Use this Fuel Cost Calculator to estimate how much fuel a trip may use and how much that fuel may cost. Enter the travel distance, choose a fuel-efficiency format, enter the fuel price, and the calculator estimates fuel amount and trip cost.

The calculator supports common fuel-efficiency systems, including miles per US gallon, miles per UK gallon, kilometers per liter, and liters per 100 kilometers. It also supports fuel amount outputs in liters, US gallons, and UK gallons.

Important Note: This Fuel Cost Calculator estimates fuel amount and trip cost from distance, fuel efficiency, fuel price, and fuel unit. It supports mpg (US), mpg (UK), km/L, and L/100 km, plus fuel amount in liters, US gallons, and UK gallons.

The result is a planning estimate only. Actual fuel used and total cost can vary because of driving style, traffic, speed, weather, terrain, vehicle load, tire pressure, maintenance, idling, air conditioning, fuel type, fuel blend, route choice, and local pump prices.

Use this calculator for road-trip planning, commute cost checks, delivery estimates, route comparison, and fuel-budget planning. For business reimbursement, tax records, official mileage claims, fleet reporting, or accounting, verify distance, fuel price, fuel unit, mileage rate, receipts, and applicable policy before relying on the result.

Reviewed by: AjaxCalculators Editorial Team
Last updated: May 27, 2026
Method source: Standard distance, fuel-efficiency, and fuel-cost relationships
Editorial standards: AjaxCalculators Editorial Policy

What This Fuel Cost Calculator Calculates

This calculator estimates fuel needed and trip fuel cost from three inputs: distance, fuel efficiency, and fuel price.

• Distance: how far you plan to travel
• Fuel efficiency: how much fuel your vehicle uses, entered as L/100 km or mpg (US)
• Fuel price: the cost of fuel per liter or per US gallon

The calculator then estimates the amount of fuel required and the total fuel cost for the trip.

What Fuel Cost Means

Fuel cost is the estimated amount you will spend on fuel for a selected trip distance. It depends mainly on how far you drive, how efficiently your vehicle uses fuel, and the price of fuel.

A longer trip, lower fuel efficiency, or higher fuel price will increase the estimated fuel cost. A shorter trip, better fuel efficiency, or lower fuel price will reduce it.

Unit Constants Used by This Calculator

Item	Value	Use Note
1 mile	1.609344 km	Used when converting miles and kilometers.
1 US gallon	3.785411784 L	Used for mpg (US), US gallons, and price per US gallon.
1 UK gallon	4.54609 L	Used for mpg (UK), UK gallons, and price per UK gallon.
Fuel amount	Distance ÷ efficiency	Distance and efficiency must be interpreted in matching units.
Trip cost	Fuel amount × fuel price	The fuel amount unit and price unit must match.

How the Fuel Cost Calculator Works

1) Fuel Needed with L/100 km

If distance is entered in kilometers and fuel efficiency is entered as liters per 100 kilometers, the calculator estimates fuel needed like this:

Fuel needed (liters) = distance (km) × L/100 km ÷ 100

For example, if a trip is 300 km and the vehicle uses 7 L/100 km:

Fuel needed = 300 × 7 ÷ 100 = 21 liters

2) Fuel Needed with MPG

If distance is entered in miles and fuel efficiency is entered as miles per US gallon, the calculator estimates fuel needed like this:

Fuel needed (US gallons) = distance (miles) ÷ mpg

For example, if a trip is 240 miles and the vehicle gets 30 mpg:

Fuel needed = 240 ÷ 30 = 8 US gallons

3) Fuel Cost Formula

After fuel needed is calculated, the calculator multiplies the fuel volume by the fuel price.

Fuel cost = fuel needed × fuel price

If fuel needed is in liters, use the price per liter. If fuel needed is in US gallons, use the price per US gallon.

What This Fuel Cost Calculator Estimates

This calculator estimates the amount of fuel needed for a trip and the estimated fuel cost based on your entered values.

