Gas Calculator
Figure out the gallons required to top off your tank, the estimated cost, and your driving range based on your vehicle's fuel economy.
How to Use This Calculator
Enter your tank capacity
Check the owner's manual or search online for your vehicle's fuel tank size.
Update your current fuel level
Use the gauge reading or onboard computer to estimate the percentage remaining.
Add fuel price and MPG
Enter today's pump price and your vehicle's average fuel economy (mpg).
Review fill-up cost and range
See how many gallons you need, how much it will cost, and how far your fuel will take you.
Formula
Gallons Needed = Tank Capacity × (1 − Fuel Level ÷ 100)
Cost to Fill: Gallons Needed × Fuel Price
Range Miles: Gallons × MPG
Example with 15 gallon tank, 40% remaining, $3.89/gal, 28 mpg:
Current fuel = 15 × 0.40 = 6.0 gal
Gallons to fill = 15 − 6 = 9 gal → Cost = 9 × 3.89 = $35.01
Current range = 6 × 28 = 168 miles; Full tank range = 15 × 28 = 420 miles
About the Gas Calculator
Gas prices fluctuate constantly, making it hard to budget fill-ups or long drives. This calculator summarizes the essentials: how many gallons you have, how many you need, and how far you can go before the next stop.
When to Use This Calculator
- Trip preparation: Decide whether to fill up before hitting the road.
- Budgeting fuel costs: Estimate weekly or monthly gasoline spending.
- Vehicle comparisons: Compare the range and cost of different cars.
- Fleet management: Track fuel needs across multiple vehicles.
Why Use Our Calculator?
- ✅ Instant range estimates: Know how many miles you can travel right now.
- ✅ Cost transparency: Plan fill-ups so fuel expenses don't surprise you.
- ✅ Mobile friendly: Use at the gas station or on the go.
- ✅ Free and flexible: Adjust fuel economy, tank size, and price anytime.
Common Applications
Families: Plan vacation stops and avoid running low on unfamiliar routes.
Commuters: Estimate weekly fill-up costs based on current prices.
Student drivers: Understand how fuel level, MPG, and price interact.
Tips for Best Results
- Recalculate when fuel prices change significantly.
- Use real-world MPG data; highway and city driving differ.
- Remember that aggressive driving lowers fuel economy.
- Keep at least a small reserve—don't plan on using 100% of your tank.
Frequently Asked Questions
How accurate is the fuel level percentage?
The gauge on many vehicles is approximate. For more precision, track gallons added at the pump or use vehicles with digital fuel level readouts.
Can I use liters and kilometers?
Enter tank size in gallons and MPG for now. The results section shows liters and cost per kilometer. Future updates may include native metric inputs.
What if I don't know my MPG?
Use your vehicle's rated MPG or calculate it by dividing miles driven by gallons refilled over multiple tanks.
Why does the calculator show cost per mile?
Cost per mile helps compare different vehicles or fuel prices. It shows what you spend in fuel to travel a single mile based on your inputs.