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everydayAutomotive

Gas Mileage Calculator

Determine your vehicle actual real-world fuel economy in MPG and L/100 km by tracking odometer trip distance and fuel pumped.

Gas Mileage & Fuel Economy Calculator

Calculate your vehicle's real-world MPG and L/100 km fuel consumption from odometer readings.

miles

Trip odometer mileage since last full fill-up.

gallons

Exact volume pumped on the receipt to refill the tank.

Fuel Efficiency
27.83 MPG

Equivalent to 8.45 L/100 km

US Fuel Economy27.83 MPGMiles per gallon
Metric Consumption8.45 L/100kmLiters per 100 kilometers
Distance Logged320 milesBetween fill-ups
Fuel Added11.5 gallonsPumped to full tank
Calculation Steps
  • 1.Calculate Miles Per Gallon: 320.0 miles ÷ 11.50 gallons = 27.83 MPG
  • 2.Convert to metric consumption: 235.215 ÷ 27.83 MPG = 8.45 L/100 km

Mathematical Formula & Calculation Method

MPG = Distance (miles) / Gallons Pumped | L/100km = (Liters / Kilometers) × 100

Formula Components:

  • Miles Per Gallon (US) = Trip Distance (miles) ÷ Gallons Used
  • Metric Consumption = (Fuel Used in Liters ÷ Distance in km) × 100
  • Conversion Factor: MPG × L/100km = 235.215

How It Works

1

Select US (miles/gallons) or Metric (km/liters).

2

Enter the miles driven recorded on your trip odometer since your last fill-up.

3

Enter the exact volume of fuel pumped to refill the tank full.

4

The calculator computes your MPG and dual metric equivalent.

Practical Calculation Examples

320 Miles on 11.5 Gallons

Commuter car filled to the click after a week of mixed driving.

Step 1:Divide miles by gallons: 320 ÷ 11.5 = 27.83 MPG.
Step 2:Convert to metric: 235.215 ÷ 27.83 = 8.45 L/100 km.
Outcome: Vehicle achieved 27.83 MPG (8.45 L/100 km).

Important Assumptions & Estimator Guidance

  • Fuel tank is filled to the automatic shutoff click at both start and end points of the test.
  • Tire pressure matches manufacturer door jamb specification to avoid odometer error.

Common Pitfalls & Mistakes to Avoid

Relying solely on dashboard digital estimates

In-dash fuel economy readouts frequently read 2-5% optimistic compared to actual pump measurements.

Correction: Divide odometer miles by pump gallon receipt values over 3 consecutive fill-ups for accuracy.
In-Depth Companion Guide

How to Calculate Gas Mileage

Calculate your vehicle true fuel economy in miles per gallon (MPG) using real fill-up odometer readings, and understand why dashboard gauges differ.

Read Companion Guide

Frequently Asked Questions

For non-hybrid gasoline sedans, 30+ MPG combined is considered good. Hybrid vehicles frequently achieve 45 to 55+ MPG.

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