Input or Result	Meaning	Common Units
Distance	How far you plan to travel.	mi, km
Fuel efficiency	How much distance the vehicle travels per fuel unit, or how much fuel it uses per 100 km.	mpg (US), mpg (UK), km/L, L/100 km
Fuel amount	The estimated volume of fuel needed for the trip.	L, US gal, UK gal
Fuel price	The price of fuel per selected fuel unit.	per L, per US gal, per UK gal
Trip cost	The estimated fuel amount multiplied by fuel price.	Your entered currency
Step-by-step derivation	The calculation path used by the calculator.	Formula explanation

Fuel Cost Formula Summary

What You Want to Find	Formula	Use Note
Fuel used with mpg (US)	US gallons = miles ÷ mpg (US)	Use with fuel price per US gallon.
Fuel used with mpg (UK)	UK gallons = miles ÷ mpg (UK)	Use with fuel price per UK gallon.
Fuel used with km/L	Liters = kilometers ÷ km/L	Higher km/L means better fuel efficiency.
Fuel used with L/100 km	Liters = kilometers × L/100 km ÷ 100	Lower L/100 km means better fuel efficiency.
Trip cost	Cost = fuel amount × fuel price	The fuel amount unit and fuel price unit must match.
Miles to kilometers	km = mi × 1.609344	Used when converting distance units.
US gallons to liters	L = US gal × 3.785411784	Used for US gallon conversion.
UK gallons to liters	L = UK gal × 4.54609	Used for UK imperial gallon conversion.

Fuel Efficiency Units Explained

The calculator supports four common fuel-efficiency formats. Choose the one that matches your vehicle, country, fuel-economy record, or trip-planning source.

Fuel Efficiency Unit	Meaning	Better Direction	Example
mpg (US)	Miles traveled per US gallon.	Higher is better.	30 mpg (US)
mpg (UK)	Miles traveled per UK imperial gallon.	Higher is better.	36 mpg (UK)
km/L	Kilometers traveled per liter.	Higher is better.	14 km/L
L/100 km	Liters used per 100 kilometers.	Lower is better.	7 L/100 km

Do not enter L/100 km as mpg or mpg as L/100 km. These formats work in opposite directions: higher mpg is better, while lower L/100 km is better.

US Gallons vs UK Gallons

US gallons and UK imperial gallons are different fuel-volume units. This is why mpg (US) and mpg (UK) are not the same measurement.

Fuel Unit	Equivalent in Liters	Common Use
1 US gallon	3.785411784 L	United States fuel economy and fuel price contexts.
1 UK gallon	4.54609 L	UK imperial gallon contexts and some older fuel-economy references.

Because a UK gallon is larger than a US gallon, the same vehicle can show a higher mpg number in UK mpg than in US mpg even when the real fuel use is unchanged.

Unit Conversions Used by the Calculator

The calculator can work with kilometers, miles, liters, and US gallons by converting values when needed.

Conversion	Value
1 mile	1.609344 kilometers
1 kilometer	0.621371 miles
1 US gallon	3.785411784 liters
1 liter	0.264172 US gallons

These conversions help the calculator estimate fuel cost even when distance, efficiency, and price use different measurement systems.

Worked Example: Kilometers and L/100 km

Suppose you plan a 300 km trip. Your vehicle uses 7 L/100 km, and fuel costs $1.50 per liter.

Step 1: Calculate fuel needed
Fuel needed = distance × L/100 km ÷ 100

Step 2: Substitute the values
Fuel needed = 300 × 7 ÷ 100

Step 3: Calculate fuel volume
Fuel needed = 21 liters

Step 4: Calculate trip fuel cost
Fuel cost = 21 × 1.50

Step 5: Calculate the result
Fuel cost = $31.50

So, a 300 km trip at 7 L/100 km and $1.50 per liter would need about 21 liters of fuel and cost about $31.50.

Worked Example: Miles and MPG

Suppose you plan a 240-mile trip. Your vehicle gets 30 mpg, and fuel costs $3.75 per US gallon.

