To calculate MPG (miles per gallon), divide the miles driven by the gallons of gas used. If you drove 300 miles and used 10 gallons, your car gets 30 MPG. Track this over multiple fill-ups for an accurate picture of your true fuel economy.

I have been tracking MPG on my 2020 Accord for over 18 months and 22,000 miles now. My EPA-rated 33 MPG combined actually averages 29.4 MPG in real-world driving — 11% below the sticker. Once I started checking tire pressure weekly and easing off the gas pedal, I brought it up to 31.2 MPG, saving roughly $180 a year at current gas prices.

Use our Gas Mileage Calculator to instantly calculate your MPG and compare it to EPA estimates.

How to Calculate Miles Per Gallon

The Basic Formula

MPG = Miles Driven ÷ Gallons Used

Step-by-Step Calculation

Step 1: Fill your tank completely and record the odometer reading

Step 2: Drive normally until you need to refuel

Step 3: Fill the tank again and record:

New odometer reading
Gallons added to fill the tank

Step 4: Calculate:

Miles Driven = New Odometer - Previous Odometer
MPG = Miles Driven ÷ Gallons Added

Example Calculation

Previous odometer: 45,230 miles
New odometer: 45,580 miles
Gallons to fill: 12.5 gallons

Miles driven: 45,580 - 45,230 = 350 miles
MPG: 350 ÷ 12.5 = 28 MPG

Tip

Track over multiple fill-ups. A single tank can be affected by driving conditions, weather, and routes. Average 3-5 fill-ups for your true MPG.

Understanding Fuel Economy Ratings

EPA Fuel Economy Numbers

The EPA provides three ratings for every vehicle:

Rating	What It Means
City MPG	Stop-and-go driving, speeds under 45 mph
Highway MPG	Steady speeds, typically 45-65 mph
Combined MPG	55% city + 45% highway weighted average

Why Real-World MPG Differs from EPA

Factor	Effect on MPG
Aggressive driving	-15% to -30%
Cold weather	-10% to -20%
Short trips	-10% to -25%
Excess weight	-1% to -2% per 100 lbs
Roof cargo	-5% to -25%
A/C use	-5% to -10%
Under-inflated tires	-1% to -3%

Info

Most drivers get 10-15% less than EPA ratings. This is normal. EPA testing uses controlled conditions that don't reflect typical driving.

MPG vs. L/100km: Converting Units

Different countries use different fuel economy measures:

Conversion Formulas

MPG to L/100km:

L/100km = 235.215 ÷ MPG

L/100km to MPG:

MPG = 235.215 ÷ L/100km

Quick Reference Table

MPG (US)	L/100km	Description
15	15.7	Large truck/SUV
20	11.8	Older sedan, small SUV
25	9.4	Average car
30	7.8	Efficient sedan
35	6.7	Very efficient
40	5.9	Hybrid territory
50	4.7	Efficient hybrid
60+	<4.0	Plug-in hybrid (gas only)

US vs. Imperial Gallons

Important: US and UK gallons are different:

US gallon = 3.785 liters
Imperial gallon = 4.546 liters

UK MPG is about 20% higher than US MPG for the same fuel consumption.

What's Good Gas Mileage?

By Vehicle Type (2026 Standards)

Vehicle Type	Poor	Average	Good	Excellent
Compact car	<28	28-35	35-45	45+
Midsize sedan	<25	25-32	32-40	40+
Full-size sedan	<22	22-28	28-35	35+
Small SUV/Crossover	<24	24-30	30-38	38+
Large SUV	<18	18-23	23-28	28+
Pickup truck	<16	16-22	22-26	26+
Sports car	<20	20-26	26-32	32+
Hybrid	<40	40-50	50-55	55+
Plug-in hybrid	<35	35-50	50-90	90+

If you are considering switching to electric, our EV vs gas cost comparison guide breaks down how fuel economy translates into long-term savings.

Fuel Economy Trends

Average new vehicle fuel economy (US):

1975: 13.5 MPG
1990: 20.2 MPG
2000: 20.1 MPG
2010: 23.5 MPG
2020: 25.7 MPG
2026: ~28 MPG (projected)

Calculating Fuel Costs

Cost Per Mile

Cost per Mile = Gas Price ÷ MPG

Example (30 MPG at $3.50/gallon):

$3.50 ÷ 30 = $0.117 per mile

Annual Fuel Cost

Annual Cost = (Annual Miles ÷ MPG) × Gas Price

Example (12,000 miles, 28 MPG, $3.50/gallon):

(12,000 ÷ 28) × $3.50 = 428.6 × $3.50 = $1,500/year

Cost Comparison Between Vehicles

MPG	12,000 mi @ $3.50/gal	15,000 mi @ $3.50/gal
20	$2,100	$2,625
25	$1,680	$2,100
30	$1,400	$1,750
35	$1,200	$1,500
40	$1,050	$1,313
50	$840	$1,050

For trip-specific calculations, see our Road Trip Cost Calculator or read our road trip cost planning guide.

