How the IFTA calculation works
IFTA settles fuel tax by the miles you drive in each jurisdiction, not by where you buy fuel. The calculator follows the same steps as the quarterly return:
- Fleet mpg = total miles ÷ total gallons bought, across all jurisdictions.
- Taxable gallons in a jurisdiction = miles driven there ÷ fleet mpg.
- Tax due = taxable gallons × that jurisdiction's rate for the quarter.
- Tax paid = gallons bought there × the same rate.
- Net = tax due − tax paid. A positive net is owed; a negative net is a credit.
Your base jurisdiction adds the nets together, collects what you owe or credits what you're owed, and settles with the other states for you.
Rates are prefilled from the IFTA, Inc. matrix for 4Q 2026, using the special diesel rate plus any surcharge the matrix lists separately (for example, Kentucky and Virginia). Change any rate if you are working on a different quarter.
Source: IFTA, Inc., IFTA tax rate matrix, 4th quarter 2026 · checked Oct 2026
A worked example
EXAMPLE
Made-up carrier. 4Q 2026 rates.
Carrier A filled up only in Texas. Texas collected tax on 1,600 gallons at the pump but only 960 gallons were burned on Texas roads, so Texas owes a credit. Oklahoma collected nothing at the pump but got 640 gallons' worth of miles, so Carrier A owes Oklahoma. Here the two nearly cancel out. Buy most of your fuel in a high-tax state and drive mostly in low-tax states and the credit grows; do the opposite and you owe.
What a good and a bad result look like
There is no "good" IFTA number in itself; the tax is the tax. What the result tells you is whether your records make sense:
- A small net either way is normal for a truck that buys fuel along its routes.
- A large amount owed usually means you are buying fuel in low-tax states and driving many miles in high-tax ones. That can still be the cheaper choice at the pump; see the where-to-fuel calculator before changing habits.
- A fleet mpg that looks wrong (far above or below what the truck really gets) points to missing fuel receipts or missing miles. Fix the records before you file; an auditor will check the same number.
Keeping records the return depends on
Miles by jurisdiction come from your ELD or trip sheets; gallons come from fuel receipts and fuel card statements. A running log saves the end-of-quarter scramble: the IFTA mileage and fuel log keeps both in one place. For the current rate and filing portal in every state, see IFTA tax by state; for how rates have moved, see IFTA fuel tax rates history.
Fuel tax is also a reason to look at where you fill up. The where-to-fuel calculator compares pump prices and tax by state along a route.
Fuel in every load
IFTA is a quarterly bill, but fuel is a daily cost. Our dispatch service for owner-operators books loads with fuel in the math: the surcharge on the rate con, the empty miles to the pickup, and the reload. Send an application and a dispatcher calls you back.
General information, not tax advice. Rules and rates change every year and depend on your situation: confirm with a tax professional before you file. We are not a tax preparer or accountant.
Questions about this calculator
How do you calculate IFTA?
Divide total miles by total gallons for your fleet mpg. For each jurisdiction, divide its miles by that mpg to get taxable gallons, multiply by its rate for the quarter to get tax due, multiply the gallons you bought there by the same rate to get tax paid, and subtract. Add the nets for the quarter.
How do I calculate taxable miles for IFTA?
Taxable miles are generally all the miles a qualified vehicle travels in a jurisdiction, loaded or empty, including deadhead and personal-conveyance miles in that vehicle. A few jurisdictions treat certain toll-road or off-road miles differently; your base jurisdiction's instructions say how to report them.
How do I calculate tax-paid gallons for IFTA?
Add up the gallons you bought at retail in each jurisdiction where the fuel tax was included at the pump, using receipts or fuel card statements. Fuel bought in bulk or without the tax included is reported differently. Keep every receipt: tax-paid gallons without a receipt can be disallowed in an audit.
Where do the rates come from?
The calculator prefills each state's special diesel rate, plus any surcharge listed separately, from the IFTA, Inc. tax rate matrix for 4Q 2026. Rates change quarterly, so for another quarter change the rate in the row to the one on the matrix for that quarter.
Is there an IFTA calculator app?
This calculator works on a phone browser with nothing to install, and your rows are saved on your device between visits. Use Copy result link to save a quarter, or print it for your records. Most ELD and fleet apps also produce IFTA mileage reports you can enter here.
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Updated October 2026. Every rate and date on this page has its source and the date we checked it. How we research