Estimate fuel cost, fuel needed, and cost per person for a one-way or round trip using your distance, fuel economy, and fuel price.
Advanced options
How to use our Fuel Cost Calculator
- Choose Units, then enter Trip distance, Fuel economy, and Fuel price in those matching units.
- Open Advanced options if needed and choose Trip type, enter People sharing fuel cost, and add Fuel use adjustment if traffic, hills, or cargo will change normal fuel use.
- Click Calculate to see Estimated fuel cost, Fuel needed, Total driving distance used, and Fuel cost per 100 distance.
- Sanity-check the result: if Adjusted fuel economy looks worse than expected in US mode or higher than expected in metric mode, review the Fuel use adjustment and make sure your units match the number you entered.
- If you are sharing the ride, use Fuel cost per person to split the total evenly.
Definitions
Trip distance: The one-way driving distance you enter before any round-trip doubling.
Fuel economy: How far the vehicle goes for a set amount of fuel. In US mode this is MPG, and in metric mode this is L/100 km.
Fuel price: The cost of one gallon in US mode or one liter in metric mode.
Fuel use adjustment: A percent change for real driving conditions. Positive values mean more fuel used than usual, and negative values mean less.
Adjusted fuel economy: The fuel economy after the fuel use adjustment is applied. In US mode, lower MPG means more fuel use. In metric mode, higher L/100 km means more fuel use.
Fuel needed: The estimated gallons or liters used for the trip.
Fuel cost per 100 distance: The fuel cost scaled to 100 miles or 100 km so trips are easier to compare.
Common mistakes and quick fixes
Mistake: Entering round-trip miles in Trip distance and also choosing Trip type as round trip.
Fix: Enter the one-way distance in Trip distance , then let Trip type double it.
Mistake: Using metric values while Units is still set to US, or using US values while Units is set to metric.
Fix: Match Units to your numbers before you calculate.
Mistake: Typing liters per 100 km into Fuel economy while US mode expects MPG.
Fix: In US mode, Fuel economy should be MPG. In metric mode, it should be L/100 km.
Mistake: Leaving Fuel price blank and expecting the calculator to treat it as 0.
Fix: Enter a real value in Fuel price . Blank is an error, but 0 is allowed if you are testing a special case.
Mistake: Entering 0 or a negative value for People sharing fuel cost .
Fix: Use a whole number of at least 1. If you are paying alone, enter 1.
Mistake: Using a very large positive Fuel use adjustment and then wondering why Adjusted fuel economy changed a lot.
Fix: Start with a small change like 5 or 10 and check whether the new Adjusted fuel economy feels realistic for your trip.
Limitations & Key Assumptions / Boundary Conditions
- This estimate covers fuel only. It does not include tolls, parking, wear and tear, charging stops, hotel costs, or food.
- Trip distance is treated as one way, then doubled only if Trip type is set to round trip.
- Fuel economy must already match the chosen Units: MPG for US or L/100 km for metric.
- Fuel use adjustment is a simple percent change. Real fuel use can also change with speed, traffic, hills, weather, tire pressure, cargo, and driving style.
- Fuel cost per person assumes an even split among everyone entered in People sharing fuel cost.
- If Fuel price is 0, the math still works, but that usually represents testing or a special case rather than normal driving.
- Very small distances can produce very small decimal costs and fuel amounts, which may not match how fuel is actually bought at a pump.
Methodology
Calculation steps
The calculator first finds the total driving distance used in the math. A one-way trip keeps your entered distance as-is, and a round trip doubles it.
effective_distance = distance * trip_multiplier
Next, it adjusts fuel economy if you enter a Fuel use adjustment. A positive adjustment means the vehicle uses more fuel than usual.
adjusted_mpg = base_mpg / (1 + adj_pct/100)
adjusted_L_per_100km = base_L_per_100km * (1 + adj_pct/100)
Fuel needed is then calculated from the adjusted fuel economy and the total distance.
fuel_used_gal = effective_distance_mi / adjusted_mpg
fuel_used_L = effective_distance_km * adjusted_L_per_100km / 100
Total fuel cost is fuel used times fuel price.
total_fuel_cost = fuel_used * fuel_price
If costs are shared, each person pays an equal part.
cost_per_person = total_fuel_cost / people_count
To help compare trips, the calculator also shows cost per 100 miles or 100 km.
cost_per_100 = total_fuel_cost / effective_distance * 100
Mini example
Suppose you choose US units, enter 120 for Trip distance, 30 for Fuel economy, 3.50 for Fuel price, and leave Trip type as one way. Fuel needed is 120 / 30 = 4 gallons. Total fuel cost is 4 x 3.50 = 14 dollars. Cost per 100 miles is 14 / 120 x 100 = 11.67 dollars per 100 miles.
Assumptions used in the math
The calculator assumes your fuel economy stays roughly steady across the trip after any adjustment you enter. In metric mode, L/100 km means liters used to travel 100 kilometers. The result is an estimate, so real fuel use can differ when road and driving conditions change.