PMPer Mile Math

IFTA Fuel Tax Calculator

Enter the miles you ran and the fuel you bought in each jurisdiction. This returns your net amount due — or your refund — for the quarter, plus the per-jurisdiction breakdown so you can check it line by line.

Using — rates · — jurisdictions · Source: official IFTA matrix

Quarterly return

Loading rates…

Most heavy trucks settle on the diesel rate.

Check before you file. This calculator reproduces the standard IFTA quarterly calculation, but your carrier or state may apply rules this page does not model — split-quarter rates, fuel tax holidays, or per-vehicle MPG instead of fleet average. Treat the output as a cross-check, not as your filed return.

How the IFTA calculation actually works

IFTA does not tax you on where you bought fuel. It taxes you on where you burned it. Every jurisdiction wants its share of the fuel you consumed on its roads, and it collects that share by comparing the fuel you should have burned there against the fuel you actually bought there.

  1. Fleet average MPG. Total miles for the quarter divided by total gallons purchased. Every jurisdiction is settled at this one rate.
  2. Gallons taxed in each jurisdiction. Miles run in that jurisdiction divided by your fleet MPG. This is the fuel you should have burned there.
  3. Net gallons. Gallons taxed minus gallons you actually bought there. Positive means you burned more than you bought — you owe that jurisdiction. Negative means you bought more than you burned — that jurisdiction owes you.
  4. Tax. Net gallons multiplied by that jurisdiction's rate for the quarter.
  5. Net due. Sum every jurisdiction. One number goes on the return.

This is why a driver who fills up in a low-tax state before crossing into a high-tax state can end up owing money even though they bought plenty of fuel. It is also why the rate table matters more than the arithmetic — the formula is simple, the rates are what change.

Common ways people get this wrong

  • Using state excise tax rates instead of IFTA rates. They are different numbers. IFTA rates settle tax between jurisdictions; excise rates are what a state charges at the pump.
  • Using last quarter's rates. Rates are fixed per quarter. Filing Q3 against Q2 rates produces a wrong return even if every mile is right.
  • Forgetting a jurisdiction entirely. One missed state is the most common cause of an amended return.
  • Mixing per-vehicle MPG with fleet average. Pick one method and apply it consistently across the year.

Questions

Do I have to file IFTA every quarter, even with no tax due?

Yes. A quarterly return is required even when the net result is zero or a refund. A zero return and a missing return are not the same thing.

Which MPG method should I use?

Most small carriers use fleet average, which is what this calculator does. Per-vehicle MPG is allowed but must be applied consistently and is more bookkeeping than most one-truck operations need.

Why does a jurisdiction show no rate?

Some jurisdictions do not impose an IFTA fuel tax on a given fuel type. Oregon, for example, does not levy an IFTA fuel tax and instead applies a weight-mile tax. Where a jurisdiction reports no rate, this site shows it as unavailable rather than substituting a number.

Are these rates the same as what my fuel card reports?

They should reconcile to the same official matrix, but fuel cards sometimes show effective rates that include their own fees or discounts. Always compare against the published matrix, not a card statement.

Rate data: —. Rates are republished for reference and are not a substitute for the official matrix at iftach.org.