IFTA fuel tax calculator for owner operators

If you run in more than one state or province, the International Fuel Tax Agreement (IFTA) asks you to file a quarterly return that settles fuel tax between jurisdictions. You owe each jurisdiction tax on the fuel you burned there. You already paid tax on the fuel you bought there at the pump, so the return is really a comparison of the two.

This calculator does that comparison. For every jurisdiction, enter the miles you drove, the gallons you bought and the tax rate per gallon. It works out your fleet miles per gallon, how many gallons you used in each place, the tax due, the tax already paid at the pump, and the net amount you owe or the credit you carry.

How the math works

1. Fleet MPG is total miles divided by total gallons bought.
2. Gallons used in a jurisdiction are that jurisdiction's miles divided by fleet MPG.
3. Tax due is gallons used times the rate. Tax paid is gallons bought there times the rate.
4. Net is due minus paid. A negative net is a credit.

Tax rates change, so type in the current rate for each jurisdiction from the official IFTA rate table or your base state's website. This tool does not store any rates and does not check them for you.

Worked example

You drive 1,000 miles in State A and 500 in State B, and you buy 150 gallons in A and 100 in B. Fleet MPG is 1,500 / 250 = 6.0. Say A taxes 0.30 per gallon and B taxes 0.40. In A you used 166.67 gallons, so tax due is 50.00, tax paid is 45.00, and you owe 5.00. In B you used 83.33 gallons, so tax due is 33.33, tax paid is 40.00, and you have a 6.67 credit. The net across both is a 1.67 credit.