Free IFTA Calculator: Calculate Your Fuel Tax in Seconds
Use our free IFTA calculator to estimate your quarterly fuel tax liability. Enter your miles and fuel purchases by state, and instantly see what you owe or what credits you're due.
Free IFTA Tax Calculator
Leave blank to use 6.0 MPG default
Enter miles and fuel for each state:
How to Use This IFTA Calculator
- Enter your Fleet MPG - Your average miles per gallon across all vehicles. If unsure, use 6.0 MPG as a starting estimate for diesel trucks.
- Add each state - For every state you drove in during the quarter, enter the total miles driven and gallons of fuel purchased in that state.
- Click Calculate - The calculator will show taxable gallons, net gallons, and tax due/credit for each state.
Understanding Your Results
Taxable Gallons
The amount of fuel consumed in a state, calculated by dividing miles driven by your fleet MPG.
Net Gallons
Taxable gallons minus fuel purchased. Positive means you owe tax; negative means you have a credit.
Tax Due (Positive = Red)
You consumed more fuel in this state than you purchased there. You owe tax on the difference.
Tax Credit (Negative = Green)
You purchased more fuel in this state than you consumed. You get credit for the excess tax paid.
Why Tax Rates Vary By State
IFTA diesel tax rates range from $0.18/gallon (Mississippi) to over $1.09/gallon (California). This huge variation is why strategic fueling matters - buying fuel in low-tax states before driving through high-tax states can save thousands annually.
| Lowest Tax States | Rate | Highest Tax States | Rate |
|---|---|---|---|
| Mississippi | $0.18 | California | $1.09 |
| Oklahoma | $0.19 | Pennsylvania | $0.74 |
| Texas | $0.20 | Illinois | $0.74 |
| Louisiana | $0.20 | Indiana | $0.61 |
Limitations of Manual Calculation
While this calculator gives you a quick estimate, manual IFTA calculation has significant challenges:
- Data collection is tedious - Recording miles at every state line and saving every fuel receipt takes time
- Tax rates change quarterly - You need to verify current rates before each filing
- Errors are common - Manual data entry leads to mistakes that cause audit issues
- No optimization - Manual tracking doesn't help you make smarter fueling decisions
Automate Your IFTA with FleetCollect
FleetCollect eliminates manual IFTA tracking entirely. Our mobile app uses GPS to automatically track your miles by state as you drive - no odometer readings, no spreadsheets, no guesswork.
What FleetCollect Automates
- State mileage tracking - GPS logs every mile in every state automatically
- Fuel purchase logging - Snap receipt photos with location auto-detected
- Real-time calculations - See your IFTA position as you drive
- Quarterly reports - Generate filing-ready reports in minutes
- Tax optimization tips - Know where to fuel up to maximize credits
Skip the Spreadsheets
Let FleetCollect handle your IFTA tracking automatically. Start your free 7-day trial today.
Frequently Asked Questions
How accurate is this calculator?
This calculator uses Q4 2025 IFTA tax rates and provides estimates. For official filings, always verify current rates at the official IFTA tax matrix.
What MPG should I use?
Use your actual fleet average. If unsure, 6.0 MPG is a reasonable starting point for diesel trucks. More fuel-efficient trucks might average 7-8 MPG, while older vehicles may be closer to 5 MPG.
Why do I owe tax to states where I bought fuel?
If you drove more miles in a state than the fuel you bought there would cover, you still owe tax on those "unfueled" miles. IFTA ensures states are compensated for road use regardless of where you purchased fuel.
How do I file my actual IFTA return?
IFTA returns are filed with your base jurisdiction (the state where your vehicles are registered). Most states offer online filing through their motor carrier services portal. See our complete guide to filing IFTA for step-by-step instructions.
More IFTA Resources
How to File IFTA Step-by-Step | IFTA Tax Credits Optimization | Best IFTA Software Compared | 2025 Compliance Deadlines
Disclaimer: This calculator is for estimation purposes only. Tax rates are subject to quarterly changes. Always verify current rates with the official IFTA tax matrix before filing. Consult a tax professional for complex situations.