Calculate MPG, liters per 100 kilometers, kilometers per liter, and cost per mile in one place. Enter odometer readings or fuel used to measure your real-world fuel economy in seconds.
This gas mileage calculator with fuel cost works best when you use numbers from a full tank to the next full tank. That method gives you a reliable view of your real fuel economy instead of a rough guess.
Enter your current and previous odometer readings, or use the trip miles you drove. Subtracting the readings gives you the exact trip distance.
Type in the gallons or liters you used to refill the tank. If you know the pump price, add that too so the calculator can estimate cost per mile and total fuel spend.
You will see miles per gallon, fuel consumption in liters per 100 kilometers, kilometers per liter, and optional cost numbers. Use those results to compare trips, vehicles, and driving habits.
If you want the most useful answer, avoid mixing partial fill-ups with guesswork. Fill the tank, reset your trip meter or note the odometer, drive normally, then fill the tank again. The gallons used on the second fill-up tell you how much fuel the vehicle consumed over that trip distance.
You can switch between US and metric units without changing the way you drive. In the US, people usually track miles per gallon. In many other places, drivers look at liters per 100 kilometers. Both show the same fuel consumption story from different angles.
Look past one MPG number. These quick result checks help you turn fuel economy data into useful driving and budgeting decisions.
Higher MPG means your vehicle travels farther on the same amount of gas. Use this number when you compare vehicles, routes, or driving habits.
Lower L/100km means lower fuel consumption. This format is useful when you want a direct fuel-used-over-distance view.
km/L gives you another easy distance-per-fuel measure. It can be helpful when comparing imported vehicles or international data.
When you add pump price, you see how much each mile or kilometer really costs. This is valuable for commuting and business mileage.
One tank can swing because of weather or traffic. Track several fill-ups to spot real changes in fuel efficiency.
The projection table estimates fuel needed over common trip distances so you can budget before you leave home.
If you want to know how to calculate gas mileage manually, you only need a trip distance and the amount of fuel used.
MPG = miles driven / gallons used
To find miles driven from odometer readings, use:
miles driven = current odometer - previous odometer
L/100km = 235.215 / MPG
km/L = MPG x 0.425144
These conversions let you compare fuel consumption across countries, vehicle reviews, and manufacturer data sheets.
total fuel cost = gallons used x price per gallon
cost per mile = total fuel cost / miles driven
From 18,420 to 18,732 miles, you drove 312 miles. If you used 11.4 gallons, your gas mileage is 27.37 MPG.
Divide 235.215 by 27.37 to get about 8.59 L/100km, then use the automatic conversions to compare unit systems.
At $3.79 per gallon, 11.4 gallons costs $43.21. Divide that by 312 miles and your cost per mile is about $0.1385.
You can use a fuel efficiency calculator for much more than checking one tank of gas. These real examples show how drivers use MPG and cost-per-mile numbers in everyday decisions.
Suppose your round-trip commute is 42 miles and your car averages 31 MPG. You use about 1.35 gallons per workday. At $3.65 per gallon, that commute costs about $4.93 per day in fuel. Over 22 workdays, fuel alone is roughly $108.46. That number helps you set a realistic monthly transportation budget.
If you plan to drive 860 miles and your SUV gets 24 MPG, you will need about 35.83 gallons of gas. At $3.89 per gallon, fuel cost is about $139.37. That estimate lets you compare routes, split costs with friends, and decide whether slower highway speeds are worth the time.
Imagine your sedan usually returns 33 MPG, but your last three tanks averaged 28 MPG. That 5 MPG drop is a real warning sign when the same route and weather stay similar. Low tire pressure, a dirty air filter, dragging brakes, or repeated short trips can all raise fuel consumption and deserve a closer look.
Vehicle A gets 22 MPG and Vehicle B gets 31 MPG. On 15,000 miles a year, Vehicle A uses about 681.82 gallons while Vehicle B uses about 483.87 gallons. At $3.70 per gallon, the more efficient car saves about $732.41 per year on fuel. That is a stronger buying metric than MPG alone because it turns efficiency into dollars.
