IFTA calculator
Enter your miles and your fuel by state. See the fuel tax you owe for the quarter, or the credit you get back.
Your IFTA fuel tax
- Total miles
- 26,000
- Total gallons bought
- 4,000
- Fleet MPG
- 6.50
- Net IFTA tax due
- $16.63
How to use this calculator
Enter one line for each state you ran in during the quarter. The calculator works out your fleet MPG and what you owe each state.
- Quarter. Pick the quarter you are filing. The diesel tax rates load for that quarter.
- State. Add every state you drove in, even a state where you bought no fuel.
- Miles driven. All miles in that state, loaded and empty. Your ELD or your trip sheets have the count.
- Gallons bought. Diesel you bought in that state with the tax paid at the pump. Your fuel receipts have it.
The boxes start with example values, so change every one of them to your own.
How IFTA fuel tax is calculated: a worked example
IFTA charges you for the fuel you burned in each state, at that state's rate. Then it gives you credit for the tax you paid at the pump there.
- Divide your total miles by your total gallons. That is your fleet MPG.
- Divide your miles in each state by that MPG. That is your taxable gallons for the state.
- Subtract the gallons you bought in that state.
- Multiply what is left by the state's tax rate.
Here is that math with the calculator's starting numbers: 26,000 miles and 4,000 gallons, so 6.50 MPG.
| State | Miles | Taxable gallons | Gallons bought | Rate | Tax or credit |
|---|---|---|---|---|---|
| Texas | 12,000 | 1,846 | 3,200 | $0.2000 | $270.80 credit |
| Oklahoma | 6,000 | 923 | 0 | $0.1900 | $175.37 due |
| Kansas | 8,000 | 1,231 | 800 | $0.2600 | $112.06 due |
| Total | 26,000 | 4,000 | 4,000 | $16.63 due |
You bought 3,200 gallons in Texas and burned 1,846 there. Texas owes you a credit of $270.80.
You burned 1,231 gallons in Kansas and bought only 800 there. You bought none in Oklahoma. You owe those 2 states $287.43.
Net, you send your base state $16.63. The tax follows the miles, not the pump. So when you compare 2 fuel stops, take the state tax out of each pump price first.
IFTA due dates for 2026
Your IFTA return is due the last day of the month after the quarter ends. If that day is a Saturday, a Sunday or a legal holiday, the next business day counts.
| Quarter | Miles and fuel from | Return due |
|---|---|---|
| 1st quarter 2026 | January to March | April 30, 2026 |
| 2nd quarter 2026 | April to June | July 31, 2026 |
| 3rd quarter 2026 | July to September | November 2, 2026. October 31 is a Saturday. |
| 4th quarter 2026 | October to December | February 1, 2027. January 31 is a Sunday. |
File every quarter, even one with no miles. A late return costs the greater of $50 or 10% of the net tax due, plus interest. That is the rule Florida's IFTA office publishes.
What the numbers mean
The net IFTA tax is the headline. In the example it is $16.63 due. A credit shows when you paid more at the pump than you owed.
- Fleet MPG is your total miles divided by your total gallons, rounded to 2 decimals. Every state uses the same MPG.
- Taxable gallons is the fuel you burned in a state: your miles there divided by your MPG.
- Tax or credit is taxable gallons minus gallons bought, times the state rate.
- Net IFTA tax is every state added together. You send 1 payment to your base state, or get 1 refund.
Kentucky and Virginia add a surcharge on every taxable gallon. Fuel you bought there does not reduce it, and the calculator adds it for you.
Oregon has no IFTA diesel rate. Still enter your Oregon miles and fuel, because they count toward your MPG.
This calculator treats every mile as taxable and covers the 48 states, not Canada. Some states carry footnotes on the IFTA matrix, so check your states there before you file.
This is an estimate, not tax advice. Your base state's return is the official number.
Next step: fuel tax is one part of your fuel bill. See the whole bill per mile in the fuel cost calculator.
Questions drivers ask about IFTA
What is IFTA?
IFTA is the International Fuel Tax Agreement. The 48 contiguous states and 10 Canadian provinces use it to collect fuel tax together. You file one return each quarter with your base state.
Who needs an IFTA license?
You need one if you run a qualified motor vehicle in 2 or more member states. That means 3 or more axles, or a weight over 26,000 pounds, alone or in combination.
How do you calculate IFTA tax?
Divide your total miles by your total gallons to get your MPG. Divide each state's miles by that MPG, then subtract the gallons you bought there. Multiply the result by the state's tax rate.
When is IFTA due?
The last day of the month after the quarter ends: April 30, July 31, October 31 and January 31. A weekend or legal holiday moves it to the next business day.
Do I have to file IFTA if I did not run?
Yes. A return is due every quarter, even with no miles and no fuel bought.
Why do I owe IFTA when I already paid tax at the pump?
You paid the tax of the state where you fueled. IFTA moves it to the states where you burned the fuel. If those states charge more, you owe the difference.
What is the penalty for filing IFTA late?
The greater of $50 or 10% of the net tax due, Florida's IFTA office says. Interest is added each month on top.
Sources, checked October 10, 2026:
- IFTA Inc. tax matrix and carrier information
- Florida Highway Safety and Motor Vehicles, due dates and penalties
- South Carolina DMV return instructions, the method
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