MPG Calculator
Track your vehicle's real-world fuel economy after each fill-up to monitor driving habits, maintenance, and fuel costs.
How to Use This Calculator
Record your starting odometer
Reset your trip meter or note the reading before you begin driving.
Refill and note gallons used
At your next fill-up, record the odometer and fuel pumped to determine consumption.
Enter fuel price (optional)
Include the price per gallon to calculate cost per mile and trip total.
Review MPG and efficiency metrics
Track results over time to identify maintenance issues or changes in driving habits.
Formula
MPG = (Odometer End − Odometer Start) ÷ Gallons Used
Liters per 100 km: (100 × 3.78541) ÷ (MPG × 1.60934)
Example: Start 15,230 mi, end 15,680 mi, 16.5 gal used, $3.85/gal:
Distance = 450 miles → MPG = 450 ÷ 16.5 = 27.27 mpg
Fuel cost = 16.5 × 3.85 = $63.53 → Cost per mile = $63.53 ÷ 450 = $0.14
L/100 km = (100 × 3.78541) ÷ (27.27 × 1.60934) = 8.63 L/100 km
About the MPG Calculator
Manufacturer MPG ratings rarely match real-world driving. Use this calculator to measure actual efficiency after maintenance, seasonal changes, or modifications.
When to Use This Calculator
- Monitoring performance: Track MPG after tune-ups, tire changes, or engine mods.
- Budgeting fuel costs: Use your true MPG for accurate trip and monthly budgeting.
- Driver coaching: Encourage fuel-efficient habits by comparing MPG between fills.
- Fleet management: Identify poorly performing vehicles or maintenance needs.
Why Use Our Calculator?
- ✅ Metric conversion: View results in MPG and liters per 100 km.
- ✅ Cost insights: Optional fuel price input reveals cost per mile or kilometer.
- ✅ Quick workflow: Just four inputs—ideal for keeping a fill-up log.
- ✅ Mobile ready: Use at the gas pump to log trips immediately.
Common Applications
Commuters: Track MPG across seasons to adjust fuel budgets.
Delivery drivers: Monitor efficiency losses due to idling or stop-and-go routes.
Car enthusiasts: Compare MPG before and after performance upgrades.
Tips for Best Results
- Fill up to the same pump shut-off level to keep measurements consistent.
- Record at least three fill-ups to smooth out short-term variability.
- Consider temperature, tire pressure, and driving style when interpreting MPG changes.
- Reset your trip meter at each fill-up for faster calculations.
Frequently Asked Questions
Can I enter trip distance directly?
If you already know the distance, set the starting odometer to zero and ending to the trip distance. The difference will equal your miles driven.
How often should I calculate MPG?
Many drivers log MPG at every fill-up and track trends over time. Frequent calculations help catch drops in efficiency early.
Does idling affect MPG?
Yes. Idling consumes fuel without adding miles, lowering MPG. Expect lower fuel economy if your vehicle idles frequently.
What about diesel or alternative fuels?
The MPG calculation works the same for any liquid fuel. Just make sure to enter the correct fuel price if you want cost-per-mile results.