decide what a drive costs in fuel: distance, how much fuel your vehicle uses, and the price you pay. Any trip cost calculator, GasBuddy’s or ours, just multiplies them. The result is only as good as those inputs, and fuel economy is the one most people get wrong. The fuel cost calculator on this page works in litres or US gallons and runs entirely in your browser.
What to enter in GasBuddy’s calculator
GasBuddy’s official instructions ask for a starting point, destination, one-way or round trip, US or metric units, vehicle details and fuel type. If your vehicle isn’t listed, the instructions describe entering city and highway fuel economy and tank size yourself. The calculator page also lists an optional stop and fuel types including regular, midgrade, premium, diesel and E85.
Check the trip type before you calculate. If the distance you entered already covers the return journey, don’t double it again. The same applies to our calculator’s “Double the distance for a return trip” box.
People searching for a “GasBuddy trip planner” usually mean one of two things. The Trip Cost Calculator estimates the fuel bill. Finding stations to stop at along the way is a separate app feature, Search Along Route, covered in our GasBuddy map guide.
Metric calculation
Litres needed = distance in km × L/100 km ÷ 100. Multiply litres by the price per litre to estimate fuel spending.
For an illustrative 300 km journey at 7.5 L/100 km, consumption is 22.5 litres. At C$1.60/L, estimated fuel cost is C$36.00. A 600 km return trip under the same assumptions costs C$72.00.
US calculation
US gallons needed = miles ÷ miles per US gallon. Multiply by the price per US gallon.
A hypothetical 250-mile journey at 30 mpg uses about 8.33 US gallons. At US$3.50/gallon, estimated cost is US$29.17. Don’t substitute Canadian cents per litre into this formula.
The mpg trap: US versus imperial
A fuel economy figure in “mpg” might use US gallons or imperial gallons, and the gap is big: 1 imperial gallon equals 1.2 US gallons. Natural Resources Canada gives the conversions as L/100 km = 235.21 ÷ mpg (US) and L/100 km = 282.48 ÷ mpg (imperial). Source: NRCan, understanding the tables.
| Figure you have | Converted | What it means |
|---|---|---|
| 30 mpg (US) | 235.21 ÷ 30 = about 7.84 L/100 km | Matches US ratings and US pumps |
| 30 mpg (imperial) | 282.48 ÷ 30 = about 9.42 L/100 km | Uses about 20% more fuel than 30 US mpg |
If you take an imperial figure from an older Canadian or British source and enter it as US mpg, your estimate will come out too low. When in doubt, use L/100 km in metric mode, since that’s what Canadian ratings use.
Get a real fuel economy number
The rating on the window sticker is a lab figure. fueleconomy.gov notes that results vary between drivers, and a few drivers see a marked deviation from the EPA estimates. Source. Your own number is better. To measure it:
- Fill the tank and note the odometer.
- Drive normally until your next fill-up, then fill the tank again.
- Divide the litres you just bought by the kilometres driven, and multiply by 100.
For example, 41.2 L after 520 km works out to about 7.9 L/100 km. Do this over a few tanks and you have a figure that reflects your car and your roads. Our fuel logbook does the arithmetic and stores it on your device.
What pushes fuel use up on a trip
These factors come from the US government’s fueleconomy.gov:
- Speed. Gas mileage usually decreases rapidly above 50 mph (about 80 km/h). Source
- Aggressive driving. Speeding, hard acceleration and hard braking can lower mileage by roughly 15% to 30% at highway speeds. Source
- Roof cargo. A large, blunt roof-top cargo box can cut fuel economy by about 6% to 17% on the highway, and 10% to 25% at 65 to 75 mph. Source
- Cold weather. A conventional gasoline car can expect a 10% to 20% loss in city driving, and 15% to 33% on short trips. Source
- Towing and heavy loads. Towing a trailer or carrying excessive weight decreases fuel economy. Source
Budget for uncertainty
| Metric scenario (hypothetical) | Distance | Consumption | Fuel price | Estimated cost |
|---|---|---|---|---|
| Base example | 300 km | 7.5 L/100 km | C$1.60/L | C$36.00 |
| Roof box, 10% worse | 300 km | 8.25 L/100 km | C$1.60/L | C$39.60 |
| Winter driving, 15% worse | 300 km | 8.625 L/100 km | C$1.60/L | C$41.40 |
| Higher consumption | 300 km | 9 L/100 km | C$1.60/L | C$43.20 |
| Higher price | 300 km | 7.5 L/100 km | C$1.75/L | C$39.38 |
These rows show which assumptions move the budget most. They aren’t forecasts or live prices. Here, a 20% jump in consumption costs more than a 15-cent jump in price, which is why a realistic fuel economy number matters more than finding the perfect price estimate.
A cheaper station can increase total cost
Work out the gross saving on the fuel you’ll buy, then subtract the fuel used for the extra distance to reach the cheaper station. Add tolls or other charges if they apply. Keep your time separate so you can decide what it’s worth. The GasBuddy near me guide has worked examples and a break-even distance rule.
Is the GasBuddy trip calculator available for Canada?
Its instructions include a choice of US or metric units, so you can work in kilometres and litres. Source. Whatever calculator you use, make sure the price is per litre in metric mode and per US gallon in US mode. If you’re crossing the border, convert prices first with the fuel price converter.
What if the GasBuddy trip calculator is not working?
Fuel Route Guide can’t fix GasBuddy’s tools, but a few checks help. Re-enter the start and destination, confirm the trip type and units, and if your vehicle doesn’t appear, enter fuel economy and tank size manually as GasBuddy’s instructions describe. If it still fails, use GasBuddy’s help centre. As a backup, take the distance from any map and use the calculator below.
How do I estimate fuel cost when towing a trailer?
There’s no reliable universal percentage, because trailer weight, shape and speed all matter. fueleconomy.gov says only that towing decreases fuel economy. Source. The most honest input is your own: log a tank or two while towing in the fuel logbook, then enter that L/100 km or mpg here. Before a long tow, it’s also worth running a vehicle recall check.
Is a calculator built into this page?
Yes. Use the independent trip fuel calculator below to estimate a fuel budget in metric (km, L/100 km, C$/litre) or US units (miles, mpg, US$/gallon). Tick the return-trip box to double the distance. The starting values are hypothetical examples, not live prices, and the calculation runs in your browser. It isn’t GasBuddy’s calculator. Start at GasBuddy for its own tools.
Related guides
- GasBuddy near me: nearby fuel decisions
- GasBuddy map guide: stations along your route
- Fuel logbook
- Fuel price converter
- Canadian units and locations
- Costco detour examples
Fuel Route Guide is an independent publication and is not affiliated with GasBuddy. Examples use hypothetical prices.
Source research: . This is a research date, not a pump-price observation. Written and reviewed by Shehan Chamudith Udakumbura. Read our editorial policy.