Step 1: Calculate fuel needed
Fuel needed = distance ÷ mpg

Step 2: Substitute the values
Fuel needed = 240 ÷ 30

Step 3: Calculate fuel volume
Fuel needed = 8 US gallons

Step 4: Calculate trip fuel cost
Fuel cost = 8 × 3.75

Step 5: Calculate the result
Fuel cost = $30.00

So, a 240-mile trip at 30 mpg and $3.75 per gallon would need about 8 gallons of fuel and cost about $30.00.

How to Use This Fuel Cost Calculator

1. Enter the trip distance.
2. Select the distance unit: mi or km.
3. Enter your fuel efficiency.
4. Select the fuel-efficiency unit: mpg (US), mpg (UK), km/L, or L/100 km.
5. Select the fuel amount unit you want to display: liters, US gallons, or UK gallons.
6. Enter the fuel price.
7. Select the matching fuel price unit: per liter, per US gallon, or per UK gallon.
8. Review the estimated fuel amount and trip cost.
9. Check the step-by-step derivation to confirm the formula path.
10. Use Refresh / Reset to clear the calculator and start again.

The calculator states that currency is not enforced. Enter the fuel price in your local currency and read the trip cost in the same currency.

Worked Example: Estimate Fuel Cost

Suppose you plan a 300-mile trip. Your vehicle gets 30 mpg (US), and fuel costs 3.50 per US gallon.

Step	Calculation	Result
Find fuel used	US gallons = 300 miles ÷ 30 mpg	10 US gallons
Find trip cost	Cost = 10 × 3.50	35.00
Optional liter conversion	Liters = 10 × 3.785411784	37.854 L

The estimated fuel cost is 35.00 in the currency used for the fuel price input.

How to Interpret the Result

Result	What It Means	Important Caution
Fuel amount	The estimated fuel volume needed for the entered trip distance.	Real fuel use may differ from the entered fuel-efficiency value.
Trip cost	The estimated fuel amount multiplied by fuel price.	It includes fuel only, not tolls, parking, maintenance, vehicle wear, or other trip expenses.
Fuel efficiency	The vehicle’s distance-per-fuel or fuel-per-distance value.	Make sure the selected unit matches the value you entered.
Fuel price	The price per liter, US gallon, or UK gallon.	The price unit must match the fuel amount unit used for cost calculation.
Step-by-step derivation	The formula path used by the calculator.	Use it to check distance conversion, efficiency conversion, fuel amount, and cost.

Fuel Cost vs Gas Cost

This page focuses on basic fuel cost: distance, vehicle efficiency, fuel price, fuel needed, and total trip cost.

Fuel cost can apply to gasoline, petrol, diesel, or other vehicle fuels when the same distance-efficiency-price relationship is used. The exact fuel type does not change the basic math, but it can change the price per liter or gallon and the vehicle’s real-world fuel efficiency.

If you need to split the cost between passengers, calculate the total fuel cost first, then divide it by the number of people sharing the trip.

Why Real Fuel Cost Can Vary

The calculator uses your entered distance, fuel efficiency, and fuel price. Real-world fuel cost can still vary because fuel economy and fuel prices are not fixed.

Factor	How It Can Affect Fuel Cost
Aggressive driving	Rapid acceleration, hard braking, and speeding can reduce fuel economy.
High speeds	Higher speeds can increase aerodynamic drag and reduce mpg.
Idling	Uses fuel without adding distance.
Cold weather and short trips	The engine may operate less efficiently before warming up.
Cargo, roof racks, and towing	Extra weight and aerodynamic drag can increase fuel use.
Air conditioning and accessories	Electrical and cooling loads can reduce fuel economy.
Terrain and road surface	Hilly, mountainous, or unpaved roads can increase fuel use.
Maintenance and tire condition	Poor tuning, tire pressure, alignment, or brake drag can reduce fuel economy.
Fuel price changes	Fuel price can vary by station, region, tax rate, grade, season, and market conditions.

