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Mileage Calculator

Calculate fuel efficiency in MPG and L/100km, cost per mile, and estimated monthly fuel costs. Supports miles/gallons and km/liters.

What is Mileage Calculator?

A mileage calculator computes your vehicle's fuel efficiency in multiple units (MPG, L/100km, km/L) and estimates your fuel costs per mile and per month. It helps you track fuel economy, compare vehicles, and budget for transportation costs.

How to use

  1. 1 Select your unit system: miles/gallons (US) or km/liters (metric).
  2. 2 Enter the distance driven and fuel used from a full tank to full tank fillup.
  3. 3 Enter your fuel price per gallon (or per liter) for cost estimates.
  4. 4 Optionally enter your monthly mileage to get a monthly fuel cost estimate.
  5. 5 Click Calculate to see all fuel economy metrics.

Formula

MPG = Miles / Gallons. L/100km = 235.215 / MPG. km/L = MPG × 0.425144. Cost per mile = Fuel price / MPG. Monthly cost = (Monthly miles / MPG) × Fuel price.

Example calculation

Driving 300 miles on 12 gallons: MPG = 300/12 = 25. L/100km = 235.215/25 = 9.41. At $3.50/gal, cost per mile = $3.50/25 = $0.14. Driving 1,500 miles/month: monthly cost = (1500/25) × $3.50 = $210.

Frequently asked questions

How do I measure MPG accurately?

Fill your tank completely, reset your trip odometer, drive normally until you need fuel, fill up again, and record the miles driven and gallons added. This gives you one accurate MPG reading.

What is a good MPG?

For most passenger cars, 30+ MPG is good. Hybrids typically achieve 45–55 MPG. SUVs and trucks average 15–25 MPG. EVs are measured in MPGe (miles per gallon equivalent).

Why does L/100km go down when MPG goes up?

L/100km measures consumption (lower is better). MPG measures efficiency (higher is better). They are inversely related: better fuel economy = lower L/100km and higher MPG.

How much does a 1 MPG improvement save?

Going from 20 to 21 MPG saves about $50/year at 12,000 miles/year and $3.50/gallon. Improvements at lower MPG ranges save more than improvements at higher ranges.

Does speed affect fuel economy?

Yes. Fuel economy peaks around 45–55 mph for most vehicles. Above 60 mph, aerodynamic drag increases significantly and MPG drops. Every 5 mph above 60 costs roughly 7–14% in fuel economy.