Fuel Cost Calculator: Trip, Commute & Monthly Budget
Estimate what a single trip, your daily commute or a whole month of driving costs in fuel, with tolls and parking added when you need them. Enter the economy in MPG, km/L or L/100 km
Choose what to estimate: your daily commute, the total distance of a month, or a single trip.
Add your car's fuel economy, your local fuel price, and the type of driving you mostly do (city, highway, or mixed).
Get an instant breakdown: the cost of the month or trip, fuel needed, and cost per km or mile — updated live as you type.
Driving & Fuel
This is a planning estimate. Real consumption on the road depends on the car’s age and condition, tire pressure, load, weather, terrain and how you drive, so your actual cost can be higher or lower.
How to use this tool
- Choose Miles & Gallons or Km & Liters, then pick what to estimate: a daily commute, a monthly total or a single trip.
- Enter the distance (and the driving days for a commute or a month), your car's average fuel economy and the local fuel price. For a single trip you can add tolls and parking.
- Pick the driving profile that matches your routes: heavy city, mixed, highway, or sporty and loaded.
- Read the cost, the fuel volume and the cost per 100 miles or km. In Km & Liters the economy can be entered as km/L or L/100 km.
Worked example
At 25 miles a day over 22 driving days, you cover 550 miles. At 28 MPG that needs 19.6 gallons, which at 3.50 a gallon costs 68.75 a month, or 3.13 per driving day, with 12.50 per 100 miles. Switching the profile to heavy city driving multiplies the fuel by 1.15, so the same month needs about 22.6 gallons and costs roughly 79.06. The profile factors (+15%, −12%, +20%) are rough planning adjustments, not measurements, so replace the economy figure with your own tank-to-tank average if you have one.
Methodology
Internal combustion engine fuel efficiency is governed by the engine's Brake Specific Fuel Consumption (BSFC), aerodynamic drag, and tractive rolling resistance. This calculator divides your monthly distance by your fuel economy, adjusted by the driving-profile factor you pick (for example ×1.15 for heavy city traffic), then multiplies the fuel volume by your fuel price. For a single trip the same arithmetic applies to the trip distance: fuel volume = distance ÷ economy (or distance × value ÷ 100 when you enter L/100 km), and the total is that volume times the price plus the tolls and other costs you add. The real cost per unit is the total divided by the distance.
Same car, same month, four driving profiles
Inputs for every row: 800 km in the month, a base economy of 14 km/L and fuel at 1.50 per liter (any currency).
| Driving profile | Fuel needed | Monthly cost | Cost per 100 km |
|---|---|---|---|
| Combined (×1.00) | 57.1 L | 85.71 | 10.71 |
| Heavy city (×1.15) | 65.7 L | 98.57 | 12.32 |
| Highway (×0.88) | 50.3 L | 75.43 | 9.43 |
| Sporty or loaded (×1.20) | 68.6 L | 102.86 | 12.86 |
How to read it: the tool divides your economy by the profile factor, so a higher factor means more liters for the same distance. The gap between highway and sporty is 27.43 for the month, from the same car and route length. The factors (+15%, −12%, +20%) are rough planning adjustments, not measurements of your vehicle, so replace 14 with your own tank-to-tank average and treat the table as a budgeting guide only.
Clara's wedding trip: drive alone, or with three friends?
Clara has to get to a wedding 240 km away and back. Her car averages 6.4 L/100 km, fuel is 1.92 per liter, and she expects 18.50 in tolls and 12.00 for parking. The rail quote she found is 31.00 per person.
- Set distance 480 km (both ways) and efficiency 6.4 L/100 km. Fuel needed: 480 × 6.4 ÷ 100 = 30.72 L.
- At 1.92 per liter, fuel-only cost is 58.98.
- Add 18.50 + 12.00 of extras: total trip cost 89.48, a real cost of 0.19 per km.
- Alone, that is 89.48 against 31.00 by rail, so the train wins. With three friends splitting it, 89.48 ÷ 4 = 22.37 each (the tool does not split by person, so divide by hand), which beats the rail quote.
