IFTA Calculator

How IFTA Is Calculated, Step by Step With an Example

Updated

An IFTA return looks long, but every line comes from two numbers per jurisdiction: miles driven and tax-paid gallons bought. Below is the order the math runs in, plus a small example you can redo with a pencil. The rates in the example are made up to keep the arithmetic clean, so use the current IFTA matrix for real numbers.

The five steps

Add up total miles in every jurisdiction, including non-IFTA places like Alaska, and total gallons put in the truck. Divide miles by gallons to get fleet MPG for the quarter. For each jurisdiction, divide its taxable miles by that MPG to get taxable gallons, the fuel the truck burned there. Subtract the tax-paid gallons you bought there to get net taxable gallons, then multiply by the jurisdiction's rate. A positive result is tax due, a negative one is a credit, and the sum of all lines is what you pay or get back.

A worked example

Say a truck ran 6,000 miles in State A and 4,000 miles in State B, and bought 1,000 gallons in A and 600 in B. Total miles are 10,000 and total gallons 1,600, so fleet MPG is 6.25. Taxable gallons come out to 960 in A and 640 in B. State A shows 40 gallons more bought than burned, a credit; State B shows 40 gallons burned but not bought, tax due. At made-up rates of $0.30 in A and $0.50 in B, that is a $12.00 credit and $20.00 due, so the return nets to $8.00 owed.

Surcharges, split rates and rounding

A surcharge line is charged on all taxable gallons in its jurisdiction, and fuel bought there does not offset it, so it always shows tax due if you drove there. When a state changes its rate partway through a quarter, the matrix lists both rates and you report the miles for each period separately. Base jurisdictions set their own rounding rules for MPG and gallons, so expect totals to differ by a few cents from a hand calculation. Late returns add interest and penalties, which this calculator does not compute.

Quarterly due dates

A return covers one calendar quarter and is due at the end of the following month, together with the payment. When that day falls on a weekend, the date moves to the next business day. For 2026 that gives April 30 for the first quarter, July 31 for the second, November 2 for the third, and February 1, 2027 for the fourth. You file every quarter even if you owe nothing, and a credit carries forward or is refunded by your base jurisdiction.

Where the rates in this calculator come from

IFTA, Inc. publishes the rate matrix before each quarter starts, and member jurisdictions reprint it. The calculator takes the U.S. dollars per gallon column for diesel, gasoline, propane, LNG and CNG, and checks each quarter against at least two state copies before it goes on the site: Pennsylvania's IFTA-400 and Colorado's quarterly table, plus New York's IFTA-105 where those two disagree. The quarter and the check date sit above your rows. A rate a state changes after the matrix comes out may not be in it yet, which is one more reason to treat the result as an estimate.

What IFTA does not cover

Some states charge separate road taxes filed outside IFTA: Oregon's weight-mile tax, New York's highway use tax, Kentucky's KYU and New Mexico's weight-distance tax. Electricity and hydrogen, which a few states tax per mile, are also outside this calculator, as are Canadian kilometres and litres for carriers based in Canada.

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