Know before
you go.

Calculate fuel & cost before you pull up to the pump.

Real-time prices
Works offline

Fill up in the morning — fuel is denser when it's cool, so you get slightly more per gallon.

Free · No app store · Works offline

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.

Live local prices🚗Rental car mode📊MPG tracking🤖AI advisor

How to use

1Pick a vehicle
2Set fuel level

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.

3Choose a goal

Fill Up To

4Get the answer

Gas Price per Gallon

$
💾

Save your calculations

Free account — no credit card ever.

Sign up free

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

Free — no credit card ever

Know before
you pull up.

Save your vehicles, track your MPG, and stop over-paying at the pump.

Create free account →

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