Trucker Tools
IFTA Fuel Tax Calculator
IFTA tax is worked out per jurisdiction. Fleet MPG is total miles divided by total gallons. Taxable gallons are the miles driven in a jurisdiction divided by that MPG. Subtract the tax-paid gallons bought there, then multiply by that jurisdiction's rate. A negative line is a credit. Rates can change every quarter, so copy them from the official IFTA rate matrix.
How the IFTA math works
- Fleet MPG = total miles in all jurisdictions / total gallons used, rounded to two decimals. New Mexico's instructions give the example 19,045 miles / 3,553 gallons = 5.36 MPG.
- Taxable gallons for each jurisdiction = miles driven there / fleet MPG, in whole gallons.
- Net taxable gallons = taxable gallons - tax-paid gallons bought there. A negative number means you bought more tax-paid fuel there than you burned.
- Tax or credit = net taxable gallons x that jurisdiction's rate.
- Surcharge, where a jurisdiction has one = taxable gallons x the surcharge rate. In the IFTA rate matrix, Kentucky and Virginia have a diesel surcharge line. Indiana's surcharge line covers propane only. Tax-paid fuel does not offset a surcharge.
- Add the lines. Your base jurisdiction's return adds interest and penalties for late filing.
List every jurisdiction you drove in, so total miles and gallons cover the whole quarter. Use all fuel put in the truck, including any non-tax-paid fuel, for total gallons. Enter whole miles and whole gallons, as the return asks.
Worked example
Made-up miles and rates to show the math. Real rates can change every quarter.
- Totals: 19,000 miles / 3,553 gallons = 5.35 MPG.
- State A: 10,000 miles / 5.35 = 1,869 taxable gallons. Bought 1,000 tax-paid. Net 869 x $0.50 = $434.50 due.
- State B: 9,000 miles / 5.35 = 1,682 taxable gallons. Bought 2,553 tax-paid. Net -871 x $0.30 = -$261.30 credit, plus a $0.10 surcharge on 1,682 gallons = $168.20. Line total -$93.10.
- Return total: $434.50 - $93.10 = $341.40 due.
Before you file
- This is an estimate to check your numbers. File on your base jurisdiction's own return, with its rounding and its interest and penalty rules.
- Keep your trip records and fuel receipts. Only tax-paid gallons count as credit.
- Want to know what a mile costs before fuel tax settles up? Try the cost per mile calculator.
FAQ
How is IFTA fuel tax calculated?
Divide total miles by total gallons to get fleet MPG. For each jurisdiction, divide the miles driven there by that MPG to get taxable gallons, subtract the tax-paid gallons bought there, and multiply the result by that jurisdiction's rate. Add the lines together. A negative line is a credit against the others.
Where do I find current IFTA tax rates?
IFTA, Inc. publishes a fuel tax rate matrix for each quarter at iftach.org, and base jurisdictions point filers to it. Rates can change every quarter and differ by fuel type, so this calculator does not store any. Copy the rate for your fuel and quarter, and check surcharge lines too.
Who has to file IFTA?
Carriers running qualified motor vehicles across member jurisdictions. Under the IFTA Articles of Agreement, that means a vehicle with two axles over 26,000 lb or 11,797 kg, three or more axles at any weight, or a combination over 26,000 lb. Recreational vehicles are not included. Check with your base jurisdiction.
When are IFTA returns due?
On the last day of the month after each quarter ends: April 30, July 31, October 31 and January 31. If that day falls on a weekend or legal holiday, the next business day is the due date (IFTA Articles of Agreement R960). Late returns can owe interest and penalties.
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Sources
- IFTA, Inc. fuel tax rate matrix (current quarter rates)
- IFTA, Inc. fuel tax rate matrix, 4th quarter 2026
- New Mexico MVD-11262, IFTA quarterly return instructions (rev. 03/2026)
- IFTA Articles of Agreement (2026), R245 qualified motor vehicle
- Indiana DOR to IFTA, Inc.: surcharge tax repealed July 1, 2018
Disclaimer: For general information and planning. Tax rates and rules change and your situation may differ. Check the official source and a tax professional before you file. Not legal or tax advice.
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