Fuel Cost vs Total Trip Cost

This calculator estimates fuel cost only. A full trip budget may include other expenses.

Cost Type	Included in This Calculator?	Use Note
Fuel cost	Yes	Calculated from fuel amount × fuel price.
Tolls	No	Add toll-road, bridge, tunnel, or congestion charges separately.
Parking	No	Add parking fees separately.
Vehicle wear and maintenance	No	Fuel cost is not the same as total vehicle operating cost.
Insurance, depreciation, and registration	No	These are not included in fuel-only trip cost.
Food, lodging, and travel extras	No	Add travel expenses separately for full budgeting.
Passenger cost sharing	No, unless manually divided	This tool estimates total fuel cost; divide by passengers separately if needed.

Fuel Price Factors

Fuel prices can change by location and over time. The price you enter should match the fuel price you expect to pay for the trip.

Fuel Price Factor	Why It Matters
Crude oil price	Crude oil is a major part of gasoline cost and can change with global supply and demand.
Taxes and fees	Fuel taxes can vary by country, state, region, or city.
Refining costs and profits	Fuel formulation, refinery operations, and seasonal requirements can affect prices.
Distribution and marketing	Transport, station costs, local competition, and retail margins can affect pump prices.
Fuel grade	Regular, midgrade, premium, diesel, and alternative fuels may have different prices.
Local market conditions	Prices can differ between nearby stations and regions.

Tips for a More Accurate Fuel Cost Estimate

• Use your real-world fuel efficiency if you know it.
• Use the fuel price from your actual route, not only your local station.
• Use round-trip distance if you want the cost of going and returning.
• Add extra distance for detours, pickup stops, parking searches, or scenic routes.
• Use city fuel efficiency for stop-and-go trips and highway efficiency for long highway drives.
• Use a lower efficiency estimate if the vehicle is heavily loaded or towing.
• Check that the calculator is set to the correct fuel price unit: per liter or per US gallon.

Common Mistakes to Avoid

Mistake	Why It Causes Problems
Entering mpg (US) when the value is mpg (UK)	US and UK gallons are different sizes, so the fuel estimate changes.
Entering mpg as L/100 km	These units work in opposite directions and produce incorrect results if mixed.
Entering L/100 km as km/L	Lower L/100 km is better, while higher km/L is better.
Using price per liter with fuel amount in gallons	The fuel price unit must match the fuel amount unit.
Using one-way distance when planning a round trip	A round trip usually needs twice the one-way distance unless the return route differs.
Using highway mpg for city driving	City traffic, stops, and idling can reduce real-world fuel economy.
Ignoring traffic, terrain, or vehicle load	These can change real fuel use compared with the estimate.
Treating fuel cost as full trip cost	The calculator does not include tolls, parking, maintenance, or other travel expenses.
Forgetting that currency is not enforced	The calculator uses the number you enter; it does not convert currencies.

Formula Summary

What You Want to Find	Formula
Fuel needed using L/100 km	Liters = kilometers × L/100 km ÷ 100
Fuel needed using mpg	US gallons = miles ÷ mpg
Trip fuel cost	Fuel cost = fuel needed × fuel price
Miles to kilometers	Kilometers = miles × 1.609344
Kilometers to miles	Miles = kilometers × 0.621371
US gallons to liters	Liters = US gallons × 3.785411784
Liters to US gallons	US gallons = liters × 0.264172

Practical Uses

This Fuel Cost Calculator is useful for quick trip-cost and fuel-use estimates.

Use Case	How the Calculator Helps
Road-trip budgeting	Estimate expected fuel spend before a long drive.
Commute planning	Estimate weekly or monthly commuting fuel cost by repeating the trip distance.
Delivery planning	Estimate fuel cost for pickup, delivery, or courier routes.
Route comparison	Compare fuel cost between shorter and longer route options.
Vehicle comparison	Compare estimated fuel cost between vehicles with different fuel efficiency values.
Fuel price sensitivity	See how trip cost changes when fuel price rises or falls.
Travel reimbursement checks	Estimate fuel-only cost before applying official reimbursement rules.

