Know exactly how much gas you need — before you pull up.
GasCap calculates your exact fill-up cost using live local gas prices. No more guessing, no more overpaying — especially on rental car returns.
How to use
Current Fuel Level
Drag the handle · or tap anywhere on the arc
Sign in to use AI gauge scan and auto-detect your fuel level from a photo.
Fill Up To
Gas Price per Gallon
Tools & Insights
Stop guessing at the pump
GasCap solves the three most frustrating gas station moments.
Wondering if you have enough cash to fill up
✓ Know the exact cost before you swipe your card
Returning a rental car on empty — $12/gallon fees
✓ Calculate exactly how many gallons to buy first
No idea what you're spending on gas each month
✓ MPG trends and monthly spend tracked automatically
Everything in one free app
Live gas prices
Real-time local prices from the U.S. EIA — automatically localized to your state.
Works offline
Install it like an app. No signal? The calculator always works with your saved data.
MPG & spend tracking
Log every fill-up. See your efficiency trends, monthly spend, and fuel cost per mile.
AI fuel advisor
Ask anything — best fill strategy, octane grade, or how to improve your MPG.
Renting a car? Never overpay at drop-off.
Rental companies charge up to $12/gal if you return empty. GasCap™ Rental Car Return Mode tells you exactly how many gallons to buy — and shows your exact savings vs. letting them fill it.
Toggle "🚗 Rental Car Return?" in the calculator above.
Who uses GasCap™
Daily Drivers
Know your fill-up cost every time. Budget your gas spend to the dollar.
Frequent Travelers
Use Rental Car Return Mode to skip the $12/gal refueling trap every trip.
Road Trippers
Plan your fuel budget stop by stop. Know costs before you leave the driveway.
Fleet Managers
Track fuel costs across your entire fleet. Export reports. Control spending.
Free
Forever — no catch
5.0★
Average rating
<2s
Typical calculation
Frequently Asked Questions
Know before
you pull up.
Save your vehicles, track your MPG, and stop over-paying at the pump.
Create free account →Already have an account? Sign in