Free IFTA Fuel Tax Calculator

Quarterly IFTA tax by jurisdiction — owed or credit, in seconds

100% FREE · NO SIGNUP · NO TRACKING

Rates: Q2 2026 (Apr–Jun) · diesel · source: iftach.org

Estimate only. IFTA rates change quarterly — verify against the official rate sheet at iftach.org before filing. This tool covers diesel and is not tax advice.

Step 1 · Your fleet totals (this quarter)

Fleet average MPG: — (total miles ÷ total gallons)

Step 2 · Miles & gallons per jurisdiction

Jurisdiction Miles in jdx Gallons bought Tax rate ($/gal) Taxable gal Tax due Tax paid Net

Result

Add jurisdictions and press Calculate IFTA to see your net tax by state and the total owed or credit.

How to calculate IFTA (the math this tool runs)

The International Fuel Tax Agreement (IFTA) makes you pay fuel tax based on where you burned the fuel, not where you bought it. Here is the exact calculation, per jurisdiction:

  1. Fleet MPG = total miles in all jurisdictions ÷ total gallons purchased everywhere.
  2. Taxable gallons = miles driven in jurisdiction ÷ fleet MPG (the fuel you consumed there).
  3. Tax due = taxable gallons × that jurisdiction's tax rate.
  4. Tax paid = gallons purchased in jurisdiction × the same rate (credit for tax already paid at the pump).
  5. Net = tax due − tax paid. Positive = you owe; negative = you get a credit. Sum every jurisdiction for your total.

Worked example: 1,000 miles in a state at 6 MPG with a $0.30/gal rate and 100 gallons bought there → taxable gallons = 166.7, tax due = $50.01, tax paid = $30.00, net owed = $20.01. (Taxable gallons are rounded to tenths, the figure carried onto the return; some jurisdictions round to whole gallons, so confirm your state's form.)

IFTA FAQ

When is IFTA due?

IFTA is filed quarterly. Deadlines are the last day of the month after each quarter: April 30 (Q1), July 31 (Q2), October 31 (Q3), and January 31 (Q4). If a deadline lands on a weekend or holiday it moves to the next business day. You must file even if you owe nothing or ran no miles that quarter.

What are taxable gallons?

Taxable gallons is the fuel your trucks burned operating in a jurisdiction — miles driven there divided by your fleet MPG. It's the fuel you used, which differs from the fuel you purchased there. IFTA reconciles the two so tax lands in the state where the fuel was consumed.

Why do I owe in one state but get a credit in another?

If you drove a lot of miles in a state but bought little fuel there, you owe (you used more tax than you prepaid). If you fueled up heavily in a state but drove few miles, you've overpaid and earn a credit. Your net return is the sum across all jurisdictions.

Do these rates change?

Yes — IFTA tax rates are set per jurisdiction and can change every quarter. The official table is published by IFTA, Inc. at iftach.org before each quarter. This calculator embeds the Q2 2026 diesel rates; always confirm the current quarter before filing. Where a rate isn't applicable (e.g. Oregon's weight-mile system), the field is editable so you can enter the correct figure.