How do I calculate IFTA?

Jason Forrest

If you have your own authority or are leased onto a company that requires you to file your own IFTA, chances are, you have to do the calculations yourself. 

Or maybe you are just curious about how it is done. 

In either case, there are six steps to follow to accurately calculate your IFTA tax.

I know IFTA can be scary and you may think there’s a lot of tedious math involved, but it really isn’t so bad if you follow the steps below.

Also, you only need to follow all of the steps in the worst case scenario, which is: you’ve decided to file your IFTA return by hand and your state doesn’t have an online IFTA filing portal.

Before you start, here’s how you can make IFTA easier on yourself

First, you can use a tool like Rigbooks that will do the calculations for you. 

Since you’d already want to enter your fuel receipts and state-to-state miles as you go—or import them to skip having to enter them by hand—when it comes time to file your IFTA return, you can just run a report with the push of a button.

Second, you can use an ELD that provides an IFTA reporting feature, like KeepTruckin.

Third, you can hire an accountant to do your IFTA filing.

If none of these are an option for you, or you just want to do it yourself, then read on and I’ll tell you what you need to do.

What you’ll need


Before we get into the nitty gritty details of how to calculate your IFTA return, here’s what we are doing at a high level:

Your IFTA fuel tax is calculated based on how many gallons of fuel you burnin each state.

We won’t know that upfront, so we will have to calculate it based on what you do know.

  1. You know how many miles you traveled in each state.
  2. You know how many gallons you purchased in each state.
  3. You’ll need to calculate your fuel mileage over the entire quarter.
  4. You’ll need to calculate your total gallons burned in each state using the results from Steps 2 & 3.
  5. You’ll need to calculate your tax owed in each state.
  6. You’ll need to calculate the total amount owed on your IFTA return.

Step 1

Remember all those miles that you have been tracking from state line to state line? Those are about to come in really handy.

If you were tracking your miles manually, you will need to add those up for each state or Canadian province in which you have traveled during the previous quarter.

If you were using a GPS, ELD, or routing software that kept track for you, you need to find the device’s report that gives you the total miles traveled for each state. This may be part of a web portal they provide as a service.

You’ll also need to total all miles driven in all states during the quarter for Step 3. 

You can do this by adding up all the miles for each state or subtracting the odometer reading from the beginning of the quarter from the odometer reading at the end of the quarter.

Step 2

Next, add up all the gallons of fuel you purchased in each state. You will also want to keep a running total of all gallons purchased in all states during the quarter for Step 3.

If you have a pile of fuel receipts, this part will not be much fun. You’ll need to go through each receipt and add the gallons purchased to the total for the state as well as the running total.

If you are using a fuel card, they may provide a report that gives you this information when you log into your fuel card account.

If you are using Rigbooks trucking software, it will add all this up for you so long as you enter the state purchased when you enter your fuel receipts.

Important note! If your state has an online IFTA return filing portal, you can stop here. All they require you to enter is the state-to-state miles and the total gallons purchased per state and they calculate the rest of the return for you.

Step 3

You need to know your fuel mileage across all states for the entire quarter (to two decimal places) in order to complete Step 4.

You calculate the fuel mileage for the entire quarter like this:

	Total Miles Driven in All States ÷ Total Gallons Purchased in All States = Overall Fuel Mileage

You should have already calculated the Total Miles Driven in All States from Step 1, and the Total Gallons Purchased in All States from Step 2.

Step 4

Now, calculate your gallons burned in each state.

Total Miles Driven in Each State ÷ Overall Fuel Mileage = Gallons Burned in that State

You will need to do this for every state you traveled in—even if you didn’t buy any fuel there.

Step 5

Then you will calculate the fuel tax required and the fuel tax you already paid to each state (at the pump). 

Use the rates table at to get the latest fuel tax rates for each state. 

Calculate the tax required for each state, based on the gallons of fuel you burned there. You will use the results from Step 4.

	Total Gallons Burned in Each State x Fuel Tax Rate for that State = Fuel Tax Required for that State

Some states also have a surcharge (currently Indiana, Kentucky, and Virgina). To calculate the surcharge tax owed:

	Total Gallons Burned in Each State x Surcharge Rate for that State = Surcharge Required for that State

Next, calculate the fuel tax paid for each state, based on the results from Step 2.

	Total Gallons Purchased in Each State x Fuel Tax Rate for that State = Fuel Tax Paid for that State

Finally, you calculate how much tax you actually owe for each state:

	Fuel Tax Required for Each State – Fuel Tax Paid in that State = Fuel Tax Owed to that State

Some of these values may be negative, which means you bought more fuel in that state than you burned, and therefore you paid more in fuel taxes to that state than you were required to pay. 

If that’s the case, you won’t get a refund from each state. You just add it all up across all states for your IFTA return, which is Step 6.

For states that charge a surcharge, you will not have paid the surcharge until you file your IFTA return, so it will never be a negative amount.

Step 6

Now you need to calculate the total amount owed on your IFTA return.

To do this, just add up all the Fuel Tax Owed to Each State values from Step 5. Some of them may be negative and you subtract those amounts from the total.

Now what?

If your state has an online IFTA filing portal, you can just enter the totals you got from Steps 1 & 2 into the portal and it will calculate your IFTA return and tell you what you owe.

If your state requires a paper filing, then you will need to enter the values from each of the 6 steps above into the appropriate places on the form they provided. 

Some of the states’ forms will have all the states listed out for you and others will have you write in only the states you actually traveled in.