The IFTA fuel tax is a quarterly filing that reconciles fuel taxes across all states you drove through. When you buy more fuel in a state than you used there, you get a credit. When you used more than you bought, you owe tax. This calculator computes net tax owed or refunded for each state using 2026 IFTA rates.
Miles by State
| State | Miles Driven | Gallons Purchased |
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How to Use the IFTA Fuel Tax Calculator
IFTA quarterly filing requires tracking miles driven and fuel purchased in each state. This calculator does the math — fleet average MPG, taxable gallons per state, and net tax owed or refunded per state.
Step 1: Enter Quarter Totals
Select your filing quarter, then enter total fleet miles driven for the quarter and total gallons of diesel purchased across all states. The calculator uses these to compute your fleet's average fuel economy, which is central to IFTA math.
Step 2: Enter Miles by State
Add a row for each state you drove through. Enter the miles driven in that state and how many gallons you purchased there. If you didn't buy fuel in a state, enter 0 gallons purchased.
Step 3: How IFTA Tax Is Calculated
The calculation: First, average MPG = total miles ÷ total gallons. For each state: taxable gallons = state miles ÷ average MPG. Net tax = (taxable gallons × state rate) - (gallons purchased in state × state rate). A negative net tax means that state owes you a refund.
Understanding Results
States where you drove many miles but bought little fuel will show tax owed. States where you fueled up heavily (like at low-tax stops) will show credits or refunds. The net total across all states is what you pay or receive for the quarter.
Filing Tips
Keep all fuel receipts organized by state. Electronic logging devices (ELDs) often track state mileage automatically. File on time — late IFTA penalties are $50 or 10% of tax owed. Some base jurisdictions offer IFTA online filing portals.
FAQ
Is this IFTA fuel tax calculator free?
Yes, completely free with no signup required. All calculations run in your browser. No data is transmitted to any server. Always verify IFTA rates with your base jurisdiction before filing.
What is IFTA and who needs to file?
IFTA (International Fuel Tax Agreement) is an agreement between US states and Canadian provinces that simplifies fuel tax reporting for interstate commercial motor vehicles. You must file IFTA quarterly if you operate a vehicle with 3+ axles, or 2 axles and a GVWR over 26,000 lbs, that travels in 2+ IFTA jurisdictions.
How is IFTA tax calculated?
IFTA calculates net tax owed per state using your fleet's average fuel efficiency. The formula: (1) Calculate average MPG = total miles / total gallons. (2) For each state: taxable gallons = state miles / average MPG. (3) Net tax = (taxable gallons × state rate) - (gallons purchased in state × state rate). States where you bought more fuel than you used may owe you a refund.
When is IFTA due?
IFTA returns are due quarterly: Q1 (Jan-Mar) due April 30, Q2 (Apr-Jun) due July 31, Q3 (Jul-Sep) due October 31, Q4 (Oct-Dec) due January 31. Late filing penalties are $50 or 10% of tax owed, whichever is greater.
Which states are included in IFTA?
All 48 contiguous US states plus the District of Columbia and 10 Canadian provinces. Alaska, Hawaii, and the territories are not part of IFTA. This calculator covers the 48 lower states + DC.
Does this calculator support metric units?
Yes. Toggle the unit switch to enter data in km and liters instead of miles and gallons. The calculator converts all values internally for accurate IFTA calculation.
How often do IFTA tax rates change?
IFTA fuel tax rates change quarterly in some states and annually in others. The rates in this calculator are updated annually. Always verify current rates at your base jurisdiction's IFTA office before filing your quarterly return.