Factors That Affect Gas Mileage

Driving Habits

Habit	MPG Impact
Aggressive acceleration	-10% to -33%
Speeding (65+ mph)	-7% per 5 mph over 50
Excessive idling	-0.5 to 1 gal/hour wasted
Cruise control on highway	+5% to +10%
Anticipating stops	+5% to +15%

Vehicle Maintenance

Issue	MPG Impact
Under-inflated tires	-0.2% per 1 psi below optimal
Dirty air filter	-1% to -10%
Wrong motor oil grade	-1% to -2%
Worn spark plugs	-2% to -4%
Misaligned wheels	-2% to -10%
Dragging brakes	-5% to -10%

Environmental Factors

Factor	MPG Impact
Cold weather (20°F)	-10% to -20%
Hot weather with A/C	-5% to -10%
Hilly terrain	-5% to -20%
Headwinds	-5% to -10%
Rain/wet roads	-5%

Tip

The first few miles matter most. Your engine is least efficient when cold. Combine short trips when possible to maximize economy.

How to Improve Your Gas Mileage

Immediate Improvements

Check tire pressure weekly
- Underinflated tires increase rolling resistance
- Check when tires are cold
- Use the door jamb sticker pressure, not tire sidewall
Remove excess weight
- 100 extra pounds = 1-2% MPG loss
- Clear trunk of unnecessary items
Remove roof racks when not in use
- Roof cargo boxes reduce MPG by 6-17% at highway speeds
- Even empty racks create drag
Use cruise control on highways
- Maintains steady speed
- Prevents unconscious speeding

Driving Technique Changes

Technique	Expected Improvement
Gradual acceleration	5-10%
Coast to red lights	5-10%
Reduce max speed by 5 mph	5-7%
Avoid jackrabbit starts	10-20%
Turn off engine if idling >60 sec	Varies

Maintenance Priorities

Replace air filter (when dirty): +1-10%
Use correct oil viscosity: +1-2%
Keep engine tuned: +4%
Fix oxygen sensor if faulty: +up to 40%
Ensure proper wheel alignment: +2-10%

Tracking Your Gas Mileage

Manual Tracking Method

Create a log with these columns:

Date
Odometer reading
Gallons filled
Price per gallon
Miles since last fill
Calculated MPG

Using Apps and Technology

Method	Pros	Cons
Fuel tracking apps	Easy, calculates automatically	Requires data entry
OBD2 scanner	Real-time MPG, engine data	Upfront cost
Trip computer	Built-in, convenient	Often 5-10% optimistic
Credit card statements	Automatic record	Less detail

What Your MPG Tells You

Pattern	Possible Cause
Sudden drop	Driving conditions, maintenance issue
Gradual decline	Wear, maintenance needed
Better than usual	Good conditions, efficient driving
Inconsistent	Varied driving conditions

How to Use Our Gas Mileage Calculator

Our Gas Mileage Calculator makes tracking easy:

Enter miles driven — from odometer or trip meter
Enter gallons used — from pump receipt
Get your MPG — instant calculation

The calculator also provides:

L/100km conversion
Comparison to EPA ratings
Cost per mile at current gas prices
Estimated annual fuel cost

Frequently Asked Questions

How do I calculate miles per gallon?

Divide the miles you drove by the gallons of gas used. Example: 300 miles ÷ 12 gallons = 25 MPG. For best accuracy, fill the tank completely before and after your measurement period.

What is the average MPG for a car?

The average new car in the US gets about 28 MPG combined. Sedans typically achieve 30-40 MPG, SUVs 25-30 MPG, and trucks 18-24 MPG. Hybrids can reach 45-60 MPG.

Why is my MPG lower than the EPA rating?

EPA tests use ideal conditions that don't reflect real-world driving. Aggressive driving, cold weather, short trips, heavy cargo, and city driving all reduce MPG below EPA estimates by 10-25%.

How can I improve my gas mileage?

The biggest improvements come from: maintaining proper tire pressure (+1-3%), removing excess weight (+1-2%), driving at moderate speeds (+5-15%), accelerating gently (+5-10%), and keeping up with maintenance (+up to 10%).

Is premium gas worth it for better MPG?

Only if your car requires it. Premium won't improve MPG in vehicles designed for regular gas. If your car requires premium, using regular can reduce performance and efficiency.

How accurate is my car's MPG display?

Most dashboard MPG displays are optimistic by 5-10%. Calculate your actual MPG by dividing miles by gallons at fill-up for the most accurate reading.

Road Trip Cost Calculator — Plan fuel costs for any trip
Car Payment Calculator — Calculate monthly auto loan payments
EV vs Gas Cost Calculator — Compare electric vs gas vehicle costs

Conclusion

Knowing your true MPG helps you understand your car's efficiency, budget for fuel, and identify when something's wrong. Track your mileage over multiple fill-ups for an accurate picture, and use the improvement tips to squeeze more miles from every gallon.

Use our Gas Mileage Calculator to easily calculate your MPG and compare it to expected performance. A few simple changes in driving habits and maintenance can save you hundreds of dollars per year.

Fuel economy calculations are estimates based on standard formulas. Actual results vary based on driving conditions, vehicle maintenance, and individual driving habits.