She also tries a price of 2.10 per liter: the total becomes 95.01, or 23.75 each. The decision holds, but the margin shrinks. This ignores wear, depreciation and insurance, so treat it as a fuel-and-fees comparison.
Automotive Fuel Efficiency & Diagnostic Essentials
A code reader, a tire inflator and a phone mount. Correct tire pressure is one of the simple checks that affect consumption.
ANCEL AD310 Universal OBD II Car Engine Fault Code Reader
An OBD-II code reader that shows live sensor data and engine fault codes, according to the listing.
AstroAI L7 Portable Air Compressor & Tire Inflator 150 PSI
Underinflated tires increase rolling resistance and can waste fuel (up to about 3%, according to the US DOE). Its digital auto-stop helps you inflate accurately anywhere.
Miracase Universal Air Vent Car Phone Mount with Metal Hook
An air-vent phone mount with a metal hook, according to the listing, to keep navigation in view while you drive.
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Frequently asked questions
Why does my car consume more fuel than the manufacturer's window sticker indicates? ▼
Official manufacturer ratings (WLTP or EPA) are measured under controlled laboratory dynamometer conditions without strong headwinds, cargo weight, tire degradation, or aggressive overtaking. In daily driving, cold engine starts, elevation changes, air conditioning, and traffic congestion can make real-world economy noticeably worse than the rated figure, by an amount that varies a lot between cars and trips.
How does vehicle age impact real fuel consumption? ▼
As an engine ages, carbon deposits on intake valves, worn spark plugs, degraded oxygen (O2) sensors, and clogged fuel injectors can cause incomplete combustion. A poorly maintained older vehicle can burn noticeably more fuel than it did when new; regular servicing helps limit this.
How does tire pressure affect my monthly gas bill? ▼
Under-inflated tires flex more and create greater rolling resistance. The US Department of Energy (fueleconomy.gov) estimates that keeping tires at the manufacturer's recommended pressure can improve fuel economy by up to about 3%.
How do I convert between km/L and liters per 100 km (L/100 km)? ▼
To convert km/L to L/100km, divide 100 by your km/L figure (e.g., 100 ÷ 12.5 km/L = 8.0 L/100km). Conversely, 100 ÷ L/100km yields km/L.
Can you show how the monthly cost is worked out? ▼
Suppose you drive 1,000 km a month at 12.5 km/L with fuel at 1.60 per liter. Fuel is 1,000 / 12.5 = 80 L, so the monthly cost is 80 × 1.60 = 128.00, or 12.80 per 100 km. Choosing Heavy City divides the economy by 1.15, so fuel becomes 1,000 / (12.5 / 1.15) = 92 L and the cost 147.20. Highway uses 0.88, which gives 70.4 L. In daily mode the monthly distance is the daily distance times the driving days, and the days field only changes the daily averages, not the monthly total.
Does mpg mean the same everywhere, and how do I convert it? ▼
No. A US gallon is 3.785 liters and an imperial (UK) gallon is 4.546 liters, about 20% larger, so the same car shows a higher mpg figure in UK units. Enter mpg that matches the gallon size of the price you type. To convert US mpg to liters per 100 km, divide 235.215 by the mpg: 30 mpg is about 7.8 L/100 km. Without a fuel economy figure above zero, the cost cells show a dash. The driving-profile factors are rough adjustments, not measurements of your own car.
Why is the “Real Cost” higher than “Fuel Cost Only”? ▼
If you add extra costs (like tolls, parking or a maintenance share for the trip), they are spread across the distance driven, which raises the real cost of every km or mile.
Which fuel efficiency figure should I enter? ▼
The calculator applies the single efficiency value you type to the entire distance. Real consumption changes with speed, traffic, load and weather, so a brochure figure may understate your cost. For a more realistic estimate, enter an average from your own fill-ups, and remember that L/100 km works in reverse to MPG and km/L: lower is better.