Fuel Cost Calculator: Trip, Commute & Carpool Cost

Q: How do I calculate fuel cost for a trip?

The math is straightforward: Cost=Fuel Needed×Price per unitCost = Fuel Needed × Price per unitCost=Fuel Needed×Price per unit. In metric, fuel (L) = distance ÷ 100 × L/100km. In imperial, fuel (gal) = distance ÷ MPG. Multiply by your local gas price to get the total. Round-trip? Just double the distance first.

Q: Why does speeding burn so much more fuel?

Air resistance grows with the square of speed. Pushing from 100 to 120 km/h (62 to 75 mph) can drop fuel economy by up to 20%, but on a 100 km drive you only save about 5 minutes. Most of the time the extra fuel cost outweighs the time gain.

Q: Should I idle or turn off the engine at a long red light?

If you’ll sit for more than ~10 seconds, turn it off. Restarting uses less fuel than idling that long. Cars with Stop-Start do this automatically; older ones need you to hit the key.

Q: Do low tire pressures really affect gas mileage?

Yes. Tires under-inflated by 5–10 PSI can add around 3% to fuel use. Rolling resistance goes up when the contact patch grows. Check pressure monthly when tires are cold—the sidewall number is the max, not the recommended fill.

Q: Is it better to use AC or roll down the windows?

Depends on speed. Under ~80 km/h (50 mph), open windows usually cost less than AC. Above that, the extra drag from open windows can outweigh the AC load. On the highway, close the windows and use AC.

Fuel Economy: What Actually Moves the Needle

Beyond the calculator—a few practical factors that most people overlook when planning trips or cutting commute costs.

Six Ways to Trim Fuel Costs

Slow down on the highway

Going 120 km/h instead of 100 km/h can cut economy by ~20%. You rarely save more than a few minutes. Ease off the throttle and watch the gauge.

Keep tires properly inflated

Under-inflation by 5–10 PSI adds ~3% to consumption. Check pressure when tires are cold, at least once a month.

AC vs. windows—speed matters

Low speeds: open windows cost less. Above ~80 km/h: the drag from open windows often beats the AC. Use AC on the highway.

Carpool when it fits

Splitting fuel with one other person cuts your cost in half. Commute projections show the yearly impact—carpooling can save hundreds.

Ditch extra weight

Every 50 kg (110 lbs) adds roughly 1–2% to fuel use. Roof racks and cargo boxes also hurt aero. Clear the trunk before long trips.

Avoid long idling

If you’re parked for more than ~10 seconds, shut the engine off. Restarting uses less fuel than idling. Stop-Start cars do this automatically.

Fuel Cost Calculator: Trip Cost, Commute Budget & Carpool Savings

Estimate road trip and commute fuel costs from distance, efficiency (L/100km or MPG), and gas price. How to calculate gas cost for a trip; fuel cost per km or per mile; carpool cost split; weekly and yearly commute projection; CO₂ emissions from fuel; tips to improve fuel economy.

What This Calculator Does

This fuel cost calculator estimates what you’ll spend on gas for a given trip or commute. Enter distance (km or miles), fuel efficiency (L/100km or MPG), and gas price; get total cost, fuel volume, and an efficiency score (Eco-Friendly, Moderate, Fuel-Heavy). The commute projection shows weekly, monthly, and yearly costs if you make that trip 5 days a week. Add passengers to see cost per person and savings vs. driving alone. A CO₂ estimate uses typical gasoline emissions (≈2.31 kg per liter, ≈8.89 kg per US gallon) so you can compare the carbon footprint of different routes or vehicles.

How Fuel Cost Is Calculated

The core formula is simple: Cost = Fuel Needed × Price. Fuel needed depends on units. Metric:

Fuel (L) = (distance in km ÷ 100) × L/100km

Imperial:

Fuel (gal) = distance in miles ÷ MPG

Round-trip doubles the distance before applying the formula. For example, 200 km at 8 L/100km needs 16 L; at $1.50/L that’s $24 for the round trip.

Efficiency Score: Eco-Friendly vs Fuel-Heavy

Metric (L/100km): Eco-Friendly ≤ 6, Moderate 6–10, Fuel-Heavy > 10. Imperial (MPG): Eco-Friendly ≥ 40 MPG, Moderate 25–40, Fuel-Heavy < 25. These buckets give a quick sense of how your car compares. A sedan at 7 L/100km lands in Moderate; a full-size SUV at 12 L/100km is Fuel-Heavy. The score doesn’t judge—it helps you plan budgets and compare vehicles.

Commute Cost and Carbon Footprint

If you drive the same trip 5 days a week, multiply the one-way cost by 5 for weekly, ~22 for monthly, and ~260 for yearly. That reveals the real budget hit of a long commute. The CO₂ badge estimates emissions from combusting gasoline: about 2.31 kg of CO₂ per liter (8.89 kg per US gallon). It’s an approximation—actual emissions depend on blend and driving conditions—but useful for comparing trips or vehicles.

Carpool and Cost Per Person

Enter the number of people splitting the cost—driver plus passengers. The calculator divides the total trip cost by that number. With 2 people, each pays half; with 4, a quarter. The savings vs. driving alone shows the percentage each person saves compared to paying the full amount solo.

Practical Tips That Actually Save Fuel

Speed matters: 120 km/h vs 100 km/h can cost ~20% more fuel but only shaves a few minutes off most trips. Tire pressure: 5–10 PSI low adds ~3% consumption. Weight: every 50 kg (110 lbs) adds 1–2%. AC vs. windows: low speeds favor windows; above ~80 km/h, AC is often more efficient. Idling: turn off the engine if you’ll wait more than ~10 seconds.

Fuel Cost Calculator FAQ

? How do I calculate fuel cost for a trip?

The math is straightforward:

\text{Cost} = \text{Fuel Needed} \times \text{Price per unit}

. In metric, fuel (L) = distance ÷ 100 × L/100km. In imperial, fuel (gal) = distance ÷ MPG. Multiply by your local gas price to get the total. Round-trip? Just double the distance first.

? Why does speeding burn so much more fuel?

Air resistance grows with the square of speed. Pushing from 100 to 120 km/h (62 to 75 mph) can drop fuel economy by up to 20%, but on a 100 km drive you only save about 5 minutes. Most of the time the extra fuel cost outweighs the time gain.

? Should I idle or turn off the engine at a long red light?

If you’ll sit for more than ~10 seconds, turn it off. Restarting uses less fuel than idling that long. Cars with Stop-Start do this automatically; older ones need you to hit the key.

? Do low tire pressures really affect gas mileage?

Yes. Tires under-inflated by 5–10 PSI can add around 3% to fuel use. Rolling resistance goes up when the contact patch grows. Check pressure monthly when tires are cold—the sidewall number is the max, not the recommended fill.

? Is it better to use AC or roll down the windows?