When You May Need More Than This Calculator

This calculator is best for fuel-only estimates. You may need another tool or official method when the calculation requires live data, accounting rules, or full vehicle operating costs.

Need	Better Tool or Method
Live fuel prices	Use a current fuel-price app, station price board, or official price source.
Live route distance	Use a map or navigation tool with current route data.
Traffic-adjusted cost estimate	Use navigation data and realistic fuel economy for stop-and-go conditions.
Business reimbursement	Follow employer, tax authority, or reimbursement-policy rules.
Full vehicle operating cost	Add maintenance, tires, depreciation, insurance, parking, tolls, and other costs.
Electric vehicle travel cost	Use an EV cost calculator with kWh/100 km, miles/kWh, charging price, and charging losses.
Fleet reporting	Use recorded mileage, actual fuel purchase data, receipts, and fleet-management software.

Frequently Asked Questions

How do I calculate fuel cost for a trip?

Estimate the fuel amount needed, then multiply it by the fuel price. For example, if a trip uses 10 gallons and fuel costs 3.50 per gallon, the fuel cost is 35.00.

How do I calculate fuel used with mpg?

Divide distance in miles by miles per gallon. For example, 300 miles ÷ 30 mpg = 10 gallons.

How do I calculate fuel used with L/100 km?

Multiply distance in kilometers by L/100 km, then divide by 100. For example, 400 km × 7 L/100 km ÷ 100 = 28 liters.

How do I calculate fuel used with km/L?

Divide distance in kilometers by kilometers per liter. For example, 280 km ÷ 14 km/L = 20 liters.

Is mpg (US) the same as mpg (UK)?

No. A US gallon and a UK imperial gallon are different sizes, so mpg (US) and mpg (UK) are not the same measurement.

Why does L/100 km work differently from mpg?

L/100 km measures fuel used over a fixed distance, so lower is better. MPG measures distance traveled per gallon, so higher is better.

Does this calculator convert currencies?

No. Currency is not enforced. Enter the fuel price in your own currency and read the cost in that same currency.

Does the calculator include tolls or parking?

No. It estimates fuel cost only. Add tolls, parking, maintenance, and other trip expenses separately.

Why can my real fuel cost be different?

Real cost can differ because of traffic, speed, idling, weather, terrain, driving style, vehicle load, maintenance, fuel blend, and pump price changes.

References

1. FuelEconomy.gov — Many Factors Affect Fuel Economy
2. FuelEconomy.gov — Gas Mileage Tips: Driving More Efficiently
3. U.S. Energy Information Administration — Factors Affecting Gasoline Prices
4. NIST Guide to the SI — Appendix B.9: Conversion Factors by Quantity
5. NIST — Approximate Conversions from U.S. Customary Measures to Metric

Related Calculators

• Gas Cost Calculator
• Mileage Calculator
• Electricity Cost Calculator
• Car Finance Calculator
• Loan Calculator
• Percent Off Calculator
• Sales Tax Calculator
• Time Calculator

Fuel Cost Calculator Disclaimer

This Fuel Cost Calculator provides planning estimates only. It estimates fuel amount and trip cost from the distance, fuel-efficiency value, fuel price, and units entered by the user.

Actual fuel use can vary because of traffic, speed, acceleration, braking, idling, weather, terrain, road surface, route choice, vehicle load, towing, roof racks, tire pressure, maintenance, air conditioning, fuel type, fuel blend, and driving conditions. Actual fuel price can vary by station, location, taxes, fuel grade, market conditions, and date.

This calculator estimates fuel cost only. It does not include tolls, parking, maintenance, tires, depreciation, insurance, registration, repairs, lodging, meals, driver pay, tax rules, reimbursement policies, or full vehicle operating cost. For official claims, business accounting, fleet reporting, or tax records, use actual receipts, official mileage records, and the applicable policy or professional guidance.