MPG Calculator (Miles Per Gallon & Fuel Cost)

Calculate your vehicle's real-world miles per gallon (MPG) from your odometer or trip meter, convert US vs UK Imperial gallons, and compute fill-up costs instantly.

Live Tank-Fill MPG Calculator

Calculate exact miles per gallon from your odometer or trip meter.

mi

Distance from your trip odometer

gal

Gallons from your gas pump receipt

$/gal

Local price per gallon

Calculated Fuel Economy
33.3Miles Per Gallon (US MPG)
Excellent Efficiency (Sedan / Crossover)
UK Imperial MPG40.0 MPG UK
Metric Equivalent7.06 L/100km
Cost Per Mile$0.10 / mi
Fill-Up Total Cost$36.23
Featured Snippet Reference

Official Miles Per Gallon (MPG) Formula

The universal mathematical formula used by automotive manufacturers and regulatory agencies to measure liquid fuel economy.

Miles Per Gallon (MPG) = Total Miles Driven ÷ Total Gallons Used
Tank-Fill Example360 miles ÷ 12 gallons30.0 MPG
UK Imperial Conversion30.0 US MPG × 1.2009536.03 UK MPG
Cost Per Mile$3.45/gal ÷ 30.0 MPG$0.115 / mile

Standard Distance Fuel & Cost Benchmark Matrix

Estimated fuel volume and trip costs across typical vehicle efficiency tiers (calculated at $3.50/gal gasoline and $0.19/kWh electricity).

Trip Distance20 MPG (Truck/SUV)30 MPG (Sedan)50 MPG (Hybrid)EV (120 MPGe)
25 miles (Daily commute)1.25 gal ($4.38)0.83 gal ($2.92)0.50 gal ($1.75)7.0 kWh ($1.33)
50 miles (Round-trip work)2.50 gal ($8.75)1.67 gal ($5.83)1.00 gal ($3.50)14.0 kWh ($2.66)
100 miles (Regional trip)5.00 gal ($17.50)3.33 gal ($11.67)2.00 gal ($7.00)28.0 kWh ($5.32)
250 miles (Weekend getaway)12.50 gal ($43.75)8.33 gal ($29.17)5.00 gal ($17.50)70.0 kWh ($13.30)
500 miles (Interstate route)25.00 gal ($87.50)16.67 gal ($58.33)10.00 gal ($35.00)140.0 kWh ($26.60)

Benchmark calculations use standard national averages. You can customize exact distances, gas prices, and vehicle MPG in the live calculator above.

How Miles Per Gallon (MPG) Is Calculated

Miles Per Gallon (MPG) is the primary unit of fuel economy measurement used in the United States, the United Kingdom, and several island nations. It measures distance traveled per unit volume of fuel consumed. Higher MPG values reflect superior fuel efficiency, meaning the vehicle travels further on a single gallon of gas or diesel.

Calculating your vehicle's true MPG is essential for budgeting travel costs, monitoring engine health, and determining when maintenance is required. A sudden drop in MPG often indicates low tire pressure, a clogged air filter, failing oxygen sensors, or dragging brake calipers.

The Step-by-Step Tank-Fill Method

Digital dashboard displays often overestimate mileage by 5% to 15%. To measure your true MPG with zero error:

  1. Fill Up Completely: Visit a gas station and fill your tank until the pump nozzle automatically clicks off. Record your exact odometer mileage (e.g., 45,200 miles).
  2. Drive Normally: Drive your routine routes until your fuel gauge reaches a quarter tank or less.
  3. Refill and Record: Return to the pump, fill up completely again, and note the exact gallons pumped (e.g., 12.4 gallons) and your new odometer reading (e.g., 45,572 miles).
  4. Calculate Distance: Subtract initial mileage from final mileage: 45,572 - 45,200 = 372 miles.
  5. Compute MPG: Divide total miles by total gallons: 372 miles ÷ 12.4 gallons = 30.0 MPG.

Real-World MPG Calculation Examples

Example 1: Daily Commuter Sedan (Honda Civic / Toyota Corolla)

A driver travels 420 miles on a full 11.5-gallon tank refill of regular gasoline priced at $3.40 per gallon.

  • Calculation: 420 miles ÷ 11.5 gallons = 36.52 MPG US.
  • UK Imperial MPG: 36.52 × 1.20095 = 43.86 MPG UK.
  • Metric Equivalent: 235.215 ÷ 36.52 = 6.44 L/100km.
  • Fill Cost: 11.5 gal × $3.40 = $39.10 total.
  • Cost Per Mile: $3.40 ÷ 36.52 MPG = $0.093 / mile.

Example 2: Full-Size Pickup Truck (Ford F-150 / Chevy Silverado)

A truck owner drives 460 miles across combined city towing and highway hauling, refilling 24.0 gallons of gas at $3.75 per gallon.

  • Calculation: 460 miles ÷ 24.0 gallons = 19.17 MPG US.
  • UK Imperial MPG: 19.17 × 1.20095 = 23.02 MPG UK.
  • Metric Equivalent: 235.215 ÷ 19.17 = 12.27 L/100km.
  • Fill Cost: 24.0 gal × $3.75 = $90.00 total.
  • Cost Per Mile: $3.75 ÷ 19.17 MPG = $0.196 / mile.

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Frequently asked questions

Fill your gas tank completely at a gas station until the pump nozzle shuts off automatically, then record your exact odometer reading. Drive normally until your tank is below 1/4 full, then fill up completely again at the same pump if possible. Record the gallons filled and your new odometer reading. Subtract your starting odometer reading from the ending odometer reading to find total miles driven, then divide miles driven by gallons filled (Miles ÷ Gallons = MPG).

A US liquid gallon is 3.78541 liters, whereas an Imperial (UK) gallon is 4.54609 liters (approx 20% larger). Because a UK gallon holds more fuel, a car tested in the UK will yield a 20% higher MPG figure than the exact same car tested in the US. For instance, a vehicle rated at 30 US MPG is equal to 36.03 UK MPG.

For gasoline sedans, 30+ MPG combined is considered good. Compact hybrid cars typically achieve 45 to 55 MPG. Midsize SUVs average 22 to 28 MPG, while full-size pickup trucks average 16 to 22 MPG.

Aerodynamic drag increases exponentially with speed. Driving at 75 mph consumes roughly 20% more fuel than driving at 55 mph. Every 5 mph you drive over 50 mph is equivalent to paying an extra $0.25 to $0.30 per gallon of gas.

EPA tests are conducted in lab settings under controlled indoor temperatures on dynamometers. Real-world factors such as rapid acceleration, roof rack drag, under-inflated tires, heavy passenger loads, cold weather, and extensive engine idling reduce actual MPG by 10% to 25%.

To convert US MPG to L/100km, divide 235.215 by your US MPG figure. To convert UK MPG to L/100km, divide 282.481 by your UK MPG figure.

Yes. Operating the air conditioner in hot weather can reduce fuel economy by 5% to 20%, especially during short trips in city traffic. At highway speeds above 45 mph, using AC is generally more efficient than opening windows due to aerodynamic drag.

Tires naturally lose about 1 PSI per month. Tires that are 5 to 7 PSI below the vehicle manufacturer's recommended level on the driver's door jamb can reduce fuel economy by 2% to 3% and accelerate tire tread wear.