Fuel Cost Calculator
Estimate fuel expenses for any trip distance and vehicle.
About the Fuel Cost Calculator
The Fuel Cost Calculator estimates the cost of a road trip or daily commute based on distance, vehicle fuel efficiency, and fuel price. Enter the trip distance in kilometers, the vehicle’s fuel consumption in liters per 100 km, and the local fuel price per liter — the tool returns the total fuel needed, the total cost, the per-kilometer cost, and the per-passenger split if you are carpooling.
Fuel efficiency is reported differently around the world. Most of the world uses liters per 100 kilometers (L/100km) — lower is better. The United States uses miles per gallon (mpg) — higher is better. The conversion is mpg = 282.48 / (L/100km). A typical passenger car rates 6-9 L/100km (33-39 mpg); a hybrid rates 4-5 L/100km (47-58 mpg); a large SUV rates 11-15 L/100km (16-21 mpg).
The calculator also estimates CO2 emissions. Burning one liter of gasoline releases approximately 2.31 kg of CO2 (per the US EPA’s greenhouse gas equivalencies calculator). A 450 km trip at 7.5 L/100km burns 33.75 liters and emits 77.96 kg of CO2. For context, the global average per-capita CO2 emission is around 4.5 tonnes per year.
The per-passenger split is useful for carpool cost-sharing. Splitting a $56 fuel cost four ways brings each passenger’s share to $14, much cheaper than train or plane for medium-distance trips. Some carpool apps (BlaBlaCar, Waze Carpool) compute this automatically; this tool does it manually so you can negotiate the split yourself.
How It Works
The core formula is: liters = (distance * efficiency) / 100, where efficiency is in L/100km. For a 450 km trip at 7.5 L/100km: liters = (450 * 7.5) / 100 = 33.75.
The cost is liters * price_per_liter. At $1.65/L, the cost is 33.75 * 1.65 = $55.69.
The conversion to US mpg uses mpg = 282.48 / (L/100km). The constant 282.48 comes from the unit conversion: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 liters, so 100 km = 100/1.609344 = 62.1371 miles and 1 L/100km = 3.785411784/62.1371 = 0.0609130 mpg-1, hence mpg = 1/0.0609130 / (L/100km) = 16.4134 / (L/100km)... but the more commonly cited conversion factor is 282.48, which uses Imperial gallons (4.54609 L). For US gallons, the correct factor is 235.215. The tool reports both.
The per-km cost is cost / distance. For the default trip: 55.69 / 450 = $0.124/km. Multiply by 100 for a per-100km cost ($12.39 here), useful for comparing fuel cost to per-km reimbursement rates.
The per-passenger split divides total cost by the headcount. The CO2 estimate multiplies liters by 2.31, the EPA factor for gasoline combustion. Diesel’s factor is 2.68 kg/L; for diesel vehicles, multiply by 2.68 instead.
Edge cases: a zero distance returns zero fuel and zero cost. A zero efficiency is rejected (would imply infinite fuel, which is impossible). The fuel price can be zero for free charging (EVs use a different calculation; see the EV section below).
Worked Examples
Default: 450 km, 7.5 L/100km, $1.65/L, 1 passenger. Fuel needed: 33.75 L. Total cost: $55.69. Per km: $0.124. CO2: 77.96 kg. This is roughly a 5-hour drive between major cities.
1200 km, 5.5 L/100km (hybrid), $1.40/L, 4 passengers. Fuel: 66 L. Cost: $92.40. Per passenger: $23.10. Per km: $0.077. A long-distance carpool that beats flying on cost.
20 km, 12 L/100km (large SUV), $1.80/L, 1 passenger. Fuel: 2.4 L. Cost: $4.32. A daily commute — multiply by 250 working days/year for an annual commute cost of $1,080.
800 km, 6.0 L/100km, $1.55/L, 2 passengers. Fuel: 48 L. Cost: $74.40. Per passenger: $37.20. Per km: $0.093. The per-km cost is the figure most employers use for mileage reimbursement — compare to your local tax authority rate.
100 km, 0 L/100km (EV, would need different math), $0/L. Cost: $0. The calculator returns zero, but a real EV uses about 15-20 kWh per 100 km; at $0.15/kWh, that is $2.25-$3.00 per 100 km.
When to Use This Tool
- Budgeting a road trip before booking hotels or committing to the drive vs. fly decision.
- Splitting fuel costs among carpool passengers for an equitable share.
- Comparing the per-km cost of owning vs. renting a car for a specific trip.
- Estimating annual commute cost from daily distance, fuel efficiency, and fuel price.
- Calculating mileage reimbursement for self-employed contractors and small-business owners.
- Comparing fuel cost against train, bus, or plane for medium-distance travel.
- Estimating the carbon footprint of a trip for sustainability reporting.
Limitations & Disclaimer
The calculator uses a constant fuel efficiency, which in real driving varies with speed, terrain, weather, and vehicle load — expect actual consumption to vary by 10-20% from the estimate. The CO2 factor (2.31 kg/L for gasoline, 2.68 kg/L for diesel) accounts for combustion emissions only; lifecycle emissions including extraction, refining, and transport add 20-30%. EVs use a different calculation based on kWh per 100 km. The tool does not model tolls, parking, wear-and-tear, or depreciation — for full cost-of-ownership analysis, use a dedicated TCO calculator. See our disclaimer for full terms.
Frequently Asked Questions
How do I convert L/100km to mpg?
For US gallons: <code>mpg = 235.215 / (L/100km)</code>. For Imperial gallons: <code>mpg = 282.48 / (L/100km)</code>. The tool reports both. A vehicle rated 7.5 L/100km gets 31.4 US mpg or 37.7 Imperial mpg.
Does the calculator account for city vs. highway driving?
No — it uses a single average efficiency. City driving typically uses 20-40% more fuel than highway driving due to stop-and-go traffic. For accurate estimates, look up the vehicle’s WLTP or EPA combined rating, which already weights city and highway. Many modern cars display real-time L/100km on the dashboard; use that figure for the most accurate estimate.
What is the CO2 emission factor for gasoline?
The US EPA uses 2.31 kg CO2 per liter of gasoline combustion (8.89 kg per US gallon). For diesel, the factor is 2.68 kg/L (10.16 kg/US gal). These figures account for the carbon content of the fuel and assume complete combustion. They do not include upstream emissions from extracting, refining, and transporting the fuel, which add roughly 20-30% to the total lifecycle emissions.
How do I calculate the cost for an electric vehicle?
EVs use kilowatt-hours (kWh) per 100 km instead of liters. A typical EV consumes 15-20 kWh per 100 km. Multiply by your electricity price (e.g. $0.15/kWh) for the cost per 100 km: <code>20 * $0.15 = $3.00/100km</code>. This tool does not model EVs directly; enter the equivalent L/100km if you want to use it.
What is the right fuel price to use?
Use the price at the stations you will actually stop at, not a national average. Fuel prices vary by 10-20% between brands and locations; highway stations often charge 5-10% more than city stations. For long trips, plan stops at cheaper stations using an app like GasBuddy (US) or GlobalPetrolPrices (international).
How accurate is the per-km cost estimate?
The estimate assumes a constant fuel efficiency, which is unrealistic in real driving. Real efficiency varies with speed (optimal is typically 70-90 km/h), terrain, weather, vehicle load, and tire pressure. For a 450 km trip, expect actual fuel consumption to vary by +/- 10% from the estimate. For annual budgeting, multiply the per-km cost by 1.1 to 1.2 as a safety margin.
Last updated: September 9, 2026 · Author: HT99 Tools Editorial Team