312 mi on 9.8 gal is 31.8 mpg, the same as 38.2 UK mpg, 7.39 L/100 km, or 13.54 km/L. The fuel cost $43.90, $0.141 per mile.
Fuel cost per 100 mi at $4.48 per gallon
계산 방법 S
Distance since the last fill-up
24,812−24,500=312mi
Distance per unit of fuel
9.8gal312mi=31.8367mi/gal
Convert to the other units
US mpg=9.8gal312.00mi=31.84,L/100 km=502.12100×37.097=7.39
1 mi = 1.609344 km, 1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L (exact, NIST SP 811).
Fuel cost
9.8×4.48=43.90;312mi43.90=0.1407per mi
CO₂ from the fuel
9.8gal×8,887g/gal÷1000=87.1kg
EPA emission factor for gasoline.
Gas mileage calculator (MPG calculator) 소개
Fuel economy is the distance driven divided by the fuel it took to refill the tank. Enter the odometer reading at your last fill-up and today's, or the trip distance, and the gallons or liters you just added. The result is shown as US mpg, UK mpg, L/100 km and km/L, with the fuel cost per mile and per kilometer and the CO₂ the fuel released.
With the defaults, 312 miles on 9.8 gallons is 31.8 mpg. At $4.48 a gallon, the US average for regular in the week of 21 September 2026 (EIA), that tank cost $43.90, or 14.1 cents a mile. The fill-up log takes one line per fill-up and gives the average over all of them, each tank's figure and a trend line.
The method assumes you fill to the same level each time, since a partly filled tank makes one reading high and the next one low. The average of a log is total miles over total fuel, which is not the same as averaging the per-tank mpg.
계산 예제
312 miles on 9.8 US gallons at $4.48
Calculate from
One fill-up
Distance in
마일
Fuel in
미국 갤런
Distance from
Odometer readings
Odometer at last fill-up
24,500
Odometer now
24,812
Fuel added to refill the tank
9.8
Fuel price per gallon or liter
4.48
Fuel economy (US)
31.8 mpg
Fuel economy (UK)
38.2 mpg
Fuel consumption
7.39 L/100 km
Kilometers per liter
13.54 km/L
Fuel cost
43.90
Cost per mile
0.141
CO₂ from the fuel
87.1 kg
검증 출처: Python decimal: 312/9.8 = 31.8367 mpg; ×4.54609/3.785411784 = 38.2343 UK mpg; 100×9.8×3.785411784/(312×1.609344) = 7.3882 L/100 km; 9.8×8.887 kg = 87.09 kg (EPA factor)
fueleconomy.gov worked example
Calculate from
One fill-up
Distance in
마일
Fuel in
미국 갤런
Distance from
Odometer readings
Odometer at last fill-up
32,645.1
Odometer now
33,001.3
Fuel added to refill the tank
13.5
Fuel price per gallon or liter
4.48
Fuel economy (US)
26.4 mpg
Distance
356.2 mi
검증 출처: fueleconomy.gov, Calculate your own gas mileage: 33,001.3 − 32,645.1 = 356.2 miles; 356.2 ÷ 13.5 = 26.4 mpg
검증 출처: Python decimal: 410/(42/4.54609) = 44.3785 UK mpg; 410/(42/3.785411784) = 36.9528 US mpg; 4200/(410×1.609344) = 6.3653
자주 묻는 질문
How do you calculate gas mileage?
Fill the tank and note the odometer. At the next fill-up, subtract the old reading from the new one and divide by the gallons it took to fill the tank again. Driving 312 miles and adding 9.8 gallons gives 312 ÷ 9.8 = 31.8 mpg. The US Department of Energy's fueleconomy.gov uses the same full-tank method in its worked example: 356.2 miles on 13.5 gallons is 26.4 mpg.
How do you convert mpg to L/100 km?
Divide 235.215 by US mpg, or 282.481 by UK mpg. The constants come from 100 × 3.785411784 L ÷ 1.609344 km for the US gallon and 100 × 4.54609 ÷ 1.609344 for the imperial gallon. So 31.8 US mpg is 7.4 L/100 km, and 7.4 L/100 km is 38.2 UK mpg. Because the relationship is a division, halving L/100 km doubles mpg.
Why should I average mpg over several fill-ups?
Pumps shut off at slightly different levels, so fuel left out of one fill-up is added at the next, making one tank read high and the next low. fueleconomy.gov warns that an estimate is not accurate unless the tank is filled completely. Dividing the total miles of all fill-ups by their total gallons cancels most of that error. Averaging the per-tank mpg figures instead gives short tanks the same weight as long ones and overstates economy when the tanks vary.
How much CO₂ does a gallon of gas produce?
Burning one gallon of gasoline produces about 8,887 grams of CO₂, and a gallon of diesel about 10,180 grams, according to the US Environmental Protection Agency. A car averaging 31.8 mpg therefore emits about 280 grams of CO₂ per mile from its tailpipe. EPA's typical passenger vehicle, at 22.2 mpg and 11,500 miles a year, emits about 4.6 metric tons a year. The figure scales with fuel burned, so each mpg gained lowers emissions in proportion.
What is the cost per mile of driving?
Fuel cost per mile is the price per gallon divided by mpg: $4.48 ÷ 31.8 mpg is 14.1 cents a mile. That covers fuel only. The IRS business standard mileage rate, 76 cents a mile from 1 July 2026 (IR-2026-29), also covers depreciation, insurance, repairs and tires, so it is more than five times the fuel cost of this car.
“Gas mileage calculator (MPG calculator)”의 정확도는 어느 정도인가요?
정확도는 입력값과 계산 방법의 가정에 따라 달라집니다. 십진 연산은 유효숫자 50자리를 사용하지만, 추정값·수치해석 방법·원본 데이터의 정밀도는 더 낮을 수 있습니다. 표시값을 반올림해도 이러한 한계는 사라지지 않습니다. 독립적인 출처의 풀이와 대조한 계산 예시: 6. 예를 들어 “312 miles on 9.8 US gallons at $4.48”은 Python decimal: 312/9.8 = 31.8367 mpg; ×4.54609/3.785411784 = 38.2343 UK mpg; 100×9.8×3.785411784/(312×1.609344) = 7.3882 L/100 km; 9.8×8.887 kg = 87.09 kg (EPA factor)와 대조해 확인합니다.
이 계산 방법의 출처는 무엇인가요?
US DOE / EPA fueleconomy.gov — Calculate your own gas mileage (My MPG); NIST SP 811 Appendix B.9 — gallon (US and imperial) and mile conversion factors; US EPA — Greenhouse gas emissions from a typical passenger vehicle (8,887 g CO₂ per gallon of gasoline).