A driver covers 1,240 miles in a week and burns 46.8 gallons. That works out to 26.50 MPG. If gas averaged $4.05, weekly fuel expense is $189.54 and cost per mile is about $0.153. Numbers like these help small businesses price routes, review reimbursement rates, and understand whether a vehicle is profitable to operate.
Simple habits can improve highway MPG and city efficiency. Keep tires at the recommended pressure, remove heavy cargo you do not need, combine short errands into one trip, avoid long idle time, and accelerate smoothly. If your current result is 24 MPG, even a jump to 26 MPG reduces annual fuel use in a meaningful way.
One of the biggest content gaps on many gas mileage pages is the difference between fuel economy and fuel consumption. Understanding that difference helps you read your results more clearly.
MPG is helpful, but equal MPG gains do not always create equal savings. Going from 15 MPG to 20 MPG saves much more fuel than going from 35 MPG to 40 MPG over the same annual miles. That is why some analysts call this the MPG illusion. A change in fuel consumption is often easier to understand when you translate the result into gallons used per year or liters per 100 kilometers.
Liters per 100 kilometers directly tells you how much fuel the vehicle burns over a fixed distance. If one car uses 9.5 L/100km and another uses 7.2 L/100km, the lower number is clearly more efficient. That makes it easier to compare fuel consumption across test reports, international specs, and mixed fleets.
Over 12,000 miles per year, a vehicle at 15 MPG uses 800 gallons. Improve that to 20 MPG and fuel use drops to 600 gallons, a savings of 200 gallons. Over the same 12,000 miles, improving from 30 MPG to 35 MPG cuts fuel use from 400 gallons to about 342.86 gallons, a savings of only 57.14 gallons. The MPG gain is 5 in both cases, but the fuel savings are not close.
If you are shopping for a vehicle, compare MPG, annual gallons used, and yearly fuel cost at your expected miles driven. In states where gas prices run high, such as California, the dollar difference between two vehicles can grow faster than you expect. In lower-price markets such as Texas, the savings may still be meaningful, but the payback period on a more efficient model can look different. The same calculator result becomes much more useful when you connect it to local fuel price and yearly miles.
Keep planning after you calculate your MPG. These LiteCalc tools can help with trip costs, fuel budgeting, and day-to-day number crunching.
Estimate trip fuel expense from miles driven, vehicle efficiency, and current pump prices.
Count days between fill-ups, service visits, mileage logs, or trip dates with a simple calendar tool.
Work through MPG conversions, trip estimates, and percentage changes when you want to check the math manually.
Compare commuting fuel expense against hourly, weekly, or annual pay when you plan a work schedule or new job.
Measure the value of grocery rewards, warehouse memberships, or gas station discounts against your actual fuel spend.
Convert fuel budgets and travel costs when you compare US road trip spending with prices in other countries.
Common questions about MPG, fuel consumption, and cost per mile
Subtract your previous odometer reading from your current reading to find trip distance, then divide that distance by the gallons of fuel used. If you drove 312 miles and used 11.4 gallons, your gas mileage is 27.37 MPG.
Fill your tank, record the odometer, drive normally, then record the odometer again at the next fill-up. Subtract the two readings for miles driven and divide by the gallons needed to refill the tank.
A good MPG depends on the vehicle type. Many compact cars land above 30 MPG, midsize sedans often fall in the mid-20s to low-30s, SUVs usually range from the high teens to the upper 20s, and full-size trucks are often lower.
EPA numbers come from controlled tests. Real-world MPG can be lower because of traffic, cold starts, short trips, hills, wind, underinflated tires, cargo weight, and faster highway speeds.
Divide 235.215 by MPG to convert miles per gallon to liters per 100 kilometers. For example, 30 MPG equals about 7.84 L/100km.
Divide the distance by your vehicle's MPG. At 25 MPG, a 300-mile trip uses 12 gallons. At 35 MPG, the same trip uses about 8.57 gallons.
Usually no. Premium fuel only helps if your vehicle's engine is designed or tuned to need higher octane. For most regular-fuel vehicles, premium gas raises cost without improving MPG.
Start with tire pressure, smoother acceleration, lower highway speeds, less idling, lighter cargo, and up-to-date maintenance. Small changes in speed and driving style can noticeably reduce fuel consumption.